On-grid domestic battery storage

zeupater

joefizz wrote: »

Agreed. Hence my post. Its not currently about making money, however my post was aimed at the posts about losses, cash etc etc. What my post does highlight as subsequent posters point out is that if you have the money in the bank and can spend it, it will improve cashflow significantly and allow other means of moneysaving that would have been moneycosting. If I were making a similar post on another forum I wouldnt make half the statements I made above.
My point is that whilst I dont realistically expect to see a complete ROI on the battery system, it will allow me to save money elsewhere in things that dont usually get mentioned (hence the comment about going back to using my old electric lawnmower rather than the petrol one). Its not a big deal but its more about moving forward overall.
I'll reiterate, not only do I not expect the battery system to pay for itself, I expect to replace, upgrade, supplement it as time goes on.
Each year so far I have reinvested my Fit payment and some of the electricity cost savings into producing my 'system'. I then expect a possible 5 year period of stasis (unlikely in my scenario) and then perhaps the upgrade/maintenance on the system.
I bought this house (my first) 24 years ago and paid it off 5 years ago and am going nowhere ;-) So again thats a factor in my choices.
As I also mentioned I work and run my business from home, Ive had one power out for 12 hours in the last year and the battery system enabled me to continue to work, thats not really a cost you can realise in spreadsheets but even the peace of mind of that is worth the cost of the battery install (Ive spent smaller figures in the past on UPS equipment with 30 mins time).


...


Wood for the trees. Yes 200 quid is less than 2.2k but again its viewed as a system. If the DHW was my only consideration then possibly but again it wouldnt meet my requirements. I dont need hot water on all the time or indeed require it at specific times during the day night so a quick push button from a battery (whilst the battery is installed) completely meets my requirements.
Again I point out (as below) Im only giving my individual standpoint and comparing it with yours is pointless. Im giving another view.

...

As I said above, thats not a justification point, its one of the things about owning the system once the decision is made. As I mentioned in my post the energy market here in NI is all ireland, back in July the generators, suppliers and regulators had no idea what was going to happen at 11:01pm on 29th March (yeah I know!) so it was more a business decision to protect my business. It wasnt scaremongering as all the small scale renewables here are purchased by a company in dublin and even knowing what level of vat/duty/whatever to charge was unknown so a lot of the wind turbine people were talking about just turning them off until they knew they were actually going to get paid. The electricity suppliers here are mostly owned by Irish companies... One of the main power stations here in NI was to be shut down in Sept as being uneconomically viable (as well as dirty) but has been kept going because noone knows whats going on. Add in a winter storm with snow like last year (the uk was about 2 days from running out of gas IIRC) and suddenly a couple of grand for a battery system is really really cheap.


....

No standing charge. See my points above about extrapolating your circumstances onto mine. Im just giving a different viewpoint. My solar installer recommended going with economy 7 when I got the batteries so I could charge at night in winter. Well the standing charge alone would probably double my annual electricity bill without.
I redid my house a couple of years ago and uprated insulation, put in led lights throughout, energy saving kettles, all a++ rated appliances etc etc etc. My average usage per day is about 6kWh. Jan I generated a little under 80kwH, Feb around 200kWh, March was 332 kWh. Due to my work I generally get to take my holidays in Jan so was away for a week then.
Moving two of the E/W panels to orientate solely for Dec/Jan usage might just cover the difference or a large part of it.

As I said above, it suits my circumstances. This year I'll be away June/July and next year probably away all of January, so my generation in summer will be pretty much all export and in Jan there will be little or no import.

Not everyone is as flexible as I am but if you are you can now see where it meets my requirements.
If you have a family of 5 then I doubt its going to work for you...

....

Yep just under 5k for initial install, 2.2k for pylontech 4.8kw and me3000sp, 1.2k for extra panels and gubbins and 1.6k for 2 extra pylontech batteries so pretty much the 10k I quoted at the start of my post.
NI rocs plus export is around 500-600 (again need another full year with the new panels for proper figures) and electricity saving per year is around 2-300, oil saving cost perhaps 100-150 but loss of income on the savings is about the same as that.
Essentially there is a grand a year Im not having to pay out (or more) by using this system and considering when I installed it electricity here was 13p a unit and now its 17p a unit...
I paid about 550 for the ashp and as it is still sitting in boxes in my hall I havent mentioned it because will need a full years data (dont intend to use it during winter just mid March to mid Oct say)

...

As I said above, it works for me and doesnt work for you. Im not saying my setup will work for you as clearly it wont. 1kWh per day in Jan sounds horrendous, my worst January generation was 48Kwh (Jan 2018). So yes as I quoted the figures above I should have excess generation in my system optimistically from mid Feb right through to the last week in Nov. Dec is my low month and before the new panels struggled each year with only around 30kwh generated in total. 50 this december with the new panels so a couple oriented completely for mid nov to mid jan might cover this but only makes economic sense if I use a couple of the e/w panels as I will probably top out sometime May/Jun and want to see which ones I can move with no real effect for the rest of the year (battery/export balance etc).
When I planned the south facing panels I had originally planned to make them tilt and would tilt them 3 times a year which would cover the shortfall. However climbing onto the garage roof to tilt them in Jan wouldnt have been a great idea. I did make the rails in a way that this can be done so I may motorise those at some point in the future as another garage weekend project (probably use a drill to turn a screw mechanism or something rather than a permanent motor drive fixture). Although I might just pick an optimum angle and leave it there if it works.

Hi

I appreciate your post, but there are still issues that don't stand up to logic that could maybe be clarified ... however, before doing so ...

... The 1kWh you've picked up from January isn't what you seem to have understood ... it's stated as being 'kWh/kWp', so not quite as horrendous as you thought ... however, as stated, in context "we (like many other PV owners) struggle to generate anywhere near an average of 1kWh/kWp per day in January" ...

... We are also extremely low importers of electricity with PV and high efficiency appliances with daily electricity imports for the previous rolling 12 months being ~3kWh/day, with a range of 2.1kWh/day in Q2 to 4.5kWh/day in Q4 ... January & December both requiring just over 5kWh/day imports ....

... We have a no standing charge fixed rate renewable energy tariff, so all-in-all quite similar to what you've described therefore the effect of extrapolation errors due to misunderstanding should be considered as being somewhere between non-existent & extremely low if relevant variables were to be disclosed ... so, that said, let's move on ...


In January you stated generation as being 80kWh which represents 0.5kWh/kWp/day on a 5.2kWp system, your average usage is 6kWh/day, electricity is now 17p/kWh (with no standing charge) and you were away on holiday for 1 week.... ?

Okay, batteries aside ... your standard usage for 24 days was around 144kWh (24x6) and assuming you turned everything except the usual appliances off (fridge, freezer, frost-stat heating controls, battery management system etc) and that accounted for (say) 21kWh (7x3) then we have a basic imported energy calculation resulting in energy imports for January alone of of 85kWh ((144+21)-80), which at 17p/unit in a perfect world (where there are no exports!) resolves to a bill of around £14-£15 ... that's 75% (15/20) of the energy bill for the entire quarter and only achievable because due to a previously undisclosed week's holiday, which if excluded would equate to a bill in excess of £18!

So, we're now left with between £2(12kWh) & £5(30kWh) to spread over February & March where daytime PV generation excess brings the batteries into play ....

For February the generation was stated to be 200kWh (1.37kWh/kWp) which is >25% lower than our own when size adjusted, and against this we have 168kWh of demand (6x28), initially describing an excess of 32kWh, from which battery round trip efficiencies etc must be applied - at 85% efficiency on an assumed(!) 50% diverted the loss would account for half of this figure .... but the main issue is the effect of consecutive poor generation days on battery depletion and how the battery recovers to a position where it covers the 6kWh daily demand over the following period ... as you say, every site is different, but I've just checked the generation of a number of systems around yours in NI on PVOutput and the daily variability & poor solar performance looks similar to what we experienced here during early February and an initial quick assessment of both our own generation & that of a system in NI suggests that we'd both have had to import around 10kWh over the first week in February, excluding round trip efficiencies .... that's it, including efficiencies etc as described, the £20 as billed has been eaten well before mid February, leaving nothing for other consecutive poor generation days in the remainder of the quarter, particularly those apparent in the first half of March ...


You must appreciate, I'm all for battery systems, but I'm adamant that anyone looking to have a battery system should be aware of the capabilities. On such things I naturally approach what I hear, see & read with an initial sanity check and if alarm bells ring conduct a rigorous forensic approach which requires the application of logic and detailed data, which is so often withheld ... I appreciate what you have added to the discussion, but must conclude that the data supplied describes such a marginal position before weighting winter demand (thus increasing 6kWh/day for winter & reducing that for summer!), that there is still something quite substantial missing ....

... maybe a bad day for logic, but maybe not ....

HTH
Z

joefizz

zeupater wrote: »

Hi

... maybe a bad day for logic, but maybe not ....

HTH
Z

OK let me make this really really simple for you....

Thats my bill for the last quarter with 5 quid DD discount and 5 quid customer loyalty discount.
Any more questions? ;-)
As I mentioned in my posts I deal in real terms, not estimates, not round trip losses, not annual averaged daily use applied per month, nothing. There it is in black and white and blue and green. 20.51 electricity bill for the last quarter. ROCs for the last quarter should be in the region of 69-70 quid.
Bill for the same time last year was 70 quid (but again not like for like with extra panels and battery) Jan 2019 to Jan 2020 will be the first full stable year.

joefizz

Apologies for the double post but this didnt tag on the end of my previous post.

zeupater wrote: »

I appreciate what you have added to the discussion, but must conclude that the data supplied describes such a marginal position before weighting winter demand (thus increasing 6kWh/day for winter & reducing that for summer!), that there is still something quite substantial missing ....

The bit you are missing is what Ive highlighted in previous posts, your calculations make assumptions based on your experience and your understanding. You make the massive assumption that my winter weighting demand is the same as yours. It obviously is not. I sort of hinted at that in my previous posts where I said I usually take all of Jan for my holidays (but not the last 2 years so have comparable data). My work is weighted towards summer so I use far more electricity in the summer months than the winter ones. Again as I hinted enough another couple of panels angled for December might see me through those months with normal usage and if it tops out in May/June I can just use two from the E/W facing to balance out.
Its not hard to see how some peoples winter weighting is reverse to others, but unless you actually have experience of it I can see its hard for you to understand.



Again at the risk of repeating myself endlessly, just because the battery system doesnt work for you and your usage, doesnt mean it wont work for others and no amount of guesstimates and extrapolations/interpolations will 'prove' that what works for me, doesnt.

zeupater

1961Nick wrote: »

Hi Z

If you have another read of my post you'll see that the 5.9% & 9.8% are reductions in consumption ~ I think "import + solar usage" is clearly stated? This being the case, the level of solar production is largely irrelevant.....I say "largely" because round trip losses are recorded as 'usage' by the energy monitor. I'm sure you can see the implications of that on the data.

I really am at a loss as to why you're trying to reconcile my 117% of PVGIS in Feb 2018 with Legoman62's Jan 2016 PVGIS? If you continue to have "considerable issues" I may be able to cast some light (pun intended) on your dilemma.:)

For the record, my batteries were commissioned on 29/01/2019. The solar inverter, which failed on 30/12/18, was also replaced on this date - hence the lack of generation in January 2019.:(

Hi

I think the point being made is relevant in that the difference in generation actually does have an effect on consumption if it's defined as 'import + solar usage' .... PV generation first satisfies direct demand, with any excess being exported, thus decent generating days reduce imports more than poor generating days .. (yes?) ... with a battery the difference is that, depending on the specification of the battery charge-rate capabilities, some, or all, of the the energy that would have been exported is diverted to the battery for later usage - however, if generation is poor then the battery charge state will be lower & depleted batteries increased rick of import .. (yes ?) .... so, isn't it the case that simply adding grid imports to battery supply doesn't equate to consumption? ...

Expanding on that, unless you're actually metering the solar generation which is being used in the house through reconciling the TGM, with both the an accurate battery circuit diversion/supply meter (ie not a current sensing clip!) and have an export meter, then how do you actually know what consumption actually is? ... as you've previously stated, you're already looking at installing bi-directional meter to battery system to improve accuracy, but haven't (?) mentioned how you currently meter overall consumption ... do you have an export meter or an export register enabled smartmeter?

On to reconciling the statements ... that's my mistake, apologies for the confusion ... I simply looked through the posting history on that thread & that was the first post prior to 17/03 this year ... I obviously saw the date was 2016 (even stated it!), but was probably already thinking about the logic involved in next post in line regarding this type of set-up ... thanks for the clarification, but at least it does go to show the variability of generation for a particular month between years and how this could seriously impact battery performance when PV conditions aren't as good! ...


HTH
Z

1961Nick

zeupater wrote: »

Hi

I think the point being made is relevant in that the difference in generation actually does have an effect on consumption if it's defined as 'import + solar usage' .... PV generation first satisfies direct demand, with any excess being exported, thus decent generating days reduce imports more than poor generating days .. (yes?) ... with a battery the difference is that, depending on the specification of the battery charge-rate capabilities, some, or all, of the the energy that would have been exported is diverted to the battery for later usage - however, if generation is poor then the battery charge state will be lower & depleted batteries increased rick of import .. (yes ?) .... so, isn't it the case that simply adding grid imports to battery supply doesn't equate to consumption? ...

Expanding on that, unless you're actually metering the solar generation which is being used in the house through reconciling the TGM, with both the an accurate battery circuit diversion/supply meter (ie not a current sensing clip!) and have an export meter, then how do you actually know what consumption actually is? ... as you've previously stated, you're already looking at installing bi-directional meter to battery system to improve accuracy, but haven't (?) mentioned how you currently meter overall consumption ... do you have an export meter or an export register enabled smartmeter?

On to reconciling the statements ... that's my mistake, apologies for the confusion ... I simply looked through the posting history on that thread & that was the first post prior to 17/03 this year ... I obviously saw the date was 2016 (even stated it!), but was probably already thinking about the logic involved in next post in line regarding this type of set-up ... thanks for the clarification, but at least it does go to show the variability of generation for a particular month between years and how this could seriously impact battery performance when PV conditions aren't as good! ...


HTH
Z

Last try......:D

(You are over complicating this.)

Consumption = Energy used by the house which is the sum of the import + solar not exported.

Solar production has negligible effect on the energy consumption (as defined above) of my house. Historically there was no effect but battery losses now have a small impact. This of course means that the figures I quoted are actually on the low side, but that actually makes my point more valid, not less!

The figure for import & solar production is obviously coming from the respective meters & should be accurate.

The export figure is taken from the energy meter which uses a clamp on the meter tail. I accept that this unlikely to be 100% accurate but the same clamp/monitor was used for the readings in 2018 & 2019.

The main reason for fitting a bi-directional meter to the battery inverter is to acquire accurate data for a future decision on a traffic light tariff. The economics of putting off-peak energy into the batteries might not be that straight forward if the 18% loss that you calculated is realised. There is also the capital cost of a battery cycle to consider as well.

zeupater

joefizz wrote: »

OK let me make this really really simple for you....

Thats my bill for the last quarter with 5 quid DD discount and 5 quid customer loyalty discount.
Any more questions? ;-)
As I mentioned in my posts I deal in real terms, not estimates, not round trip losses, not annual averaged daily use applied per month, nothing. There it is in black and white and blue and green. 20.51 electricity bill for the last quarter. ROCs for the last quarter should be in the region of 69-70 quid.
Bill for the same time last year was 70 quid (but again not like for like with extra panels and battery) Jan 2019 to Jan 2020 will be the first full stable year.

Hi

It's that simple that it's obvious from that snippet ... the standard discount for your supplier is 25% of whatever the billed amount, or there's a fixed £5 discount, the same applying for the loyalty scheme, so your effective cost per unit is 8.5p ....

Yes, I know it's crazy, but as opposed to the above I would have thought that the standard business approach in the energy supply sector would be something along the lines of (random NI supplier quarterly DD T&Cs) ...

Quarterly Direct Debit customers get 2.5% discount off the standard rate up to £6.50 per quarter equivalent to £26 per year. The maximum discount would be obtained by a customer spending £250 each quarter on electricity. The standard rate is 16.82p kWh Ex.VAT / 17.66p kWh Inc. VAT.

.. to avoid the business folding .....

Earlier you mentioned that you'd recently changed supplier and received a £75 welcome bonus ... so there's no possibility that it wasn't credited to the account within this latest quarter and is netted off the bill after ant spending discounts were applied .... ??

I'm surprised that a business would offer so much discount ... can you provide a supplier link to provide confirmatory assurance to anyone reading ...

HTH
Z

zeupater

joefizz wrote: »

... The bit you are missing is what Ive highlighted in previous posts, your calculations make assumptions based on your experience and your understanding. You make the massive assumption that my winter weighting demand is the same as yours. It obviously is not. I sort of hinted at that in my previous posts where I said I usually take all of Jan for my holidays (but not the last 2 years so have comparable data). My work is weighted towards summer so I use far more electricity in the summer months than the winter ones. Again as I hinted enough another couple of panels angled for December might see me through those months with normal usage and if it tops out in May/June I can just use two from the E/W facing to balance out.
Its not hard to see how some peoples winter weighting is reverse to others, but unless you actually have experience of it I can see its hard for you to understand.

Again at the risk of repeating myself endlessly, just because the battery system doesnt work for you and your usage, doesnt mean it wont work for others and no amount of guesstimates and extrapolations/interpolations will 'prove' that what works for me, doesnt.

Hi

Absolutely not ...

(i) Any seasonal weighting wasn't included in the logic, only referenced as being necessary at the end with example given ... this is pretty standard ... people tend to use more electricity for lighting as well as DHW & space heating in months which have a lower ambient temperature & shorter daylight hours ... the percentage may vary, but the logic is pretty sound ...

(ii) You mentioned 1 weeks holiday this January (after query!) & likely longer next year ... nowhere have any calculations been based on previous years where you have taken January off and that applies to there having been no calculations for next year either!

(iii) Future additional panels at whatever angle make no difference to historical data ...

(iv) Weighting usage towards summer due to work pattern may increase the summer demand relative to that experienced by the majority, but it doesn't decrease the summer/winter import ratio for non-work activities unless you work almost exclusively at night in the summer ... this being due to the longer daylight hours and consequential summer/winter PV generation ratio ...


Regarding understanding, as a low energy user that has made considerable energy efficiency improvement over a couple of decades, I can assure you that it's not hard for me to understand your posts, it's just that the level of understanding (hopefully for all!) is evolving ....

And on to "battery system doesnt work for you and your usage, doesnt mean it wont work for others" ... but you've already accepted that " for the majority of people at the current price points its just not realistic from a purely economic point of view" and that you approach is along ethical & continuity reassurance grounds .... however, you then attempt to defend the decision on the grounds that it saves money on grounds that most individuals not interested in the economics would stay well clear of .... for example, there are others posting on this thread that have 'invested' in battery systems fully knowing that it's a poor economic choice but are happy in what they're doing.

Earlier in the 'conversation' I wrote ...

No problem with anyone deciding to be an early adopter at all ... as long as passing readers are aware of realistic performance expectations it's their decision on how they justify their own purchasing decisions & what they do with their own money ...

... and I fully stand by it.

In economic terms, it's an incontrovertible truth that, on battery storage alone (not a complete solution), what currently doesn't work for us, with our setup and our level of consumption won't work for anyone else with a setup & energy consumption which comes anywhere close to what we achieve ... no matter what the difference in usage pattern .... it's simply a matter of cost & returns and the cost is currently far too high ....


HTH
Z

joefizz

Right last reply as Ive already given you all the data, you dont believe me despite the facts and short of giving you access to my account and tax returns and inside leg measurement...

zeupater wrote: »

Hi

Absolutely not ...

(i) Any seasonal weighting wasn't included in the logic, only referenced as being necessary at the end with example given ... this is pretty standard ... people tend to use more electricity for lighting as well as DHW & space heating in months which have a lower ambient temperature & shorter daylight hours ... the percentage may vary, but the logic is pretty sound ...

Nope, again incorrect. As stated before DHW is summer months only, oil fired central heating shoulder and winter months. Again its all been posted.
Again you are making assumptions and your logic may be sound for your situation but if your work pretty much is seasonal of which daylight hours is a factor then working longer (again I work from home and run my own business) and more often in more daylight is a given. In fact in winter (January, as december is quite busy up to Christmas) its a good time to get my normal ambient energy usage as its when I use business heavy use the least.

What is it about that that you still dont get? Doesnt matter, Ive said its my last reply, Im sure everyone else reading it now gets it.

zeupater wrote: »

(ii) You mentioned 1 weeks holiday this January (after query!) & likely longer next year ... nowhere have any calculations been based on previous years where you have taken January off and that applies to there having been no calculations for next year either!

I thought I did mention that due to my job I normally take my holidays in January but didnt this year and last so could use them for comparison purposes? 2017 I did have solar and no battery but can only use the solaredge recorded generation values because I was away and didnt use much. Again I mentioned this. Its all about comparing like with like real world values, not making assumptions and using published fiddle factors.

zeupater wrote: »

(iii) Future additional panels at whatever angle make no difference to historical data ...

Indeed but they can be used as a ballpark as 2017 and 2018 Januarys were within 10% of each other. 2019 January was 50% higher than the highest so either the weather was exceptionally different or the extra panels made the difference.

zeupater wrote: »

(iv) Weighting usage towards summer due to work pattern may increase the summer demand relative to that experienced by the majority, but it doesn't decrease the summer/winter import ratio for non-work activities unless you work almost exclusively at night in the summer ... this being due to the longer daylight hours and consequential summer/winter PV generation ratio ...

Thats a big assumption and an incorrect one. My equipment is on 24/7 during the summer and it isnt in winter, in fact in a lot of January it isnt on at all and I have no real way of ascertaining what non work ambient is (other than as mentioned above taking January usage into account).
Taking normal summer usage such as lawnmowing, air con, hot tub, power washer etc etc etc none of which get used in winter. As I mentioned in my posts the excess in summer is now being used in creative ways such as cooking, dehydrating and even doing a 23L home brew boil (8 hour days) twice a month in summer. Again all stuff you wouldnt bother with in winter.

Like my previous posts its about changing the mindset, its about doing changing when you do energy intensive tasks during the year.
Again I will reiterate for the slow learners, I chose my system because of my usage, not bought a system then complained when it didnt work for me. Thats the whole point of my posts, just because someones usage pattern doesnt make it work, it doesnt mean it wont work for others.
Run a hot tub for a month in summer then tell me that a battery is pretty useless ;-)

You really arent getting this at all, are you. I'll conclude you wont get it but other people reading probably will.

zeupater wrote: »

Regarding understanding, as a low energy user that has made considerable energy efficiency improvement over a couple of decades, I can assure you that it's not hard for me to understand your posts, it's just that the level of understanding (hopefully for all!) is evolving ....

True. As I said I redid my house years ago to low energy standards and reduced oil consumption from approx 2200 litres per year to half that. With the solar, battery and ashp Im hoping to get another 1/3 to a half off that as well.
I cant really reduce my electricity costs much more (or in reality energy import because costs increase with time) because mainly of cost and current planning restrictions. Thats not to say however that it wont be possible in 5 years time. My 14 roof panels are 285w and the side 4 are 300w each.

It may be possible to have 350w with increased efficiency in a few years but unless its all replaced or go three phase then Im not going to make any real money upgrading. Saying that though all we would need is the green deal equivalent here and it may be worth upgrading the incoming line to 3 phase and bolting on to the existing system.

zeupater wrote: »

And on to "battery system doesnt work for you and your usage, doesnt mean it wont work for others" ... but you've already accepted that " for the majority of people at the current price points its just not realistic from a purely economic point of view" and that you approach is along ethical & continuity reassurance grounds .... however, you then attempt to defend the decision on the grounds that it saves money on grounds that most individuals not interested in the economics would stay well clear of .... for example, there are others posting on this thread that have 'invested' in battery systems fully knowing that it's a poor economic choice but are happy in what they're doing.

Earlier in the 'conversation' I wrote ... ... and I fully stand by it.

In economic terms, it's an incontrovertible truth that, on battery storage alone (not a complete solution), what currently doesn't work for us, with our setup and our level of consumption won't work for anyone else with a setup & energy consumption which comes anywhere close to what we achieve ... no matter what the difference in usage pattern .... it's simply a matter of cost & returns and the cost is currently far too high ....
HTH
Z

Again, for you and I think we may be arguing at cross purposes but you have made a few points where you have said you think or want to have it proved to you (electric ireland by the way but the sign up bonus is long since gone, just the bog standard dd reduction of a fiver a year and a fiver 'retention fee' I got on the phone when I talked about leaving and unit cost of 16.99p for every unit, so again 20 odd quid in bill at 16.99p unit cost). It is actually working for me and in my situation if Id been cleverer the roi would have been less than 10 years. For example the shipping of the battery system was free (or 25 quid) in mainland uk but 150 quid to NI, the extra batteries were about 75 quid postage. I paid full VAT on those and on the extra panels and solaredge modules because it wasnt a new build. Theres probably about 500 quid (a years ROC) right there.

Thing is I didnt have the data at the time, the pylontech werent available in the uk for my install yada yada yada, plus I didnt have all the money in one go.


Again I'll reiterate I dont expect the battery system to pay for itself in pure electricity terms but I do now expect it to pay for itself in terms of what it allows me to do (as mentioned before going back to electric lawnmower, buying cheaper tools, not looking for solar powered stuff, using an ashp etc etc).
Its looking at the lifecycle and the follow on from having the system that makes the savings and whilst not directly attributable in Kwh, vars, ohms or whatever you want to use, its how the things are used that make the difference.
Thats been my point, and I'll go back to my first post about how not to get bogged down in the minutiae of figures but see what it can actually do for you and what changes you can make as a result of it. (did I mention the beer making and the hot tub? ;-))
Again to go back to one of your points about going down the energy efficiency route, I did exactly the same, and whilst getting away from my eco credentials the fact that for pretty much 9-10 months of the year I can store my energy from the sun and use it whenever means I dont have to pay extra for the energy efficient models and not feel bad about it. Sure I lose the 4p per kW export but the 70 quid I saved on the big freezer which is going to cost me now only a couple of quid a year to run (less than that because it stores meals made in summer/shoulder and they get eaten through the winter so its empty by Christmas) etc etc.
Thats my point, its about using what you have and that requires a different mindset, and I'll be the first to admit they are things I never even considered before I bought the battery system. The fact that I did see it wasnt in itself going to pay for itself made me go out and look for other ways it would save me money and I'm still finding new ones (such as the cheap chinese ashp) every couple of weeks/months.

zeupater

1961Nick wrote: »

Last try......:D

(You are over complicating this.)

Consumption = Energy used by the house which is the sum of the import + solar not exported.

Solar production has negligible effect on the energy consumption (as defined above) of my house. Historically there was no effect but battery losses now have a small impact. This of course means that the figures I quoted are actually on the low side, but that actually makes my point more valid, not less!

The figure for import & solar production is obviously coming from the respective meters & should be accurate.

The export figure is taken from the energy meter which uses a clamp on the meter tail. I accept that this unlikely to be 100% accurate but the same clamp/monitor was used for the readings in 2018 & 2019.

The main reason for fitting a bi-directional meter to the battery inverter is to acquire accurate data for a future decision on a traffic light tariff. The economics of putting off-peak energy into the batteries might not be that straight forward if the 18% loss that you calculated is realised. There is also the capital cost of a battery cycle to consider as well.

Hi

Long term maybe, but you're also bringing the battery into play ... you can (for example) either measure consumption directly by having the battery & PV connected to a separate consumer unit and then accurately metering all energy flow into the main home consumer unit, or you can accept that the variance in battery charge levels creates inaccuracy & uncertainty within the methodology you're looking to adopt and this increases as the time between readings decreases due to the effect of charge variability, for example (excluding efficiencies etc) ...

10kWh(TGM)+5kWh(Metered)-3kWh(Unidirectional clamp Monitored Export) suggests household consumption of 12kWh ....

Add a battery system ...

If the above is applied to battery system which is full the day before the same (/similar) result may apply ... however, if the battery was depleted a proportion of the TGM reading would have been diverted as charge ... 10kWh(TGM)+5kWh(Metered)-3kWh(Export)-5kWh(change in charge status) suggesting 7kWh household consumption ...

You have to ether measure the battery input/output accurately (which you are already looking to do), or measure & include the opening & closing battery charge levels into your calculation .... your post contents so far suggest that it's not the case, but can you confirm you are not doing this ....

Another consideration regarding your clamp based monitor .... does it continually monitor the mains voltage for variance and apply that to the energy it records or is the voltage a selectable variable? - mains voltage changes related to local grid demand & can vary by around (/up to) 5% over a day, which is normally okay if you're simply monitoring spot power, but can cause significant errors in metering energy ... furthermore, how does your clamp monitor handle meter side power factor - many appliances have a considerable affect on the apparent:real power ratio, for example, our microwave on standby consumes 2.5W, however in having a PF of 0.05 the apparent power (as measured by a clamp sensor) would register this as 50W, a potential metering error of over 1kWh/day caused by just one appliance! ... and yes, because of the effect on our clamp-based monitor readings (that's power monitor, not energy meter!), we do turn the microwave off at the wall ...

Regarding the battery system inefficiencies ... yes, it does make a considerable difference to the economics of using E7, that's effectively what I've been trying to convey for some time ... in moving to E7 there are two main considerations ... the usual increase in daytime tariff rates & the efficiency loss through the battery on the cheaper night-time rate ... if the losses are 18%, then you're effectively paying the equivalent of 22% (100/0.82) more per kWh used than the actual billed rate, which makes quite a difference to battery justification economics based on E7 or any other form of demand based reduced tariff periods ...


I really am not trying to sound like someone that is anti-batteries, however, you must appreciate that when attempting to discuss the relevance of the variables which must be considered if looking to cost-justify a purchase, a realistic approach which may not at first seem to conform to the initial understanding of others may come across as negativity ... I can assure you, it's simply conveying the realism that marketing brochures & sales teams tend to skip over in the narrative (but often publish somewhere in technical specification tables) as well as helping to steer the though processes required to assess likely difference between maximum performance specifications & real world operation, for example, maximum charge efficiencies & the real-world impact of charge power on battery resistance energy losses as heat ...

HTH
Z

zeupater

joefizz wrote: »

Right last reply as Ive already given you all the data, you dont believe me despite the facts and short of giving you access to my account and tax returns and inside leg measurement...

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Nope, again incorrect. As stated before DHW is summer months only, oil fired central heating shoulder and winter months. Again its all been posted.
Again you are making assumptions and your logic may be sound for your situation but if your work pretty much is seasonal of which daylight hours is a factor then working longer (again I work from home and run my own business) and more often in more daylight is a given. In fact in winter (January, as december is quite busy up to Christmas) its a good time to get my normal ambient energy usage as its when I use business heavy use the least.

What is it about that that you still dont get? Doesnt matter, Ive said its my last reply, Im sure everyone else reading it now gets it.

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I thought I did mention that due to my job I normally take my holidays in January but didnt this year and last so could use them for comparison purposes? 2017 I did have solar and no battery but can only use the solaredge recorded generation values because I was away and didnt use much. Again I mentioned this. Its all about comparing like with like real world values, not making assumptions and using published fiddle factors.

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Indeed but they can be used as a ballpark as 2017 and 2018 Januarys were within 10% of each other. 2019 January was 50% higher than the highest so either the weather was exceptionally different or the extra panels made the difference.

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Thats a big assumption and an incorrect one. My equipment is on 24/7 during the summer and it isnt in winter, in fact in a lot of January it isnt on at all and I have no real way of ascertaining what non work ambient is (other than as mentioned above taking January usage into account).
Taking normal summer usage such as lawnmowing, air con, hot tub, power washer etc etc etc none of which get used in winter. As I mentioned in my posts the excess in summer is now being used in creative ways such as cooking, dehydrating and even doing a 23L home brew boil (8 hour days) twice a month in summer. Again all stuff you wouldnt bother with in winter.

Like my previous posts its about changing the mindset, its about doing changing when you do energy intensive tasks during the year.
Again I will reiterate for the slow learners, I chose my system because of my usage, not bought a system then complained when it didnt work for me. Thats the whole point of my posts, just because someones usage pattern doesnt make it work, it doesnt mean it wont work for others.
Run a hot tub for a month in summer then tell me that a battery is pretty useless ;-)

You really arent getting this at all, are you. I'll conclude you wont get it but other people reading probably will.

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True. As I said I redid my house years ago to low energy standards and reduced oil consumption from approx 2200 litres per year to half that. With the solar, battery and ashp Im hoping to get another 1/3 to a half off that as well.
I cant really reduce my electricity costs much more (or in reality energy import because costs increase with time) because mainly of cost and current planning restrictions. Thats not to say however that it wont be possible in 5 years time. My 14 roof panels are 285w and the side 4 are 300w each.

It may be possible to have 350w with increased efficiency in a few years but unless its all replaced or go three phase then Im not going to make any real money upgrading. Saying that though all we would need is the green deal equivalent here and it may be worth upgrading the incoming line to 3 phase and bolting on to the existing system.
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Again, for you and I think we may be arguing at cross purposes but you have made a few points where you have said you think or want to have it proved to you (electric ireland by the way but the sign up bonus is long since gone, just the bog standard dd reduction of a fiver a year and a fiver 'retention fee' I got on the phone when I talked about leaving and unit cost of 16.99p for every unit, so again 20 odd quid in bill at 16.99p unit cost). It is actually working for me and in my situation if Id been cleverer the roi would have been less than 10 years. For example the shipping of the battery system was free (or 25 quid) in mainland uk but 150 quid to NI, the extra batteries were about 75 quid postage. I paid full VAT on those and on the extra panels and solaredge modules because it wasnt a new build. Theres probably about 500 quid (a years ROC) right there.

Thing is I didnt have the data at the time, the pylontech werent available in the uk for my install yada yada yada, plus I didnt have all the money in one go.


Again I'll reiterate I dont expect the battery system to pay for itself in pure electricity terms but I do now expect it to pay for itself in terms of what it allows me to do (as mentioned before going back to electric lawnmower, buying cheaper tools, not looking for solar powered stuff, using an ashp etc etc).
Its looking at the lifecycle and the follow on from having the system that makes the savings and whilst not directly attributable in Kwh, vars, ohms or whatever you want to use, its how the things are used that make the difference.
Thats been my point, and I'll go back to my first post about how not to get bogged down in the minutiae of figures but see what it can actually do for you and what changes you can make as a result of it. (did I mention the beer making and the hot tub? ;-))
Again to go back to one of your points about going down the energy efficiency route, I did exactly the same, and whilst getting away from my eco credentials the fact that for pretty much 9-10 months of the year I can store my energy from the sun and use it whenever means I dont have to pay extra for the energy efficient models and not feel bad about it. Sure I lose the 4p per kW export but the 70 quid I saved on the big freezer which is going to cost me now only a couple of quid a year to run (less than that because it stores meals made in summer/shoulder and they get eaten through the winter so its empty by Christmas) etc etc.
Thats my point, its about using what you have and that requires a different mindset, and I'll be the first to admit they are things I never even considered before I bought the battery system. The fact that I did see it wasnt in itself going to pay for itself made me go out and look for other ways it would save me money and I'm still finding new ones (such as the cheap chinese ashp) every couple of weeks/months.

Hi

DHW & Oil fired heating relative to ambient temperatures .... I've no idea why you're protesting so much about this, but please do consider the issue you're missing ... in the winter it's cold & in the summer it's warmer, so heating is required by most people during colder months ... you use oil fired space & DHW heating more in the winter than in summer ... oil & gas fired heating systems are normally pumped systems ... pumps use electricity (100W) .... the more hours the pump runs, the more electricity you use ... ergo, DHW & space heating during the winter generally consumes more electricity than in summer ... just 5 hours of pumping per day in January would equate to 500Wh, which alone represents a considerable proportion of average daily PV generation in January & often all of a day's production ...

.... add to this the effect of mains water supply temperature seasonality, which can vary by around (/up to) 15C ... in winter the duty on whatever heat source is used to raise DHW temperatures to 60C may therefore be 38%(55/40) higher, plus the potential for higher cylinder standing heat loss to the house itself.

Both of these are valid points which lead to generally higher winter energy consumption that the majority of people would experience, including those who would knock-back the heating system to a frost-stat setting to protect the property whilst on a winter break (as indicated but missed relevance ... 'frost-stat'!)

Regarding January holidays, I believe that the first time you mentioned this was after the initial query on PV/battery performance relative to billed demand .... after further query on the figures previous holidays encompassing the whole of January & plans for next year were raised, but they make no difference as we're considering one thing ... this year!

Believe me, I understand what you're saying, but in effect anyone could claim being energy efficient during any month by simply turning everything off at the mains switch and going on holiday ... this being the case both with & without battery or PV systems!

By 'not making assumptions and using published fiddle factors', shall we all consider that your recommendation to anyone considering the cost justification of a battery system (or any other device!) should ignore the manufacturer's own specifications, industry guidelines & performance related laws of physics, then just buy on faith or sales patter ?! ...

As previously mentioned, I've no problem with you or anyone else looking to purchase & install a battery solution doing so on business, ethical or interest grounds without cost justification ... what raises my eyebrows is that having stated that this was basically your approach you've expended so much effort in attempting to justify on a usage & cost basis ...

Again, as raised before, we have current posting members that have already/previously purchased their own battery solution on the basis of interest and personal ethics, fully accepting the poor economics. This is fine and should be applauded as we need early adopters to drive demand, but the reality for the majority is that some form of justification is needed ... it's not really the same as normal product choice - if someone wanted a new chair because it look comfortable, or a new TV because of features that's one thing, but all we're looking at is the source & path of the electrons we will be consuming and the relative cost of those electrons ... it's simply a move from service based electron supply with no capital investment to a capital intensive alternative, therefore, for most justifying, the capital should be amortised & written down in a similar way to that a business normally would do on any capital investment ... and that's where the detail (the 'minutiae of figures' you mention) is important ...


HTH
Z