On-grid domestic battery storage

EVandPV

Greetings folks, first post here after reading through some (it's big !) of this thread.
Here's our situation, we had pv installed in Jan 2012 just before the FIT started to reduce and when it was still 43p per kwh.
PV was the best investment we've ever made by far. We paid £8k back then for a 3kw system which has now paid for itself and we're now in profit by around £1200 per year.
We have an immersion controller which uses around 3kwh of generation on a good day.
I changed my car this year to a Zoe R110 with 40kwh battery, had a Zappi wall charger fitted and will be switching to Octopus Go when our current 1 year deal ends in December.
I'm now toying with the idea of home battery storage, hence my interest in this thread.
Someone mentioned ev battery life, I know of someone with a Zoe that's done 80k miles and the battery SOH is still at 100% ! That gives me encouragement enough to see a decent lifespan for a home battery.
Like most others on these type of threads though, I'm struggling to make the figures work.
The best price I've found so far is around £2500 fitted for a 4.8kwh system comprising of Pylon batteries and a Sofar ac coupled inverter.
This will involve some haggling over the hardwear which I will be sourcing myself and having a local installer fit.
Even at this price, I reckon the ROI will be around 7 years so it's difficult to sell to my other half. £2k or lower would make it a fair bit more attractive but I'm struggling to get the batts and inverter for less than that, let alone a fully installed system.
My question is, is it worth holding off in the hope battery prices will fall ?
Is it even likely they will fall anytime soon, given the uptake in ev's starting to gather pace ?

orrery

EVandPV wrote: »

...
Someone mentioned ev battery life, I know of someone with a Zoe that's done 80k miles and the battery SOH is still at 100% ! That gives me encouragement enough to see a decent lifespan for a home battery.

That sounds beyond remarkable. I'd suggest that you're not seeing the real SOH. My Leaf still has 12 bars after its first year and 8k miles but I'd guarantee that the SOH isn't 100% behind the scenes.

My question is, is it worth holding off in the hope battery prices will fall ? Is it even likely they will fall anytime soon, given the uptake in ev's starting to gather pace ?

You'd need a crystal ball. There are about 20 giga-factories for batteries in the pipeline, with about 18 months from ground works to 1st production. The question is: will EV takeup still keep the prices high as supply comes on line. My guess it that there has to be a reduction simply because the power density is increasing.


The second question is: do you want to wait for the reduction before you buy and start to see the benefits. I'd guess from your actions thus far (well done, by the way) that you'll go ahead anyway.

EVandPV

orrery wrote: »

That sounds beyond remarkable. I'd suggest that you're not seeing the real SOH. My Leaf still has 12 bars after its first year and 8k miles but I'd guarantee that the SOH isn't 100% behind the scenes.

I had my doubts too at first but this was using an ODB2 reader with 3rd party software.
There's also reports of 10 year old Nissan Leafs still with over 90% SOH.

Must admit, I'm close to pulling the trigger on the Pylon batteries. £500 or so less and there wouldn't be as much hesitation.
As I say, it'll depend on getting the price for the batteries and inverter down a bit with some haggling.
I'm also not sure which inverter to got for.
The Sofar ME3000 seems to be the one most commonly supplied with the Pylons as a kit but doesn't have great monitoring or remote control.
Another budget option is a Solis 5G RAI which appears to have better monitoring/remote control but I can't find a great deal of info or reviews about it.
Can anyone recommend a sub £1000 ac coupled inverter ?

1961Nick

EVandPV wrote: »

I had my doubts too at first but this was using an ODB2 reader with 3rd party software.
There's also reports of 10 year old Nissan Leafs still with over 90% SOH.

Must admit, I'm close to pulling the trigger on the Pylon batteries. £500 or so less and there wouldn't be as much hesitation.
As I say, it'll depend on getting the price for the batteries and inverter down a bit with some haggling.
I'm also not sure which inverter to got for.
The Sofar ME3000 seems to be the one most commonly supplied with the Pylons as a kit but doesn't have great monitoring or remote control.
Another budget option is a Solis 5G RAI which appears to have better monitoring/remote control but I can't find a great deal of info or reviews about it.
Can anyone recommend a sub £1000 ac coupled inverter ?

The Sofar ME3000 has very good monitoring through the Solarman app, but zero remote control.

GreatApe

joefizz wrote: »

Quick update on the oil situation.
Just about to order home heating oil. Normally I would order in the region of 1100 litres the first week in September to completely fill the tank.
I'll be ordering now next week (first week in November delivery) and I dont think I could fit 900 litres in, possibly 800.

So thats hit the target using the battery to power ashp and immersion of reducing yearly oil consumption by at least 300 litres given the 2 month time shift plus less oil needed.

As of last night, heating is back on to winter settings so will run the ashp down.
Oil price is roughly the same as it was back at the start of September although it did spike inbetween so no real savings in monetary terms with the time shift. If its repeated next year then there could be an argument for the time shift causing the price to rise (start of Jan) so might be a case of buying lesser amounts during cheaper parts of the year (offset by bulk pricing savings etc).

300 odd litres saving only works out at about 140 quid this year so in monetary terms pushes the ashp recovery time out a bit but the discussion over on the BEV thread made me think about it in terms of CO2 and it works out at a bit less than half my yearly diesel driving amount in fuel which is something to think about.
Other than faffing about with a manual timed switch on the immersion and manually turning the ashp on theres been no real difference in lifestyle (same temperature, same level of hot water, if anything the immersion water is slightly hotter because its immediately used).

Last night it was -2C out near the ashp external unit so its really not feasible for here during winter.

Am tempted just to order 500 litres and see how it goes but its pretty much the lowest price its been in almost 2 years...

What's the reason for using the oil rather than continue using the ASHP?

If you have an EV you can get an electricity tariff of just 8p a unit for all weekend and weekdays 9pm to 7Am. 16p other times. That's roughly 60% of hours is 8p and 40% of hours is 16p

If you are getting 3 COP from your ASHP it would be 8p/3 = 2.7p per unit of heat which is probably cheaper than your oil. If you're paying 50p for oil that's roughly 5p per unit of energy say 90% efficient boiler = 5.5p per unit of heat. So the ASHP should be half the price of oil boiler

Even with a normal electricity tariff at 15p a unit the 3COP heat pump would be 10% cheaper than the oil.

You could also run the ASHP during the warmer days/nights or only during the period 11AM to 7pm when it's warmer outside so the COP is higher.


There is also a cheap 5p electric tariff from octopus energy during 12.30-4.30
If you are on that tariff the electricity is so cheap you can use resistance heaters and still save money relative to oil fired heating. At least for those 4h... And use the oil for other times.

EVandPV

1961Nick wrote: »

The Sofar ME3000 has very good monitoring through the Solarman app, but zero remote control.

Cheers, that's what I thought judging by the app.
Not a deal breaker as we'll have easy access to the inverter but remote control would be handy to have.
I guess once it's up and running as required, you won't need to touch it again for a while.

joefizz

GreatApe wrote: »

What's the reason for using the oil rather than continue using the ASHP?

Live in NI, north side of a mountain!

Outside temp last night -6C, borderline min operating conditions for my pump. Heater would have been used to stop external unit freezing so COP would have been about 1-1.5 not enough to heat a whole house at -6C outside.
Even at +5C (now my turn off temp) the COP drops to about 2ish so not enough to heat the house, even as well insulated as it is (although turning off fresh air ventilation did help)



Entire electric bill for the year comes in at around 100-120 quid. E7 standing charge would be about a third of that, so doesnt make economic sense either.


Not having a go but people forget that COPs are made up numbers and drop off with outside ambient temperatures. Also that u values are based on per degree temperature difference so 20C inside last week was a 10C temp difference, last night it was a 26C temperature difference. Even at midday today in the shaded part of the patio, the flagstones still had frost on them.

GreatApe

joefizz wrote: »

Live in NI, north side of a mountain!

Outside temp last night -6C, borderline min operating conditions for my pump. Heater would have been used to stop external unit freezing so COP would have been about 1-1.5 not enough to heat a whole house at -6C outside.
Even at +5C (now my turn off temp) the COP drops to about 2ish so not enough to heat the house, even as well insulated as it is (although turning off fresh air ventilation did help)

Entire electric bill for the year comes in at around 100-120 quid. E7 standing charge would be about a third of that, so doesnt make economic sense either.

Not having a go but people forget that COPs are made up numbers and drop off with outside ambient temperatures. Also that u values are based on per degree temperature difference so 20C inside last week was a 10C temp difference, last night it was a 26C temperature difference. Even at midday today in the shaded part of the patio, the flagstones still had frost on them.

Surely COP never is as low as 1 a simple resistance heater is 1

Can you get the octopus go tariff in NI?
At 5p/KWh you can heat the tank and use resistance heaters for 4h each day
The resistance heaters would be marginally cheaper than oil but significantly more green since the grid is 50% green 50% natural gas

How do you use the heating? On 24h a day?
If so you can perhaps convert 20% of your heating to resistance heaters and keep 80% as oil
Use residence heaters from 12.30-4.30 and oil from 5.30-midnight

When I stayed in a resistance heated house in Norway it was common to heat just the bedroom from say 11pm -7am then go to work then come back 7pm and heat the living room from 7pm to 11pm. This way you'd only heat one room while using that room rather than the whole house which is perhaps using only 1/5th as much electricity as heating the whole house. 3KW resistance heaters were really cheap and warms a room up quite rapidly

joefizz

GreatApe wrote: »

Surely COP never is as low as 1 a simple resistance heater is 1

Indeed. Think about it, not only do you need to run the ashp but you also need a heater/defrost on the outside module to stop it from freezing... at -6C thats pretty much on all the time. Add to that stupid planning laws which means the only place you can site it is on a north facing wall... -7C is min operating temp for mine, Id hazard a guess that at below that COP is less than one, or it just cant defrost the output side quick enough and COP goes to 0.
COP is a made up number to compare the electricity kwh in against the heat output compared to resistive. So if you are putting in 1kwh for the equivalent of 2kwh but using 1kwh to keep the frost off the outside unit thats a COP of 1.


Add to that the max operating thermostat internally. Scroll back a few pages and you will see a couple of us set IIRC 24-26C on the internal thermostat to get around 20C in the bedrooms or so at maybe 10-15C ambient. My internal thermostat only goes to 30C, so even with that going full pelt it might not be enough to offset differentials at those temperatures.
You could always not get a 500 quid cheap chinese unit and spend lots of dough but add in immersion hot water and the electricity bills go through the roof here.
Lots and lots of complaints here and in Scotland about new builds having ASHP heating only and the costs associated with it.

GreatApe wrote: »

Can you get the octopus go tariff in NI?

No. People have difficulty understanding its a different country... ask the prime minister(s) ;-)

GreatApe wrote: »

How do you use the heating? On 24h a day?

No. Enough to heat in the evening and then again at a point at the coldest. In full winter, on all the time, well the buttons on all the time, the heating cuts in and out as needed. Have went from about 1800 litres a year to 1100 and this year down to 800 with various measures and installing ashp/immersion on the battery during summer.

GreatApe wrote: »

When I stayed in a resistance heated house in Norway it was common to heat just the bedroom from say 11pm -7am then go to work then come back 7pm and heat the living room from 7pm to 11pm. This way you'd only heat one room while using that room rather than the whole house which is perhaps using only 1/5th as much electricity as heating the whole house. 3KW resistance heaters were really cheap and warms a room up quite rapidly

Ive now insulated the house as far as I can to norway standards but the walls cant be. I work from home, although the equipment losses do add to the heating.
Norwegian ashps work to a lower temperature although they do have the price to match.
Dont forget the norwegian grid is a hell of a lot greener and a hell of a lot cheaper even without the difference in wages.
I miss the heated bathroom floors in norwegian houses ;-) Thought about doing the resistance heated mat here when I redid the bathroom but would never really get the benefit and a few rugs thrown down was a lot cheaper!



The problem is that in certain places none of the theory works in reality.

To put it in perspective this house was built early 80s and had a coal fire and back boiler. Now that was a pita when the fire went out in winter...

Most heating here is oil with some gas in greater Belfast.

joefizz

EVandPV wrote: »

The Sofar ME3000 seems to be the one most commonly supplied with the Pylons as a kit but doesn't have great monitoring or remote control.

Just out of sheer noseyness, what would you want to remote control? grid charging capability?