Choice of intelligent switches ?

danesol

Just for the record, I agree on the amount you can possibly save, but the revenue cant all come from the energy divert !

zeupater

danesol wrote: »

Just for the record, I agree on the amount you can possibly save, but the revenue cant all come from the energy divert !

Hi

Looks like you've just realised that £8/month multiplied by 12months comes to £96 ... not a million miles away from M's £100 ...

Anyway, I'd reckon that diverting 2000kWh/year would be pretty much impossible for most to achieve. The excess generation in summer would be more than necessary to heat the average household's water whilst in winter there simply isn't enough generation to support base load and heat water ... the BRE SAP calculation would suggest that an average family home would benefit from ~1100kWh.t/year of solar heating, and that's based on usage patterns with a correctly sized source. Oversizing the collector capacity adds nothing significant to the SAP calculated usage ...

We have the ability to meter our solar thermal heat provision and have ample hot water stored in an oversized cylinder so as to provide a buffer for dull periods, yet fall well short of 2MWh.t of provision .... I'd reckon that it would be very rare (but not impossible for a supplier ... ) to find a household with a typical domestic pv array, typical storage capacity and typical HW usage which would divert ~2MWh ....

HTH
Z

danesol

zeupater wrote: »

Hi

Looks like you've just realised that £8/month multiplied by 12months comes to £96 ... not a million miles away from M's £100 ...

Anyway, I'd reckon that diverting 2000kWh/year would be pretty much impossible for most to achieve. The excess generation in summer would be more than necessary to heat the average household's water whilst in winter there simply isn't enough generation to support base load and heat water ... the BRE SAP calculation would suggest that an average family home would benefit from ~1100kWh.t/year of solar heating, and that's based on usage patterns with a correctly sized source. Oversizing the collector capacity adds nothing significant to the SAP calculated usage ...

We have the ability to meter our solar thermal heat provision and have ample hot water stored in an oversized cylinder so as to provide a buffer for dull periods, yet fall well short of 2MWh.t of provision .... I'd reckon that it would be very rare (but not impossible for a supplier ... ) to find a household with a typical domestic pv array, typical storage capacity and typical HW usage which would divert ~2MWh ....

HTH
Z

That was an estimation based on how much it actually cost to heat water using GAS energy and I believe I save more !

However his calculations ( assumptions ) are wrong, as he's using the amount of energy used by GAS to heat water, NOT electric, but his final answer luckily for him is more or less correct for some...... but that doesnt the workings out right ! LOL

Remember 2mwh of ELECTRICAL energy isnt exactly the same in GAS terms when discussing or making calculations concerning a heating source, and what I mean by this is that to make a proper comparison, you need to know how many kwhs of energy is required to heat a full tank using GAS and then the same with Electric - it is NOT the same figure !

legoman62

danesol wrote: »

But i've come from the other angle and worked out how much it costs to heat the water using GAS and therefore what you actually SAVE when you switch your GAS completely OFF which we have done for the past quarter, the calculations although different give more or less the same resultant answer.

My gas has been "Off" for the last quarter too, but Eon's standing charge is screwing me! I've looked at providers with no standing charges but, the costs are much the same:D

danesol

legoman62 wrote: »

My gas has been "Off" for the last quarter too, but Eon's standing charge is screwing me! I've looked at providers with no standing charges but, the costs are much the same:D

LOL, at actually looked at that myself, so to see if next time it would make sense to get a provider with NO standing charge, but its difficult to workout accurately your potential saving without 12mths history which I havent got yet and dont want to assume....

But you highlight a very valid point which I will be looking closing at next year when I have both 12mths readings and come to an end of my current EDF fix term.

Martyn1981

danesol wrote: »

That was an estimation based on how much it actually cost to heat water using GAS energy and I believe I save more !

Never said you didn't! In fact if you look at my post again, I was suggesting a minimum saving figure - for 2MWh of divert.

If you look back, you'll see that I suggested 1MWh of leccy divert could equate to £90 depending on tariffs.

Martyn1981 wrote: »

Winter months 250 / 75% efficiency * 3.948p = £13.16
Summer months 750 / 75% * 7.642p = £76.42
Total = £89.58

danesol wrote: »

However his calculations ( assumptions ) are wrong, as he's using the amount of energy used by GAS to heat water, NOT electric, but his final answer luckily for him is more or less correct for some...... but that doesnt the workings out right ! LOL

No idea what you are on about here! I referred to 2MWh of leccy divert, and converted that to 2.5MWh of gas via the suggested 80% efficiency. I'm surprised that you are still saying this is wrong when Zeup has already explained it to you!

danesol wrote: »

Remember 2mwh of ELECTRICAL energy isnt exactly the same in GAS terms when discussing or making calculations concerning a heating source, and what I mean by this is that to make a proper comparison, you need to know how many kwhs of energy is required to heat a full tank using GAS and then the same with Electric - it is NOT the same figure !

Once again ... hence the 80% figure to give a quick conversion!

It seems that having accused me of being wrong, you are now trying to dig your way out of a hole by pointing out what I failed to include DESPITE it being included in the first place.

I could be cruel and add lots of LOL's back, but I can't be bothered.

Mart.

Martyn1981

zeupater wrote: »

We have the ability to meter our solar thermal heat provision and have ample hot water stored in an oversized cylinder so as to provide a buffer for dull periods, yet fall well short of 2MWh.t of provision .... I'd reckon that it would be very rare (but not impossible for a supplier ... ) to find a household with a typical domestic pv array, typical storage capacity and typical HW usage which would divert ~2MWh ....

HTH
Z

Hiya Zeup, I also reckon 2MWh is the upper end, but I was prompted to ask 'just ask', after reading a 1 yr review:

August 2012 to July 2013

3.92kwp pv

Produced 3708

Used 1573 42.42%

through immersun 1955 52.72%

to grid 180 4.8%

Power only went to grid when either the thermal store was up to 70 deg c or the panels were producing more than the house load plus the immersion element.

Don't shoot the messenger, but starting to wish I hadn't bothered now.

Mart.

Zeup, addendum. Just checking info and note that the poster has a 300lt thermal store. Am I right to assume this would make a big difference to the amount that could be diverted in the BST months? M.

zeupater

Martyn1981 wrote: »

...Zeup, addendum. Just checking info and note that the poster has a 300lt thermal store. Am I right to assume this would make a big difference to the amount that could be diverted in the BST months? M.

Hi

That makes a huge difference by providing the buffer which I mentioned in an earlier post .... you'd probably find that 300litres at an initial temperature of 70C, combined with a TMV would buffer against something like 3 to 5 days (or more, depending on usage) of pretty dull skies .... this is why the complete solution needs to be considered, not just the collectors. A couple of consecutive dull days, which is very common, with a standard 117litre cylinder means that you'll need the immersion/boiler fired up ... store three times the volume and you're moving into a period of consecutive dull days which is rare ...

Our target storage temperature for solar thermal is a little higher than 70C, with the GCH backup set to heat/stratify the upper section of the cylinder to ~50C if the top thermostat temperature is still too low in the evening (it's on manual at the moment though !), so we both increase the buffer capacity and minimise the GCH input when required.

HTH
Z

zeupater

danesol wrote: »

LOL, at actually looked at that myself, so to see if next time it would make sense to get a provider with NO standing charge, but its difficult to workout accurately your potential saving without 12mths history which I havent got yet and dont want to assume....

But you highlight a very valid point which I will be looking closing at next year when I have both 12mths readings and come to an end of my current EDF fix term.

Hi

It's pretty straightforward for us .... we're on a NSC contract at the moment and pay absolutely nothing for gas for two quarters/year, the saving is therefore the displaced imported energy cost + the standing charge.

You'll find that the Government's/Ofgem's requirement for the suppliers to simplify the energy market because we, the consumers, are considered to be 'thick' will simply cripple the anticipated savings for low energy consumer/renewables users - and, of course, that's why the suppliers decided to simplify towards SC instead of NSC, pulling a 'quick one' past Ofgem without them realising it (yet! - why, oh why, do we employ such dim-witted morons to act as regulators ). Tiered NSC supply is simply following in the footsteps of the dinosaurs, however, there is still the option of a single tariff NSC .... but you'll need to move away from the 'Big 6' suppliers ...

HTH
Z

sly_dog_jonah

Martyn1981 wrote: »

Hiya SDJ, just wondering how the first year has gone. Do you know how many kWh's you managed to divert?

Also wonder if anyone on here has managed to divert around 2MWh's which would roughly equate with the suggested/hoped for target of £100 savings (against gas assuming approx 4p and 80% efficient (more with tier 1 savings)).

Mart.

Hi Mart,

1275kWh diverted to date since installation 20/9/12. Will post some detailed stats after the anniversary.