Immersion Diversion - Do you turn off your boiler in summer?

MonsieurFrugal

Yes - although it's still timed to come on in the mornings but the thermostat on the HW tank stops it if the tank is already warm enough 99% the time the solar keeps it hot. We use all the tanks water every morning when bathing etc

In 16 months the diverter has diverted 1637kwh into the immersion about £230~s worth

I paid £165 for it from my local wholesaler and fitted it myself (I am an electrical engineer)

defaultdriver

Hi,
We switch the boiler on only when needed. The past two weeks have been good as we have hardly used the boiler. I think we have had at most 4 days when we have not had the boiler on at all. Normally we do not get enough hot water for a bath/shower till after 11.30am. Went over 1000kWh since install in July.
defaultdriver

Cardew

MonsieurFrugal wrote: »

In 16 months the diverter has diverted 1637kwh into the immersion about £230~s worth

Do you really pay 14p per kWh for electricity?

Assuming you have gas, wouldn't it be fairer to cost the savings at the price of gas - taking into account boiler efficiency for water heating?

Sterlingtimes

In a four adult household, we used 502 kWh of gas during July at a price of £21.19. Solar diversion to the immersion amounting to 75 kWh avoided 150 kWh of addition gas usage. Financial saving was zero given that we lost metered export revenue owing to the diversion. At current gas prices the Solar iBoost serves no effective purpose.

defaultdriver

Cardew wrote: »

Do you really pay 14p per kWh for electricity?

Assuming you have gas, wouldn't it be fairer to cost the savings at the price of gas - taking into account boiler efficiency for water heating?

Hi,
What would you say is the accepted method of calculating the savings ? Am interested, as I would like to do this calculation at end of first year.
Thanks
defaultdriver

defaultdriver

Sterlingtimes wrote: »

In a four adult household, we used 502 kWh of gas during July at a price of £21.19. Solar diversion to the immersion amounting to 75 kWh avoided 150 kWh of addition gas usage. Financial saving was zero given that we lost metered export revenue owing to the diversion. At current gas prices the Solar iBoost serves no effective purpose.

Hi,
Does this mean that you are not on deemed 50% export? I do agree that if not on deemed export the diversion would likely not save any money.
Thnx
defaultdriver

Cardew

defaultdriver wrote: »

Hi,
What would you say is the accepted method of calculating the savings ? Am interested, as I would like to do this calculation at end of first year.
Thanks
defaultdriver

IMO you should take the total amount of kWh diverted and multiply it by the cost you pay for a kWh of gas. You then have to take into account the efficiency of your boiler in producing hot water.

You need to bear in mind that all boilers, even new boilers with a hypothetical 90+% efficiency, have much lower efficiency for Hot water. Sterlingtimes above uses a figure of 50% which is a good 'ballpark figure'.

So if you pay 3p/kWh for gas and divert, say, 1000kWh to your HW tank your savings would be £60.

Sterlingtimes

defaultdriver wrote: »

Hi,
Does this mean that you are not on deemed 50% export? I do agree that if not on deemed export the diversion would likely not save any money.
Thnx
defaultdriver

Those of us with a smart meter which measures export lose "deemed export" status and are paid for actual export.

Sterlingtimes

defaultdriver wrote: »

Hi,
Does this mean that you are not on deemed 50% export? I do agree that if not on deemed export the diversion would likely not save any money.
Thnx
defaultdriver

Price of export 4.91 p per kWh
Price of gas including VAT at 50% efficiency 4.88 p per kWh

Figures are too close to determine whether to burn gas or divert solar.

defaultdriver

Sterlingtimes wrote: »

Price of export 4.91 p per kWh
Price of gas including VAT at 50% efficiency 4.88 p per kWh

Figures are too close to determine whether to burn gas or divert solar.

We do not have a smart meter at the moment, will put this off for as long as possible
and hopefully get at least the cost of the iBoost back before we might be forced to upgrade