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Recent leccy bill

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811 kWhs
Joined: 5 months ago
Posts: 129
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There are a couple of topics already floating about around sharing bills, so @editor it may be necessary to do a bit of combining and tidying; I fully understand this particular post may well end up within another thread.

However, in the spirit of sharing experiences I thought it best to give an update on our cost of living with an ASHP hitched up to a battery and solar PV setup. In particular, we finally managed to get an export tariff set up with Octopus in early March and we've now had a couple of months of good solid data to see how everything is now hanging together.

Since 6th March, we've imported 1024 kWh from the grid, averaging 16kWh per day. We've also used 386 kWh of our own home-generated leccy (6 kWh per day) meaning an overall average of 22.05 kWh per day consumed. Breaking this out, the ASHP has been responsible for 12kWh per day and everything else 10 kWh per day. On the other hand, we've exported 867 kWh, averaging 13.5 kWh per day.

Now we've had our bills in from Octopus, the imports and exports are offset by a couple of days, but approximately speaking it cost us £265 to buy in the imported leccy and we were paid £147 for our exports. Net result, about £117 for the whole period (averaging £1.84 per day). Incidentally, since I know our rebates and I know the daily kWh figures, I've calculated that to be an average of about 16.5p per unit that we've been getting paid for our exports back to the grid. If ever anyone needed evidence that a flexible export tariff is outperforming the 7.5p per unit fixed rate, there it is. Yes, I am well aware the flexible tariff figures could easily fall, but I can still change tariffs if that lasts for any significant time.

To reiterate context, I'm well aware May is one of the sunniest months and indeed we hit our record yesterday (32 kWh generated, of which 28.71 exported), so these figures cannot be simply extrapolated over the whole year. Also, despite the fact we can easily argue the cost of the solar PV and battery has increased the value of the house by at least as much, that's only a paper exercise; the ASHP was a cost of £4,000 and the solar stuff another £7,500. We'll have to see quite a few of these reduced bills before we start talking seriously about return on investment in pure financial terms.

Also, to reiterate context, our previous heating and DHW bills came from oil which has risen (since we had the ASHP installed) from 61ppl to 98.5ppl. That equates to a change in annual cost from £1,300 to £2,100 approximately (an increase of about £800 per year). That rise has definitely done more to justify the cost of the ASHP and solar PV.

Other potentially useful stats are the maximums and minimums since 6th March:

  • Our best daily export was 28.71 kWh
  • The maximum we consumed from the grid in a day was 31.73 kWh. The minimum was 6.375.
  • The maximum we've generated in one day from the solar PV was 32 kWh. The minimum is 2.6. Well worth noting that yes that does mean we've never had a day where we haven't generated at least something.
  • On its greediest day, the ASHP has consumed 29.3 kWh for a combination of hot water and heating. On its best day, it consumed just 3 kWh.
  • Our electrical consumption for everything not ASHP related has varied from 15.54 kWh to just 2.12 in a day.
  • Our consumption tariff in early March was about 22p peak and 15p overnight. It is now 32p/21p after the increase in price cap.

Finally, I will say that getting our DNO (UK Power Networks) to actually provide Octopus with an export MPAN so we could start exporting was like hitting the tail of a dinosaur. It took a long time to find someone who could help, but when we found her she was excellent. In contrast, dealing with Octopus to get their part sorted was quick and easy throughout. I'm sure I'd have lost the will to live if I'd had to deal with two different webs of bureaucracy but dealing with at least one efficient and effective support function was invaluable.

Make what you will out of all that.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and inverter
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solim profundum variat"

Mars and Kev M liked


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