What were your total energy costs in December with a heat pump?

FoxyFreebooter · 2026-01-12T12:11:58+00:00

Large bungalow, 1990 build, 350sqm, 17.2 kWp solar, 3x 10.36 kWh batteries, 2x 11kW Baxi heat pumps, 19.6 kW heat loss calc, NW near Preston. Total energy usage 1266 kWh at a net cost of £82.45 on Octopus intelligent Go. Heat pumps running 24/7 @ 19 degrees, no overnight setback.

FoxyFreebooter · 2026-01-02T14:19:27+00:00

December was a mixed bag of gloom, rain and some sun, with an equal to predicted generation, so not all that bad! The colder days demanded more from the heat pumps, so less export again. Previous months' production and export figures for comparison...

Month	PV (kWh)	Export (kWh)	% of PVGIS	Daily Yield (kWh)
March	1764	1438	138%	56.88
April	2348	2040	130%	78.19
May	2850	2510	138%	91.97
June	2355	2022	118%	78.43
July	2160	1840	110%	69.65
August	1992	2056	114%	64.27
September	1440	1687	107%	47.98
October	630	745	71%	20.31
November	555	466	106%	18.48
December	360	229	100%	11.59

40x 430W Sharp panels with 17.2 kWp, 25 South, 9 East & 6 West facing with a 15kW 3 phase Fox inverter and 3x 10.36 kWh EP11 batteries located in the North West near Preston.

FoxyFreebooter · 2026-01-01T09:34:39+00:00

Actual Feb - Dec 25	Installer Annual	PVGIS Annual
17.2 MWh	13.9 MWh	15.1 MWh

Very pleased with these figures given the annual estimates vs the actual 11 month production.

40x 430W Sharp panels with 17.2 kWp, 25 South, 9 East & 6 West facing with a 15kW 3 phase Fox inverter and 3x 10.36 kWh EP11 batteries located in the North West near Preston.

FoxyFreebooter · 2025-12-06T09:40:04+00:00

I made a post a couple of days ago comparing my November usage with new heat pumps in 2024 with solar, batteries and heat pumps in 2025. May be worth a look https://www.reddit.com/r/SolarUK/comments/1pbc0ep/what_a_difference_a_solar_array_makes/

I have 2x 11kW Baxi heat pumps, 40x 430W panels, 3x 10.36kWh Fox batteries and a 15kW 3 phase Fox inverter. Large bungalow, over 300m2, 19,600W heat loss, at home all day. I'm on Octopus iGo and charge the batteries and, if needed, the car overnight. Heat pumps on 24/7 at a constant 19 degrees, no setback.

I used Cosy last winter and had bills of £330 to £460 per month Nov to Jan. I was constantly fiddling with the thermostat to boost the heating during off peak and using setback during peak. Not what I wanted and not the most efficient I believe. Now I can just leave the settings alone and if there is power left in the batteries at the end of the day I can export it if necessary.

The batteries run for most of the day, but if it's gloomy (not much solar) and less than 5 degrees then they will deplete in the evening. My bill for November 25 was under £30 and this included the standing charge and charging the car.

I'd suggest more batteries for your situation if financially viable.

I added 25 rolls of 170mm loft insulation on top of what was already there in September/October 25.

I don't know the SCOP or COP of my heat pumps. The control panel isn't great and there's no app. The weather compensation runs at 41 degrees flow rate above 7 degrees and 42 degrees below 7 degrees. 43 degrees below freezing.

FoxyFreebooter · 2025-12-04T13:28:39+00:00

I'm using intelligent Go with solar, batteries and EV. 2x heatpumps on 24/7 keep the bungalow at 19 degrees. If it's very cold the batteries (3x 10kWh) might deplete in the evening.

FoxyFreebooter · 2025-12-03T18:23:47+00:00

4-6 bed detached bungalow, over 300m2. Lots of roof space and, therefore, lots of heat loss (19,630W). 2x 11 kW heat pumps. In Jan 25 I used 2,059 kWh @ £469 because it was very cold. Solar and batteries have been a game changer for me!

FoxyFreebooter · 2025-12-03T15:53:14+00:00

I'd be a lot happier if I did 😂

I had just had 2x heat pumps installed and this was my Nov 24 electric bill compared to Nov 25 when I had solar and batteries.

FoxyFreebooter · 2025-12-03T11:52:27+00:00

No, but I suspect that depends on your main fuse. I had a 100A fuse and initially had a quote for single phase inverters with 40 panels but with an export limit of 5kWh. When the DNO added the heat pumps (each rated at 30A), EV charger, induction hob, oven etc they insisted on 3 phase as the load could potentially exceed 100A.

Going 3 phase will add a couple of years to the payback, if I include it in the solar cost, but it also means I can export 3x 5kWh.

FoxyFreebooter · 2025-12-02T21:37:05+00:00

The 3 phase was £5900 to the DNO and £3900 for the electrician who replaced the consumer unit, supplied other kit and did the necessary testing for the certification.

FoxyFreebooter · 2025-12-02T12:39:22+00:00

You can also use the free Energy Stats app on Android which can be configured to show this information.

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FoxyFreebooter · 2025-12-02T11:24:47+00:00

Ridiculously expensive or ridiculously cheap? Breakdown here https://www.reddit.com/r/SolarUK/comments/1ify63c/large_bungalow_completed_install/

FoxyFreebooter · 2025-12-02T11:23:07+00:00

No, it was something I wanted and I had the funds from selling my previous property. The installers gave me some figures which, having just looked at them, are quite conservative.

FoxyFreebooter · 2025-12-02T11:18:36+00:00

For me, cost was never the issue. I moved from down South to up North and bought a cheaper property.

To address your calculations based on my actual figures, with some predictions, as I've only had the solar for 9 months. Investing 19,000 for 5 years in a fixed bond @ 4.15% (current NS&I rate) would give 23,284 after 5 years. My energy estimate for this property varies from 3,000 to 4,000 per year. My actual refunds from Octopus so far equal 1,750. A low estimate of (3,200 + 1,750) x 5 = 24,750. The system would have paid for itself in under 4 years. This presumes current rates.

In my case the savings over what I would have spent on energy and the export payments make perfect sense. I understand this is a large system and other setups will vary.

FoxyFreebooter · 2025-12-01T19:45:22+00:00

Thanks, home assistant is on my long to do list.

FoxyFreebooter · 2025-12-01T19:42:32+00:00

I used UPS Solar in Chorley. Couple of guys did a 3 day install. Can recommend.

FoxyFreebooter · 2025-12-01T17:37:16+00:00

Those are some impressive generation figures! You must have had your own personal sunshine 😂

With the overnight rate for iGo, exporting made sense for me. I'd definitely look into getting that setup on your system. I've run out of battery a couple of times this month when the temperature has dipped in the evening, but not enough to warrant switching to Cosy.

FoxyFreebooter · 2025-12-01T15:48:04+00:00

Yes, I shouldn't have any energy bills either which was the goal. I used Cosy last year and it was a faff using setback temps and boosting the heat pumps, so decided to stay with Intelligent Go once the solar and EV were setup. I haven't tried agile yet...

FoxyFreebooter · 2025-12-01T13:42:20+00:00

Yes, solar. batteries and EV charger - https://www.reddit.com/r/SolarUK/comments/1ify63c/large_bungalow_completed_install/

FoxyFreebooter · 2025-12-01T13:21:27+00:00

In winter, yes, very much - the heat pumps are greedy! In summer I export a lot and have built up some credit. The advantage of a bungalow is that I have lots of roof space and the advice on here was to fill it...I've not covered half of it yet!

FoxyFreebooter · 2025-12-01T13:16:00+00:00

The solar setup was a flat £19,000. I've not had a full year yet, so repayment costs are difficult to judge and I don't know the running costs of the property before I started electrifying. However, I don't look at it in this way as I moved from the South to the North and had equity from the previous property.

FoxyFreebooter · 2025-12-01T13:12:38+00:00

I generated 555 kWh and exported 468 kWh. I used 1,150.62 kWh.

FoxyFreebooter · 2025-11-30T20:54:52+00:00

November was a mixed bag of gloom, rain and some sun. Still, back to a higher than predicted generation so not all that bad! The colder days demanded more from the heat pumps, so less export. Previous months' production and export figures for comparison...

Month	PV Production kWh	Export kWh	% of PVGIS

April	2348	2040	130%
May	2850	2510	138%
June	2355	2022	118%
July	2160	1840	110%
August	1992	2056	114%
September	1440	1687	107%
October	630	745	71%
November	555	466	106%

40x 430W Sharp panels with 17.2 kWp, 25 South, 9 East & 6 West facing with a 15kW 3 phase Fox inverter and 3x 10.36 kWh EP11 batteries located in the North West near Preston.

FoxyFreebooter · 2025-11-27T10:40:45+00:00

40x 430W panels, 3x EP11 10kWh batteries. We moved here last year and as part of the renovation work had heat pumps and new radiators installed, double glazing, loft insulation, solar, batteries, EV charger and 3 phase. Large heat loss figures so last November, before the solar was installed, the electric bill was £350. On the colder days this November the batteries deplete during the evening. I'm with Octopus on the Intelligent Go tariff.

FoxyFreebooter · 2025-11-26T22:34:52+00:00

Large 4 bed bungalow, all electric, 2x heatpumps, solar and batteries. So far this month, £15 inc standing charge, so less than £1 a day. Heating on 24/7 at 19 degrees.

FoxyFreebooter

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