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What a year of solar and batteries saved us in 2025

scotthelme.co.uk

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Re: What a year of solar and batteries saved us in 2025

#71

Post by aniviacat »

ozlikethewizard wrote: post #63
pjc50 wrote: post #54

Earlier quoted context omitted.

UK considerations: must be at least signed off by an approved electrician ("Part P" regulations), and for any situations involving subsidy needs to be MCS approved as well. https://mcscertified.com/

Surely it only needs to be signed off if you intend to sell the property with them or sell excess back to the grid. If youre just using the batteries how is anyone going to know?

I'd assume your fire insurance covers nothing if illegally installed batteries are found inside after a house fire.

Re: What a year of solar and batteries saved us in 2025

#72

Post by subroutine »

rokkamokka wrote: post #31
lm28469 wrote: post #27

Earlier quoted context omitted.

It's high but it really depends on your lifestyle and appliances. If you have a heat pump water heater and heat pump based floor heating you'll use 1/4th of the energy as the same house with resistive water/floor heating. A house which barely passed regulation from 2010 will consume 5-10x the energy of a certified passive house. etc. That being said I think you have to draw the line somewhere. I'd much rather have in…

Heatpumps are not a gimmick - they're an excellent technology with lots of efficient and effective uses :)

Heatpumps, Shmeetpumps

Re: What a year of solar and batteries saved us in 2025

#73

Post by UltraSane »

lm28469 wrote: post #44
BeetleB wrote: post #42

Earlier quoted context omitted.

Who spends $50K on heat pumps? They're not anywhere near that expensive.

I'm talking about geothermal water/water installs for central heating. No one is heating their place with air/air heat pumps besides americans who haven't figured out that heating spaces via air is shit tier in term of comfort and efficiency

says the guy calling heat pumps "voodoo appliances"

Re: What a year of solar and batteries saved us in 2025

#74

Post by latchkey »

toomuchtodo wrote: post #55
mbesto wrote: post #52

It's wild how overpriced Tesla Powerwalls are. 16 kWh battery with all of the UL supported listings etc = $3300 [0] 13.5 kWh Tesla Powerwall is $12k~$15k You would get your return way back quicker. [0] - https://www.ruixubattery.com/product-page/lithi2-16-battery-... EDIT: As others have pointed out, powerwalls have inverters built in so it's not totally apples to apples. You can get a beefy inverter for $5k and it's…

They have a 30% gross margin, they're just soaking up the federal US tax credit (which is also 30% for battery storage and extends through 2032). Alternatives: https://electrek.co/2025/12/28/opinion-its-time-to-start-rec...

A few of the alternatives have been reviewed by Will Prowse as well. His YT is a treasure of information. https://www.youtube.com/@WillProwse

Re: What a year of solar and batteries saved us in 2025

#75

Post by lm28469 »

Retric wrote: post #65
lm28469 wrote: post #44

Earlier quoted context omitted.

I'm talking about geothermal water/water installs for central heating. No one is heating their place with air/air heat pumps besides americans who haven't figured out that heating spaces via air is shit tier in term of comfort and efficiency

Having one place to handle humidity, temperature, and exchange of fresh air makes ductwork the king of comfort and efficiency.

Separation of concerns is the king of avoiding pricy maintenance and headaches.

You can already do most of that with a passive heat recovery ventilation system coupled to a ground/water exchanger. All systems are independent and the most high tech equipments you need are fans and a water pump

Re: What a year of solar and batteries saved us in 2025

#76

Post by jstsch »

j2kun wrote: post #28
jstsch wrote: post #12

Battery prices are getting really low, if you're willing to do some DIY. Just received a 15kWh battery from China. A 'Humsienk'. Combined it with a GroWatt SPA3000TL-BL inverter. Total price, 1600 euros. So close to the magical 100 euros per kWh. Driving it with some interesting combinations of Raspberry PI's and serial interfaces and custom written Go code, but it works... :)

I do wish I could have a good, in-depth tutorial on how to set this up myself. Along with (pipe dream) an explanation of how it would interact with my local utility. I worry that due to some silly technicality, I won't be able to export to my local utility, or else I won't be able to run off-grid when there's an outage.

I will do a write-up in a couple of days. It's all relatively simple, you just have to expect terrible documentation and do a bit of reverse engineering and serial sniffing. I expected the battery to be complicated, but it turned out that the inverter was.

You'll encounter stuff like: manual says use RS485 port on Battery for GroWatt inverter → need to use CAN port on Battery. Meter Port (RS485 [serial] over RJ45) wiring on GroWatt is unknown (A: white orange / B: white blue, cross them over). Dinky RS485 serial → USB converter needs a 120ohm resistor between pins for line termination. Growatt meter port expects a SDM630 meter, not a DTSU666 (hardcoded), so vibe code another emulator. DIP switches for RS232 connection need to be both on the ON position (undocumented). CH340 USB→serial converter for RS232 does not work, but one with a Prolific chip does. Etc. etc. etc :)

Oh, and the biggest one... I was expecting to be able to just send a command, 'charge at 500watts', now... 'discharge at 2000watts'. But no. You have to emulate a power meter and the inverter will try to bring the net power to 0. Fun! :)

Re: What a year of solar and batteries saved us in 2025

#77

Post by icegreentea2 »

elAhmo wrote: post #25

Great read! I am just wondering would stacking up batteries, charging them off-peak and using/selling back during peak usage be as good as this, or even better? Seems like this shouldn't be a viable scenario, but given the prices and idle capacity, it seems just investing in batteries and charging them at night, to be used/sold to the grid during the day would be as good as a solar installation.

The author pays £0.07/kWh off peak, but can export at £0.15/kWh. The author paid ~£7500 per powerwall which has ~13.5kWh capacity. Assuming full charge/discharge every night, you can make ~£1.08 per day, which works out to about 19 years to pay back.

Utilities normally consider disincentivizing this type of behavior from residential customers as one of the factors when setting their export pricing.

Re: What a year of solar and batteries saved us in 2025

#78

Post by youngtaff »

kccqzy wrote: post #2

Good analysis. And kudos to the author for saving money. But still 21.6MWh per year excluding solar production seems too high for a household. I use electric heating and drive an electric vehicle, and my household annual energy consumption is about one fifth of that.

I think Scott's usage is high – I think he mentions between £300-400 / month – but then he's got a hot tub, server rack as well as the cars.

We still have an ICE car and gas central heating but our combined electricity and gas bill is around £140 / month

Plan to go to EV and heat pump in our next house though

Re: What a year of solar and batteries saved us in 2025

#79

Post by baq »

ozlikethewizard wrote: post #63
pjc50 wrote: post #54

Earlier quoted context omitted.

UK considerations: must be at least signed off by an approved electrician ("Part P" regulations), and for any situations involving subsidy needs to be MCS approved as well. https://mcscertified.com/

Surely it only needs to be signed off if you intend to sell the property with them or sell excess back to the grid. If youre just using the batteries how is anyone going to know?

If your house burns down for any reason, not necessarily the DYI batteries, the insurance company will know anyway.

Re: What a year of solar and batteries saved us in 2025

#80

Post by lm28469 »

UltraSane wrote: post #69
lm28469 wrote: post #43

Earlier quoted context omitted.

Overly complex and fragile in the long run, the savings are meaningless if you're already self sufficient. I'd much rather spend the money in insulation and self sufficiency than these voodoo appliances. That's my reasoning my new build house with plenty of land. In other scenarios it might be more beneficial to go for them.

Heat pumps are no more fragile than air conditioners.

Yes, and that's why I have none.
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