http://www.car4play.com/forum Car4play forum en-gb Tue, 29 Sep 2026 14:22:33 +0100 Copyright: Car4play webmaster@car4play.com (Technical) 5 car4play692173 Tue, 29 Sep 2026 14:22:33 +0100 My house would run happily on 20kWh/day in the depths of winter with a heat pump, so being able to steal it from the car battery would be fine. Whether or not sifting off the top 30% of the battery on a daily basis would have an impact on longevity, I don't know. Adding batteries would be the first thing I'd do if I moved house. Solar can wait, the time of use tariffs mean you can get everything for 6-8p/kWh if you plan ahead. http://www.car4play.com/forum/post/index.htm?m=692173&v=e car4play692099 Thu, 24 Sep 2026 14:12:26 +0100 >> What does he do when he wants to drive somewhere and the car's empty because >> it's been running the house? >> >> Never quite worked out that conundrum myself. A large Kia EV9 has a 100kwh battery and a range of ~300 miles. Seems likely that a limit can be set on maximum discharge depending on your travel plans for the following day. Just doing school run and short commute - keep 100 miles range in the battery. Long journey planned - leave 80%+ charged. Plans can sometimes change at short notice. Worst case - top up with fast charge. Bit like petrol really - top up the "tank" if needeed. http://www.car4play.com/forum/post/index.htm?m=692099&v=e car4play692098 Thu, 24 Sep 2026 13:52:06 +0100 >> I know someone with one of those big Kia electric vehicles. He charges it overnight >> on cheap tariffs and runs the house from the car during the day. Would seem >> to alleviate having 2 sets of batteries. >> What does he do when he wants to drive somewhere and the car's empty because it's been running the house? Never quite worked out that conundrum myself. http://www.car4play.com/forum/post/index.htm?m=692098&v=e car4play692094 Wed, 23 Sep 2026 18:00:48 +0100 Vehicle to grid charging is in its early days. Cars that can do this are limited and the hardware required to support it all can be costly. Longer term this may be a very sensible way to go. I would wait a couple of years when it may become a better sorted proposition. Just buying batteries - some things to be aware of: Is energy usage fairly even or variable - eg: more consumption in winter. Batteries etc may need to be sized to meet maximum not average demand. Difference between day and night rates. Current price cap is 26p kwh. Night rates vary depending on supplier between 8-15p. So a saving of between 11-18p kwh. Assuming 3000kwh pa and a saving of (say) 15p kwh generates £450. Whether the price difference lasts over the next 10-15 years is crystal ball stuff. Personal view - it will shrink as EV sales increase and more folk use night time rates. Cost of 10kwh system - batteries + inverter + installation - quick Google shows £6-8k. Payback will be ~15 years. Superficially better deals - understand quality and longevity compromises. Finally - you need decent professional input - there are limits on the maximum continuous draw on batteries and inverter. Could be an issue if you have an instantaneous shower drawing lots of power, run domestic appiances simulateously. http://www.car4play.com/forum/post/index.htm?m=692094&v=e car4play692093 Wed, 23 Sep 2026 17:06:37 +0100 I believe you need a special inverter for that which last time I looked were upwards of £10k. (Also I had a feeling they weren't yet approved for UK but I expect I'm well out of date on that) I can do a small amount from mine - I think up to 2kWh, not even a kettle. Next door runs his garage from his, which is I think a chest freezer a fridge and lighting. http://www.car4play.com/forum/post/index.htm?m=692093&v=e car4play692092 Wed, 23 Sep 2026 16:56:52 +0100 I know someone with one of those big Kia electric vehicles. He charges it overnight on cheap tariffs and runs the house from the car during the day. Would seem to alleviate having 2 sets of batteries. http://www.car4play.com/forum/post/index.htm?m=692092&v=e car4play692087 Wed, 23 Sep 2026 14:11:39 +0100 Our local council recently has teamed up with a company to "do us a deal" on renewable energy, supposedly offering keen pricing on solar, heat pumps and batteries. Given I already have solar and I have inadequate space for a heat pump I just enquired about the batteries. I couldn't make it work in under about 10 years IIRC, and that assumes prices stay where they are (or get worse) and that the cheap overnight tariff differentials don't get eroded. FWIW I paid for about 4800 kWh in the last 12 months, higher than yours I expect because of EV charging. My elec bill for that was £795 incl VAT (which is about 16.5p per kWh, plus about maybe £220 standing charge!) so I'd be hard pushed to make a £600 pa saving!! (Plus I get a modest amount from the panels). Apart from the initial outlay, on a cost basis changing to an EV really is a no brainer and in my opinion would be a better use of your spare money than batteries, with a cheap overnight tariff. You don't need a new one car, there is a strong 2nd hand market with good prices on some cars. http://www.car4play.com/forum/post/index.htm?m=692087&v=e car4play692083 Wed, 23 Sep 2026 12:44:02 +0100 Anyone done this? My back of a fag packet calculations are thinking a 10kw battery, charge it up overnight on cheap rates then run the house during the day, would recoup capital costs a lot quicker than solar would ( especially in Scotland). I am approx 3000kw a year. A 20p per kw difference would be £600 a year saving. Even better if also charging an EV overnight as well. A quick google suggests prices from £1500 to about £5k so yet again, b***** confusing! Anyone done this? http://www.car4play.com/forum/post/index.htm?m=692083&v=e