house battery only installations
Discussion
Hi, has anyone done a battery only installation to pull from the grid when it is cheap overnight and then use throughout the day? no export to the grid.
I am regularly pulling average 20kwh per day due to WFH and various devices etc.
Appreciate installation of solar would offset usage throughout the day - in the process of trying to determine whether to build into the roof or not.
I am regularly pulling average 20kwh per day due to WFH and various devices etc.
Appreciate installation of solar would offset usage throughout the day - in the process of trying to determine whether to build into the roof or not.
Tye Green said:
some folk are doing that using their car's V2L function .e.g. Ioniq 5 / MG etc rather than a dedicated house battery but you still need to pay the daily standing charge to the leccy co
Will a 24kWh Nissan Leaf support the V2L function? For less than £2k it would make a cheap home battery if you have the space for a clunker on the drive plus it will get the cheaper EV tariff.And the bonus is you don't have to drive it!
Yes, an electrician I know did that.
From memory he has 12kwh of storage and pulls between 2 and 4 kwh a day from the grid.
I am never quite sure if it's actually worthwhile or just an exercise in wiring things up, almost as a demonstrator. His overnight electric costs about 7p/kwh, vs 21p (ish) at the moment on the price cap, so saving £1.70/day on power costs, or £600/year, and the upfront cost (wholesale, no labour) was about £5k, so 8 years payback.
Prices have come down since then, but there are some rough figures.
The advantage with solar + battery is the power is free (obviously), and batteries are 0 rated for VAT when installed with a renewable energy system. If you buy batteries on their own they are 20% VAT. Also, with solar + battery you can sell power back to the grid, and there are some really nice Time of Use Tariffs which enable you to sell power back into the grid at good prices later in the day, for example if you get 6/7p per kwh for exporting at 2pm, you might get 20p/25p for exporting at 6pm. You can then empty the battery, add a little charge overnight at cheap prices (or even just buy from the grid in the morning), until the solar charges them up again. That makes much better economic sense, than simply buying a battery or solar on their own.
From memory he has 12kwh of storage and pulls between 2 and 4 kwh a day from the grid.
I am never quite sure if it's actually worthwhile or just an exercise in wiring things up, almost as a demonstrator. His overnight electric costs about 7p/kwh, vs 21p (ish) at the moment on the price cap, so saving £1.70/day on power costs, or £600/year, and the upfront cost (wholesale, no labour) was about £5k, so 8 years payback.
Prices have come down since then, but there are some rough figures.
The advantage with solar + battery is the power is free (obviously), and batteries are 0 rated for VAT when installed with a renewable energy system. If you buy batteries on their own they are 20% VAT. Also, with solar + battery you can sell power back to the grid, and there are some really nice Time of Use Tariffs which enable you to sell power back into the grid at good prices later in the day, for example if you get 6/7p per kwh for exporting at 2pm, you might get 20p/25p for exporting at 6pm. You can then empty the battery, add a little charge overnight at cheap prices (or even just buy from the grid in the morning), until the solar charges them up again. That makes much better economic sense, than simply buying a battery or solar on their own.
Edited by Condi on Sunday 11th August 12:54
I do know someone who did this, because solar was a lot of hassle for his building.
The numbers only worked because he was getting relatively frequent power cuts and he was seeing a lot of value in having 'UPS' functionality for his WFH business.
It's a matter of tariffs, efficiency and crystal ball gazing, to know how many power cuts you might get in future and what tariffs might be available in 1,2, ...10 years' time.
A lot of people would do better to reduce their power consumption.
But with cells available for under £100 a kWh, some people could no doubt save a few quid.
Don't forget to allow for the round-trip efficiency of the Ac-DC-AC process.
The numbers only worked because he was getting relatively frequent power cuts and he was seeing a lot of value in having 'UPS' functionality for his WFH business.
It's a matter of tariffs, efficiency and crystal ball gazing, to know how many power cuts you might get in future and what tariffs might be available in 1,2, ...10 years' time.
A lot of people would do better to reduce their power consumption.
But with cells available for under £100 a kWh, some people could no doubt save a few quid.
Don't forget to allow for the round-trip efficiency of the Ac-DC-AC process.
Jeremy-75qq8 said:
I am looking at this at present. We use 60/70 kWh per day
We are on octopus agile which makes a decent reduction but 4-7pm at at a premium.
It is not my todo list. Batteries have come down a lot. Inverters have not
That is an awful lot of power, are you running a small steelworks at the bottom of the garden?We are on octopus agile which makes a decent reduction but 4-7pm at at a premium.
It is not my todo list. Batteries have come down a lot. Inverters have not
FMOB said:
Jeremy-75qq8 said:
I am looking at this at present. We use 60/70 kWh per day
We are on octopus agile which makes a decent reduction but 4-7pm at at a premium.
It is not my todo list. Batteries have come down a lot. Inverters have not
That is an awful lot of power, are you running a small steelworks at the bottom of the garden?We are on octopus agile which makes a decent reduction but 4-7pm at at a premium.
It is not my todo list. Batteries have come down a lot. Inverters have not
BigBen said:
I installed a battery only last year. I reckoned payback was about 3-4 years. I used a DIY battery kit from Fogstar and got the inverter second hand from Ebay.
I end up using almost no peak rate electricity. Tariff is intelligent Octopus GO as I have an EV.
What’s your daily usage? I end up using almost no peak rate electricity. Tariff is intelligent Octopus GO as I have an EV.
Condi said:
Yes, an electrician I know did that.
From memory he has 12kwh of storage and pulls between 2 and 4 kwh a day from the grid.
I am never quite sure if it's actually worthwhile or just an exercise in wiring things up, almost as a demonstrator. His overnight electric costs about 7p/kwh, vs 21p (ish) at the moment on the price cap, so saving £1.70/day on power costs, or £600/year, and the upfront cost (wholesale, no labour) was about £5k, so 8 years payback.
Prices have come down since then, but there are some rough figures.
The advantage with solar + battery is the power is free (obviously), and batteries are 0 rated for VAT when installed with a renewable energy system. If you buy batteries on their own they are 20% VAT. Also, with solar + battery you can sell power back to the grid, and there are some really nice Time of Use Tariffs which enable you to sell power back into the grid at good prices later in the day, for example if you get 6/7p per kwh for exporting at 2pm, you might get 20p/25p for exporting at 6pm. You can then empty the battery, add a little charge overnight at cheap prices (or even just buy from the grid in the morning), until the solar charges them up again. That makes much better economic sense, than simply buying a battery or solar on their own.
There are barely any examples of "V2H" at the moment in the UK, and "V2L" is not really intended for powering items in the house.From memory he has 12kwh of storage and pulls between 2 and 4 kwh a day from the grid.
I am never quite sure if it's actually worthwhile or just an exercise in wiring things up, almost as a demonstrator. His overnight electric costs about 7p/kwh, vs 21p (ish) at the moment on the price cap, so saving £1.70/day on power costs, or £600/year, and the upfront cost (wholesale, no labour) was about £5k, so 8 years payback.
Prices have come down since then, but there are some rough figures.
The advantage with solar + battery is the power is free (obviously), and batteries are 0 rated for VAT when installed with a renewable energy system. If you buy batteries on their own they are 20% VAT. Also, with solar + battery you can sell power back to the grid, and there are some really nice Time of Use Tariffs which enable you to sell power back into the grid at good prices later in the day, for example if you get 6/7p per kwh for exporting at 2pm, you might get 20p/25p for exporting at 6pm. You can then empty the battery, add a little charge overnight at cheap prices (or even just buy from the grid in the morning), until the solar charges them up again. That makes much better economic sense, than simply buying a battery or solar on their own.
Edited by Condi on Sunday 11th August 12:54
Batteries without solar have been 0% VAT since January 2024.
GB solar will do a 13.5 kWh AIO unit for £6,450 which I would contend provides just as quick if not quicker pay back time than a solar installation which would be around £11k for a 4 kW installation providing about 3000 kWh/annum depending on where you are in the UK, roof angles, access etc. etc. albeit it would probably have a slightly smaller battery.
Assuming a typical four bedroom user (4,000 kWh/annum), some minor load shifting (dishwasher and washing machine overnight), and that you can access an EV tariff, an AIO would probably push 95+% of your usage into a night time tariff.
The bill would go from £980/annum down to £318/annum (all ignoring the standing charge), saving £662. That is, a ten year pay back in the simplest of terms.
If you add solar, you are likely to make it so that 100% of your usage goes into night time. However, it is really difficult to work out what happens to the solar 3,000 kWh as some days it will be export and other days you will still need to import in the grid. Best value right now is to charge the battery overnight (7p/kWh) and export all the solar (15 p/kWh). Therefore, at absolute best case and assuming everything is exported, you could export all 3,000 kWh bringing in an additional £450/annum. So the "saving" per annum is £1150, that is, a ten year pay back in the simplest of terms. In practice, some of the export will be lost to charging the battery during the day so in this situation, it's likely that the battery only solution would be slightly better.
Obviously a lot of this depends on the person's usage. Somebody with a small electricity bill has less capacity to save (and exporting isn't going to make you rich).
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