Heating and power, cost per kWh
Portable power stations: the cost per stored kWh
A portable power station never beats the grid on price and cannot, because every kilowatt hour it delivers was bought from the grid first and then charged storage on top. What it is actually for is the times when there is no grid.
Some links on this page are affiliate links, which earn us a commission if you buy. It costs you nothing extra, and it never changes which option comes out cheapest here, because the ranking is arithmetic. How this works.
The answer nobody selling one will lead with
Grid electricity costs 26.1p a kilowatt hour. The best power station on this page delivers the same kilowatt hour for about 52.3p, and the cheap one for about 91.5p. Storage roughly doubles or trebles the price of electricity you have already bought.
| Option | Running | Cost per kWh delivered | Relative |
|---|---|---|---|
| Straight from the socketno storage at all | 26.1p | 26.1p | |
| Power station, lithium iron phosphate£700, 1 kWh, 3,000 cycles | 29p | 52.3p | |
| Power station, older lithium ion£500, 1 kWh, 800 cycles | 29p | 91.5p | |
| Petrol generator£350, 2kW | £1.51 | £3.01 |
That is not a criticism of the product. It is what storage is. Every kilowatt hour in the battery was purchased from the socket at 26.11p per kWh, lost about a tenth of itself going in and coming out, and then had a share of a £700 battery added to it.
Cycle life is the entire specification
The cheaper unit costs 70% as much and lasts a bit over a quarter as long, which makes its stored electricity nearly twice the price. Lithium iron phosphate cells are the thing to look for and cycle life is the number that decides this, far more than capacity or the number of sockets on the front.
A rating like 3,000 cycles normally means 3,000 full charges before the battery holds 80% of what it did when new, not before it stops working. It also assumes reasonable temperatures and not sitting at full charge for months. Store it around half charged if it will be idle, which costs nothing and materially extends its life.
What it is actually worth buying for
Three things, none of which is saving money. Running something when there is no mains at all, which is camping, a stall, a shoot or a power cut. Running something where a generator is unacceptable, which is anywhere indoors, anywhere quiet, and most of a campsite. And shifting a fixed amount of load to a cheap overnight rate, which is the one case where it can genuinely pay.
The one case where the arithmetic works
Charge on an overnight EV rate at 7p per kWh and discharge during the day, and the electricity in the battery costs 7p per kWh a kilowatt hour instead of 26.11p per kWh, a saving of about 19p. Against 23p a kilowatt hour of battery depreciation on the better unit, that still does not quite pay. It only starts to work with a much cheaper battery, a much longer cycle life, or solar panels charging it for nothing.
Against a generator
A petrol generator produces a kilowatt hour for about £1.51 in fuel alone and needs servicing, so on pure cost it is worse than either battery. It wins on one thing only, which is that you can keep pouring petrol into it and it will run all week, where a 1 kWh battery is empty after an hour of a kettle. For a long outage that difference matters more than the price does.
The verdict
Buy one for silence, portability and power cuts, and buy lithium iron phosphate with a high cycle rating rather than the cheapest unit with the biggest number on the box. Do not buy one to save money on electricity, because it cannot, and any calculation that says otherwise has left out the battery.
Put your own numbers in
The purchase price divided by cycles is what decides this. Change the cycle life and the price to match the unit you are looking at.
Cost per meal
Set the purchase price to zero for the running cost alone.
Questions
Can a portable power station save money on electricity?
No. Every kilowatt hour it delivers was bought from the grid first, lost about 10% in the round trip, and then carries a share of the battery's cost. Grid electricity is 26.1p a kWh and stored electricity is about 52.3p.
How much does a power station cost per kWh?
About 52.3p a delivered kilowatt hour for a £700 lithium iron phosphate unit rated at 3,000 cycles, and around 91.5p for a cheaper unit rated at 800.
Is LiFePO4 worth paying more for?
Yes, and it is the main thing to look for. It costs about 40% more up front and lasts nearly four times as many cycles, which almost halves the cost of every stored kilowatt hour.
Is a power station cheaper than a petrol generator?
Per kilowatt hour, yes. A generator burns roughly 0.9 litres of petrol per kWh, about £1.51 in fuel. A generator wins only on being able to run for days rather than an hour.
What is a power station actually good for?
Power cuts, camping, market stalls and anywhere indoors or quiet where a generator is not an option. It is a convenience and resilience purchase, not a saving.
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More heating and damp costs, or read how we work these out.
Prices used on this page
- Electricity, 26.11p per kWh. Ofgem price cap, direct debit, average of England, Scotland and Wales, including 5% VAT.. Ofgem energy price cap unit rates and standing charges. Checked 22 August 2026.