Quick answer: The cost to run a space heater for eight hours starts as 12 kWh, everywhere. At the US average that is $2.20 and in Britain £3.13 until 30 September. But the US average is a fiction: the same night costs $1.57 in Nevada and $6.33 in Hawaii. The rate spans a factor of four; your heater’s two settings span two.
The arithmetic here is the easiest on this site. A 1,500 W space heater is resistive, so it draws its rated watts whenever the element is on. Eight hours is 12 kWh. That is the whole calculation, and it is the same in Nevada, in Hawaii and in Newcastle.
Everything difficult about this question is in the second number: what a kilowatt-hour costs you. Our appliance wattage chart prices everything at the US national average, because a chart has to pick something. This article is about how badly that single figure can mislead you — and about a change to the British number that lands on 1 October 2026.
Four times the price for the identical night
The EIA’s residential price table for June 2026 runs from 13.11 cents per kWh in Nevada to 52.72 cents in Hawaii. That is a factor of four, and within this sum it is the only thing that moves.
| Where | Price per kWh | One 8-hour night | 30 nights |
|---|---|---|---|
| Nevada, the cheapest state | 13.11¢ | $1.57 | $47.20 |
| Louisiana | 13.49¢ | $1.62 | $48.56 |
| US average | 18.34¢ | $2.20 | $66.02 |
| Massachusetts | 29.61¢ | $3.55 | $106.60 |
| California | 34.74¢ | $4.17 | $125.06 |
| Hawaii, the most expensive | 52.72¢ | $6.33 | $189.79 |
Two things follow. The first is that a national average describes almost nobody: 32 of the 51 entries in that table sit at or below 18.34 cents, so in most states the chart figure overstates the cost. The second is that shopping for a cheaper heater will not move this number. Every 1,500 W heater draws 1,500 W, so the appliance is fixed. The rate you can influence only slowly, by changing tariff or supplier. Hours are the term that answers today.
Britain has one price, and it changes on 1 October
Britain caps the unit rate, so the spread that dominates the American answer barely exists. What Britain has instead is a date. The Ofgem cap for the quarter we are in runs to 30 September 2026, and the next one is already published.
| Direct Debit, England, Scotland and Wales | 1 Jul – 30 Sep 2026 | 1 Oct – 31 Dec 2026 |
|---|---|---|
| Electricity unit rate | 26.11p | 26.32p |
| Daily standing charge | 57.19p | 54.83p |
| VAT included in the unit rate | 5% | none |
| One 8-hour night at 1,500 W | £3.13 | £3.16 |
| 30 nights | £94.00 | £94.75 |
That VAT line is doing more work than it looks. The 26.11p you pay today includes 5 per cent VAT, so the rate underneath it is 24.87p. The 26.32p from October has no VAT in it at all. On a like-for-like basis the underlying rate rose about 5.8 per cent; what actually leaves your account rose 0.8 per cent. Both statements are true, which is exactly why Ofgem tells you not to compare the periods directly.
The standing charge is not a running cost
Britain also charges you 57.19p a day before you switch anything on — £208.74 a year. It is tempting to fold that into “what the heater costs”, and it is wrong to: you pay it whether the heater runs or not. Every figure in this article is the unit rate only, which is the number that actually changes when you press the button.
The standing charge does decide who wins from the October change, though. The unit rate goes up 0.21p and the standing charge comes down 2.36p a day, so the break-even is 11.24 kWh a day. Below that you are better off from October; above it, worse. One 8-hour night on a 1,500 W heater is 12 kWh on its own — enough to push a household past the line before anything else in the building is counted.
What this costs on batteries instead
Grid electricity is cheap enough that the eight-hour night is an annoyance. On stored power it is impossible. Twelve kilowatt-hours is roughly twelve 1,024 Wh power stations emptied back to back. No portable unit is sized for that, and a large home battery would spend almost its entire charge heating one room for one night. That is the point the watts article makes and the money does not: a load can be trivial on the grid and hopeless off it.
Compare the other direction too. Twelve kilowatt-hours is what a router at 8 W uses in 62 days, or what a coffee maker spends brewing about a hundred pots. One heater, one night.
Cost is the least important reason not to run a heater unattended overnight. A 1,500 W heater is 12.5 amps on a 120 V circuit, and the US Fire Administration’s figures on heating fires are the reason this site keeps repeating that it belongs on its own outlet, never on an extension lead or a power strip.
Rates change. Check your own bill rather than any figure here before making a decision that depends on it. If you are preparing before the power goes, plan heat as the load you cannot back up. And a generator lives outside, well away from windows and doors, because carbon monoxide is odourless and kills quickly.
Frequently asked questions
How much does it cost to run a space heater for 8 hours?
Twelve kilowatt-hours, so it depends only on your rate. $2.20 at the US average, $1.57 in Nevada, $6.33 in Hawaii, and £3.13 in Britain at the current capped rate.
Is a 750 W setting half the cost?
Per hour, exactly half. Over an evening, only if the heater has no thermostat. With one, the room’s heat loss sets the energy used and the setting mostly changes how fast you get there — which the watts article takes apart in full.
Should I add the standing charge to the cost?
No. You pay 57.19p a day whether the heater runs or not, so it is not part of what running it costs. It is part of your bill, not part of this decision.
Does the October 2026 price cap make heating cheaper or dearer?
Dearer if you use a heater. The unit rate rises 0.21p and the standing charge falls 2.36p a day, so households under 11.24 kWh a day gain and heavier ones lose. A single 8-hour night is 12 kWh by itself.
Why does the EIA publish two different US averages?
Because it publishes two tables. The single month of June 2026 was 18.34 cents; the year to date through the same month was 18.16. This site uses the monthly figure throughout, including here. It is a good illustration of how little “the” price means.
This article is general information, not an installation guide and not a substitute for a licensed electrician. Electrical work on a service panel, a transfer switch or a utility connection is regulated in most jurisdictions and normally requires a permit and an inspection. Fuel-burning equipment produces carbon monoxide and must never be run indoors, in a garage or near an opening into the home.
