How Much Does It Cost to Run a Space Heater? (1500W Heat Cost Guide)

The formula: watts to dollars in one step

Every electric resistance heater converts essentially 100% of the electricity it draws into heat, so the maths is simple and there is no efficiency rating to look up. Divide the wattage by 1,000 to get kilowatts, multiply by the hours you run it, then multiply by your rate per kWh. A 1,500W heater is 1.5 kW; run it for 6 hours at $0.18/kWh and you get 1.5 × 6 × 0.18 = $1.62 per evening. Multiply by 30 and a single heater in one room adds about $49 a month. Two heaters in a drafty house through a long northern winter routinely add $200-$300 a month.

Cost per hour by electricity rate

Rates vary enormously by state and by supplier, which is why a national average is only a starting point. California residential rates commonly exceed $0.30/kWh and Hawaii is higher still, while parts of the Midwest and the South sit near $0.12/kWh. In the UK, the Ofgem price cap has kept unit rates in roughly the 24p-28p/kWh band, with a separate standing charge of about 50p-60p per day that you pay whether or not you switch the heater on. Enter your own rate in the calculator on the home page to get a figure that matches your bill rather than an average.

• $0.12/kWh (low-cost US state): $0.18 per hour, about $43 per month at 8 h/day
• $0.16/kWh (US average): $0.24 per hour, about $58 per month
• $0.30/kWh (California-style rate): $0.45 per hour, about $108 per month
• 26p/kWh (UK price cap): 39p per hour, about £94 per month plus standing charge
• €0.30/kWh (typical EU): €0.45 per hour, about €108 per month

Thermostats, eco mode and why 1500W is not always 1500W

A heater on its thermostat does not draw full power the whole time. Once the room reaches the setpoint the element cycles off, so a heater described as 1500W may average 700-900W over an evening in a well-insulated room, and close to the full 1,500W in a poorly insulated one. Oil-filled radiators cycle more gently and feel steadier, but they produce exactly the same heat per kWh as a ceramic fan heater. Any claim that one resistance heater is more efficient than another is marketing: the only real savings come from heating a smaller space, for fewer hours, at a lower setpoint.

Space heater vs central heating: when each one wins

A space heater wins when you are heating one occupied room and turning the whole-house thermostat down by several degrees. Dropping a central system by 7-10°F for eight hours a day saves roughly 10% of annual heating costs, and if a single 1,500W heater covers the room you are actually in, the trade is usually positive. A space heater loses badly when it is used to heat several rooms, or when it supplements a heat pump. A modern heat pump delivers 2.5-4 units of heat per unit of electricity, so it produces the same warmth for a quarter to a third of the cost of resistance heat. If you own a heat pump, running space heaters instead of it is the most expensive heating decision available.

Six ways to cut heater running costs this winter

• Use a plug-in timer or a smart plug so the heater cannot run all night unattended
• Set the room thermostat to 68°F / 20°C; every extra degree adds roughly 6-8% to heating energy
• Close the door and heat only the occupied room; draft-proof the door sweep and window frames
• Never run a heater on an extension lead: 1,500W is at the safe limit of a 15A US circuit
• Move the load off-peak where a time-of-use tariff exists, and pre-heat before the peak window begins
• Compare against a heat pump or a mini-split before buying a second heater

Space heater running cost by wattage and rate (8 hours per day, 30 days)

Frequently asked questions

How much does it cost to run a 1500W heater for 24 hours?

1500W for 24 hours is 36 kWh. At $0.16/kWh that is $5.76 per day, or about $173 a month. At a UK rate of 26p/kWh it is £9.36 per day.

Is a space heater cheaper than central heating?

Only when it lets you turn the whole-house thermostat down and heat a single occupied room. Compared with a heat pump it is two to four times more expensive per unit of heat, and compared with gas heating it is usually more expensive per BTU in most US and UK markets.

Do oil-filled radiators use less electricity than fan heaters?

No. Both convert electricity to heat at essentially 100%. An oil-filled radiator holds heat longer and cycles less abruptly, but at the same wattage and run time the kWh consumed is the same.

How many watts does a space heater use on low?

Most 1,500W models offer a 750W or 900W low setting, which halves the running cost but also halves the heat output, so the room takes longer to reach temperature.