How Much Electricity Does a Space Heater Use?

Space heaters are the one appliance where the marketing and the physics openly disagree. Every electric resistance heater turns essentially all the electricity it draws into heat, so a 1,500 W ceramic tower, a 1,500 W oil-filled radiator and a 1,500 W infrared panel cost exactly the same per hour of running. What actually differs is how the heat reaches you, and therefore how long the thermostat keeps the element switched on.

Why every 1,500 W heater costs the same to run

There is no such thing as a more efficient electric space heater. All of them are 100 percent efficient at converting electricity to heat, because heat is what electricity turns into when you make it fight through a resistive element. Claims that a particular heater will cut your bill in half are describing behaviour, not efficiency: you get a smaller bill if you heat one room instead of six, and that works with any heater.

So the wattage sticker is the whole story on cost. Most portable units are 1,500 W on high and 750 W on low, because 1,500 W is roughly the most you can pull from a standard 120 V outlet without tripping things. Larger 240 V garage and shop heaters go to 5,000 W and beyond, and they cost proportionally more.

Run time matters more than the setting

Here is where most cost estimates fall apart. A heater on a thermostat does not run continuously. Once the room reaches the setpoint the element switches off, and it only comes back on when the temperature drifts down. In a well-sealed bedroom the heater might run 20 minutes in every hour after the first half hour. In a drafty garage in February it might never switch off at all.

That means the honest way to estimate cost is to guess at running hours, not clock hours. If your heater is on from 6pm to midnight but the thermostat only calls for heat a third of that time, you are paying for two hours, not six. The table below assumes continuous running at each figure, so read it as the ceiling for that duration.

Your electricity rate does more damage than your heater

The same heater costs four times as much in Hawaii as it does in Idaho, and nothing about the heater changed. If you only remember one thing from this page, make it this: find the cost per kWh on your electricity bill and use that number instead of any national average, including ours.

Space heater running cost by state

Below is what a 1,500 W heater running six hours a day costs in every state, at current residential averages. Deregulated states are the ones where these figures move most, because your actual supply rate depends on the plan you are on rather than a single utility tariff.

When a space heater is genuinely the cheaper choice

Space heaters get a bad reputation they only partly deserve. Running one costs roughly $0.28 an hour, which is expensive per unit of heat compared with a heat pump and usually more expensive than natural gas. But heating one occupied room at 1,500 W while letting the rest of the house sit at 60 degrees can genuinely beat running a central system at full setpoint, and that is the case where the maths works.

It stops working the moment you use two or three of them, or leave one running in an empty room, or use one as the primary heat source for a whole floor. At that point you are paying resistance-heating prices for a whole-house load, and a heat pump delivering three units of heat per unit of electricity will beat it comfortably. Our heat pump versus gas comparison covers that trade in detail.

Five changes that actually lower the number

The savings that actually move the number, roughly in order of how much they are worth:

• Use the low setting when it holds temperature. 750 W instead of 1,500 W halves the running cost to about $0.14 an hour. In a small insulated room the low setting often keeps up fine once the room is warm.
• Turn the heater thermostat down, not the fan up. Every degree of setpoint you give back reduces how much of each hour the element runs.
• Put it on a plug-in timer or smart plug. The single biggest waste is a heater running in a room nobody is in, and a schedule fixes that without requiring discipline.
• Close the door and block the draft under it. Zone heating only saves money if the zone is actually sealed.
• Turn the central thermostat down at the same time. If you add a space heater without lowering the house setpoint, you have added a cost and removed nothing.

The circuit limit nobody reads until the breaker trips

A 1,500 W heater on 120 V draws about 12.5 amps. Standard household circuits are 15 or 20 amps, and continuous loads are supposed to sit at or below 80 percent of the breaker rating, which is 12 amps on a 15 A circuit. A single 1,500 W heater is therefore already at or slightly over the continuous-load limit for a 15 A circuit before anything else is plugged in.

In practice that means one heater per circuit, plugged directly into a wall outlet. Not an extension cord, not a power strip, and not sharing a bedroom circuit with a second heater. Space heaters are involved in a significant share of home heating fires every winter, and most of that is cord and outlet related rather than the heater itself failing. If you need to know what your circuit can carry, the watts, volts and amps calculator converts between the numbers on the label and the number on the breaker.

How this compares to everything else you plug in

Per hour of runtime, against the other things people use to stay warm. The mini-split figure is the interesting one: it moves heat rather than making it, which is why it does the same job for a fraction of the draw.

Questions people actually ask

Related running costs

Running it on solar

A space heater uses 9.00 kWh a day, which needs about 7 standard 400 W panels. Full array, battery and inverter sizing is on how many solar panels to run a space heater.

Run the numbers on your own bill

• Electricity Cost Calculator for your exact wattage and rate.
• Heat Pump vs Gas Heating Cost Calculator if you are weighing a permanent fix.
• Whole-Home Appliance Load Calculator to see where the heater sits against everything else.

Costs on this page use a national average residential rate of 18.44¢ per kWh (August 2026, EIA-derived state residential averages). Your own rate is printed on your electricity bill and is the number that actually matters. Every figure here is recalculated from one central rate setting, so these tables move when the national average moves.