How Much Does It Cost to Run a Space Heater?

How much does it cost to run a space heater per hour?

About 27 cents an hour. That is a 1,500 W heater — the most common size sold in North America — running on high at the U.S. residential average of 18.16¢ per kilowatt-hour. It is not a rounding convenience: 1,500 W is 1.5 kilowatt-hours for every hour the element is energised, and 1.5 × $0.1816 = $0.2724. A heater is one of the highest-wattage things a normal wall outlet is ever asked to carry, which is why an "extra hour" of comfort is worth more than an extra hour of almost anything else in the house.

Every one of those numbers comes from two steps, and the only input that changes between neighbours is the rate:

kWh = watts × hours ÷ 1,000, then cost per hour = watts ÷ 1,000 × your rate

Work through it at each size, at 18.16¢/kWh:

• 600 W (a small radiant or ceramic desk unit): 0.6 kWh an hour = 11¢.
• 750 W (the low setting on a typical 1,500 W heater): 0.75 kWh = 14¢.
• 1,000 W: 1 kWh = 18¢ — one kilowatt-hour exactly, so the cost per hour equals your rate.
• 1,500 W: 1.5 kWh = 27¢.
• 1,800 W: 1.8 kWh = 33¢.
• 2,000 W (the ceiling for a plug-in unit on a 15 A circuit): 2 kWh = 36¢.

Where you live moves this more than the size of the heater does. The same 1,500 W element costs 14¢ an hour on a Washington-state bill and 41¢ an hour in the priciest parts of New England or Alaska — a three-fold spread for identical warmth. Check your actual ¢/kWh on a bill line before trusting any published table, including the ones below; that single number is worth more than any other adjustment you can make here.

What does each size cost per day, month and season?

Three lengths of time matter when you are deciding whether a heater is affordable for a winter: the 8-hour work or sleep day, the 30-day billing cycle, and the November–March heating season of 151 days. Each row below assumes the element is energised for the whole window — the worst case a thermostat can produce, which makes these figures a ceiling rather than a forecast.

Read the 1,500 W line as the reference point: 1,812 kWh and $329.06 over a full heating season if it ran eight hours a day without the thermostat ever satisfying. The next section explains why the number you actually pay is typically half that. The other reading is worth taking too — a $26.15 month at 600 W versus $65.38 at 1,500 W is the cheapest lever you can pull, because a small room rarely needs 1,500 W to hold temperature once it is already warm.

Both scales are linear, so you can stretch these rows to any schedule without recalculating from scratch. Halve the hours and you halve the cost: the 1,500 W row becomes $32.69 a month at four hours a day and $98.06 at twelve. Then multiply any cell by your own rate divided by 18.16 — a 25¢/kWh state multiplies everything by 1.38, a 12¢/kWh state by 0.66. And keep the figures in proportion: a 100 W television left on for the same eight hours a day costs $4.36 a month on this exact basis, so a single 1,500 W heater on high is roughly fifteen televisions running continuously. That is the honest framing for a space heater — not an expensive appliance, but an expensive hour.

Why your real bill is lower than the nameplate maths

Nearly every article about heater cost quotes the continuous figure and stops there. The reason your bill does not match it is the duty cycle: the share of time the element is actually energised while the heater is switched on. A space heater is not a light bulb. Its thermostat reads the air around it, and as soon as that air reaches the set point the element cuts out entirely — the fan may keep spinning, the housing stays warm, but you are drawing tens of watts instead of 1,500. It restarts when the temperature drops back below the set point. The average draw over an hour is therefore nameplate watts × duty cycle, and duty cycle is what you are really buying.

How long the element stays off depends on how fast the room leaks heat:

• A small, well-insulated interior room — a home office with no exterior wall, a bedroom already sharing heat from the rest of the house — typically holds 30–50% duty once it is warm. The element runs a couple of minutes, rests for five or more.
• A drafty space — a 1970s bedroom with single glazing, a finished garage, a cabin, a room with a door that gets opened every few minutes — runs close to 100%. The heater is losing the race, and the nameplate figure is your real bill.
• The first hour of any session is always near 100%, because cold walls and furniture absorb heat faster than the room can give it back. Cheap run time comes after the room reaches temperature, not before it.

The word "continuous" on the packaging is the other source of confusion. It means the heater is listed to survive running without a break without overheating — a safety rating, not a statement about how it will behave on your thermostat. Size your circuit for the continuous number; budget your bill for the duty-cycle number.

You can measure yours in ten minutes. Get the room to temperature, leave the heater on its thermostat setting, and watch the power indicator: count the minutes the light is on across a half hour and divide by 30. Multiply the result by the 1,500 W ceiling in the table above and you have your own monthly cost, with no assumptions borrowed from anyone else's article.

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

A 1,500 W heater left on high for a full day-and-night draws 1.5 kW × 24 h = 36 kWh, before the thermostat intervenes. Multiply by your rate and the spread across the country is enormous — from $4.32 to $12.60 for exactly the same 36 kWh, which is why a "space heaters cost $X a month" claim from a national blog is meaningless without a rate attached.

Two practical notes on the 24-hour figure. First, treat it as a ceiling, not an expectation: a thermostat-controlled heater in a closed room rarely holds 100% duty across a full day, so a realistic all-day cost at the U.S. average is nearer $3.27 at 50% duty than $6.54. Second, that ceiling is the number to use for an unattended room — a heater guarding a frozen pipe, a pet's room overnight, a holiday house you check once a week — where the thermostat genuinely never satisfies and the element really does run the whole time.

Compounded, the all-day case is where winter bills get away: $6.54 a day is $196.13 a month and $2,386.22 across a year, roughly what a season of central heat costs on a much cheaper fuel. Two adjustments make the number yours rather than mine. If you are on a time-of-use tariff, a 24-hour window straddles peak and off-peak hours, so replace 18.16¢ with the blended average your bill implies (total cost divided by total kWh for the month) before reading the table. And if the heater is on a timer for 24 hours but not on high the whole time, work from kilowatt-hours directly: 36 kWh = 1.5 kW × 24 h, then multiply by whatever rate you settled on. The appliance calculator runs the same arithmetic at your exact watts, hours and rate if you would rather not do it by hand.

How many amps does a space heater draw, and will it trip the breaker?

Divide watts by volts: amps = watts ÷ volts. A 1,500 W heater on a standard 120 V outlet draws 12.5 A. A 1,800 W model draws 15 A; a 2,000 W model draws 16.7 A. Those are not comfortably inside a bedroom circuit — they are at or past the ceiling of the one most homes wire rooms with.

A 15 A breaker is rated to carry its full 15 A for short periods, but the National Electrical Code sizes conductors and overcurrent devices for continuous loads at 80%. NEC 210.20(A) means a load expected to run three hours or more should not exceed 12 A, and a space heater on a thermostat through a winter night is exactly that kind of load. Twelve amps at 120 V is 1,440 W — so a 1,500 W heater on high already exceeds the sustained rating of a 15 A circuit by about 60 W. A 20 A circuit is the clean fit: 80% of 20 A is 16 A, or 1,920 W, which leaves the 1,500 W heater running inside its continuous limit with headroom to spare.

In practice the heater will usually run on a 15 A circuit without tripping, precisely because duty cycle pulls the average down. What trips it is company on the circuit: a fridge compressor starting, a shop vacuum, a hair dryer, a second heater on the same run of wall. If the breaker on your heater's circuit has already gone once, that is a wiring-capacity problem and not something a longer extension lead solves. See how many watts a circuit can handle for the 80% rule applied breaker by breaker, and the amps to watts calculator to convert your heater's label. Plug a heater straight into the wall — never into a power strip or a light-duty extension cord, both of which can overheat well below the current they appear to tolerate.

Is a space heater cheaper than central heat or a heat pump?

It depends entirely on how much of the house you actually need warm. Resistive heating — every oil-filled radiator, ceramic fan unit and baseboard strip — converts electricity to heat at close to 100% efficiency: 1 kWh in is 1 kWh of heat out, or about 3,412 Btu. There is no efficiency to lose, which also means there is no efficiency to gain. You cannot make a plug-in heater cheaper than its wattage.

A heat pump is the different case, because it moves heat instead of making it. At a coefficient of performance (COP) near 3, that same 1 kWh of electricity delivers roughly 3 kWh of heat, so the effective cost of warmth is about a third: around 6.05¢ per kilowatt-hour of heat instead of 18.16¢. A modern cold-climate unit at COP 2.5 still beats resistance by 2.5 times. Even a gas furnace at ~90% annual efficiency is delivering heat at a per-unit cost that resistance heating struggles to match for whole-house coverage.

So why do people save money with a space heater? Because the useful quantity is not heat produced, it is heat where you are. If you spend eight hours in one 120 sq ft room, central heat bills you for the hallway, the empty bedrooms and the unused bathroom as well. Closing those rooms and running a 1,500 W unit for $2.18 a day is a real saving when it lets you drop the thermostat for the whole house — and a real loss the moment the door is open and the "zone" leak is warming a corridor. Resistance heaters win only for spot-heating one or two occupied rooms; for anything bigger, the heat pump wins on physics.

Which setting is cheaper: low, high or eco?

The watts follow the setting, because the same element is doing the work. On a typical 1,500 W unit, high energises the full element at $0.27 an hour, low switches to the 750 W half-element at $0.14 an hour, and a fan-only mode with no heat uses only the blower motor — tens of watts, roughly 0.6¢ an hour, which is to say around $2.18 for a month of eight-hour days. If you are paying a "heating" bill that matches the fan-only figure, you are paying for air movement, not warmth.

Where people get caught out is assuming the cheaper-per-hour setting is the cheaper setting. Two units holding the same room at the same temperature burn almost the same energy per day: a 750 W element that runs continuously and a 1,500 W element that runs half as often both push the same kilowatt-hours through the walls, because the room's heat loss decides the total. High with a thermostat is usually the smarter choice, since the bigger element reaches the set point and cuts out; low in a cold room often means an element that never stops, at half the power but double the hours — and, on some models, more fan noise for the same bill.

The genuinely cheap setting is the one that lengthens the off time, so it is the target temperature and the timer, not the high/low switch:

• Eco or thermostat mode is the cheapest real option, because it is the only setting designed to switch the element off. Every degree you lower the set point cuts the duty cycle in a warm house.
• Low is the right call for a small room that is already warm — a desk, a bedside — where 750 W is enough to hold temperature without the element ever running long.
• High belongs to the first 30 minutes of a cold room, and to drafty spaces where low never catches up.

Keep reading

Comparing the heater with everything else on the circuit? Electricity cost of common appliances puts 40 devices on the same 18.16¢/kWh basis used here, so you can see that a space heater in an eight-hour day out-and-out beats a fridge's entire week. New to the tool? How to use the appliance electricity bill calculator walks through watts, hours and rates field by field. For the electrical side, the amps to watts calculator converts any label rating, and all energy tools collects the rest of the set.