Electric Heater Running Cost Calculator
Estimates the daily, monthly and seasonal running cost of an electric space heater from its power rating, hours of use and your electricity rate.
A 1,500 W electric space heater that runs 5 hours a day on 22 days a month uses 165 kWh in that month, or about 825 kWh over a five-month heating season. Multiply those kilowatt-hours by the price per kWh on your electricity bill to get the cost.
The arithmetic is direct. An electric resistance heater turns almost all of the electricity it draws into heat, so there is no multiplier to apply. A 1,500 W forced-air heater draws 1.5 kWh of electricity every hour it runs at full power, whether the room is cold or nearly warm. The monthly figure therefore depends almost entirely on how many hours the heater runs.
This differs from a heat pump, which moves heat from outside air or the ground into the building and delivers more heat than the electricity it consumes. Heat pump efficiency is expressed as a coefficient of performance (COP), while a resistance heater always has a COP of 1.0. Two heaters in separate rooms add up quickly, because each one draws its own load for as long as it runs.
Real use varies. Most heaters have a thermostat that switches the element off once the room reaches the set temperature, so the heater may run at full power for less time than it is switched on. The calculator assumes full power for the hours you enter, which makes the result an upper estimate for that pattern of use. Enter the hours you actually observe, or estimate them from how often the heater cycles on.
The calculator turns that arithmetic into a daily, monthly and seasonal energy figure, then into a cost once you enter your rate. It is most useful for comparing scenarios, such as one heater against two, or short sessions against long ones, before you decide how to heat a room.
The explanation below uses US units; the calculator works in either system.
The result updates automatically.
Fast heating by forced convection. Typical models: 750 W-2,000 W.
Shown on the unit's label. E.g.: 1,500 W = 1.5 kW.
Average operating time. In homes without central heating, 4-8 h/day is common in winter.
In December and January, count 25-30 days. In milder months (October, March), fewer.
Electricity prices in the United States vary by state, utility, rate plan and usage tier. Use the price per kWh from a recent bill, or your total electricity charge divided by total kWh if your rate is tiered or time-of-use.
Estimated monthly cost
consumption: 150.0 kWh/month
- Consumption per hour
- 1.5 kWh
- Cost per hour
- $0.33
- Daily consumption
- 7.5 kWh
- Monthly consumption
- 150.0 kWh
- Seasonal cost (5 winter months)
- $165.00
How it works
Formula
How the calculation works
Electric Heater Running Cost: How the Calculation Works
This calculator estimates how much electricity an electric space heater uses per hour, per month and over a heating season, then converts that energy into a cost using the price per kWh you enter. It applies to forced-air heaters, quartz and infrared heaters, oil-filled radiators and panel heaters, because all of them turn electricity into heat through a resistance element.
The formula works in metric units, and the calculator's unit toggle converts the displayed values automatically, so the same arithmetic applies whichever system you view. The result is an estimate of the electricity the heater draws while it runs, which makes it useful for comparing options before you buy a heater or decide how to heat a room.
How the formula works
The calculation has three inputs: the rated power of the heater, the hours it runs each day, and the number of days it runs each month. Daily energy is power multiplied by hours. Monthly energy is daily energy multiplied by days. The cost is monthly energy multiplied by the price per kWh on your electricity bill.
Power is expressed in kilowatts (kW), so 1,500 W becomes 1.5 kW. Energy is measured in kilowatt-hours (kWh), the unit used on your bill. A 1.5 kW heater running for 4 hours uses 6 kWh per day. Over 20 days, that is 120 kWh per month. Multiply 120 kWh by the price per kWh on your bill to get the monthly cost.
The formula does not include the heat needed by the room or the insulation of the building. It answers one question: how much electricity does this heater draw under the stated pattern of use? That is why the hours of use carry most of the uncertainty in the result.
Why electric resistance heating costs more per unit of heat
An electric resistance heater passes current through a heating element. Almost all of the electricity drawn becomes heat, so the efficiency is close to 100%. In the terms used for heat pumps, the coefficient of performance (COP) of a resistance heater is 1.0. A heat pump, by contrast, moves heat from outside air or the ground into the building. For the same heat delivered, it draws less electricity than a resistance heater.
This difference is the main reason electric resistance heating is expensive to run as a primary heat source. A heater is cheap to buy and simple to install, but each kilowatt-hour it uses produces only one kilowatt-hour of heat. Other heating systems can deliver more heat from the same electricity, or run on a different fuel, so the cheapest option depends on local energy prices and the efficiency of the equipment.
Types of electric heaters
Most portable and wall-mounted electric heaters fall into four groups. The power ranges below are typical for each type. Always check the nameplate of the actual appliance.
| Type | Typical power | Best use |
|---|---|---|
| Forced-air heater | 750 W to 2,000 W | Fast warm-up in small rooms |
| Quartz or infrared heater | 800 W to 2,400 W | Direct heat for people and objects nearby |
| Oil-filled radiator | 750 W to 2,500 W | Steady heat in medium rooms over several hours |
| Panel heater | 500 W to 2,000 W | Permanent mounting in a living room or bedroom |
A forced-air heater warms the air quickly, but that warm air leaves the room soon after the heater is switched off. An oil-filled radiator heats slowly and keeps releasing heat from its oil after it is switched off. In a room occupied for several hours, that stored heat can be useful, but the heater still draws full power while its element is on. Allow time for an oil-filled radiator to warm up before you need the heat.
All four types are resistance heaters, so the calculation is the same for each. The type affects comfort and how the heat feels in the room. It does not change the electricity used per hour at a given power rating.
Thermostats and real run time
Most heaters have a thermostat that switches the heating element off when the room reaches the set temperature and back on when the room cools. While the element is on, the heater draws its full rated power. A 2 kW heater with a working thermostat still uses 2 kW during the time it is on. What changes is the share of time the element is energized.
The calculator cannot know that share. It assumes the heater runs at full power for the hours you enter. If you know the heater cycles on and off, enter the hours during which the element is actually heating, not the hours the appliance is switched on at the wall. A plug-in energy monitor can measure real consumption over a few days and give a more reliable figure.
How much a thermostat reduces run time depends on the room's insulation, the outdoor temperature, how often the door or windows open, and where the thermostat sensor sits. A well-insulated room on a mild day may need very little running time, while a drafty room on a cold night may need the element on almost continuously. Lowering the set temperature by a few degrees generally reduces run time, because the room settles at a lower temperature and holds it with less energy.
Seasonal cost over a five-month heating season
The calculator also estimates a seasonal total using five months of winter use, for example from November through March. Many households do not use electric heat for the whole season, so the seasonal figure is an upper estimate that assumes the same daily pattern throughout.
Consider a two-bedroom apartment in Chicago with two 1,500 W heaters, one in the living room and one in the bedroom. Each runs 5 hours a day on 22 days a month. The monthly energy is 2 × 1.5 kW × 5 hours × 22 days, which is 330 kWh. Over five months, that becomes 1,650 kWh. A single heater used the same way would use half of that.
Compare this with a heat pump that delivers the same 330 kWh of heat. At an illustrative COP of 3.5, the electricity needed would be about 94 kWh per month. Real heat pump performance depends on outdoor temperature, equipment and installation, so treat this figure as an illustration of the principle, not a forecast for your home.
Electrical circuit check on 120 V
In most US homes, general-purpose outlets supply 120 V. Current in amps equals power in watts divided by voltage. A 1,500 W heater on a 120 V circuit draws 12.5 A (1,500 ÷ 120). Two such heaters on the same circuit draw about 25 A together.
The National Electrical Code (NEC, NFPA 70) generally limits continuous loads to 80% of a circuit's rating. A continuous load is one expected to run for three hours or more. On a 15 A circuit, that limit is 12 A, so a 1,500 W heater already exceeds it when it runs for long periods. Local electrical rules apply, and a licensed electrician can confirm what a given circuit can safely support.
Heaters are also made for other supply voltages. For the same power, a heater on a different supply voltage draws a different current, so the circuit requirements change. The energy used in kWh stays the same, because the calculator works from power and time. Voltage changes the current and the circuit requirements, not the kilowatt-hours on the bill.
Common mistakes that raise the bill
The most frequent mistake is setting the heater to its maximum and then opening a window because the room has become too warm. The warm air escapes, and the heater works at full power again when the window closes. A moderate setting with the thermostat managing the cycle usually gives a more predictable result.
A second mistake is using an average rate from memory instead of the actual price per kWh. Many utilities use tiered or time-of-use rates, so the price per kWh can change during the month. To find an average, divide the total electricity charge by the total kWh on a recent bill, and exclude fixed fees if you want the energy rate alone.
A third mistake is adding heaters without counting them. A second heater in another room doubles the monthly figure for that room's pattern of use, and the total can exceed what people expect from a single appliance.
Finally, many people forget how long an oil-filled radiator takes to warm up, and then leave it running longer than necessary. Switch it on earlier, and shorten the run time if the room warms up quickly.
When an electric heater is not the right solution
Electric resistance heating suits occasional use: a rarely used room, a garage workshop, a home office used only some days, or an extra source of heat on an unusually cold day. It is less suited to heating a whole home every winter, because it converts electricity into heat one-for-one, and other systems can deliver more heat from the same energy.
For regular whole-home heating, a heat pump is generally more efficient than resistance heating, because it moves heat instead of generating it. Its performance depends on the climate, and in very cold weather its heating capacity can drop. The system should be sized by a qualified professional using a room-by-room heat load calculation. A licensed HVAC contractor can compare a heat pump, a gas furnace and electric resistance options against the energy prices in your area.
Improving insulation, sealing gaps around doors and windows, and fitting draft stoppers reduce the heat a room needs, which shortens the run time of any heater. The benefit depends on the building, so a professional home energy assessment can point to the measures that will help most.
Limits of this calculator
The calculator uses the rated power of the heater, not a measured draw, and assumes that power stays constant while the heater runs. It does not model heat loss from the room, so it cannot say whether a heater is large enough to reach a set temperature. It also assumes one flat price per kWh. If your bill uses tiered or time-of-use rates, enter an average price taken from a recent bill.
Use the calculator to compare patterns of use and to estimate the order of magnitude of the cost. For a precise figure, combine the nameplate, a plug-in energy monitor and your actual electricity bill. For any new circuit or permanent installation, consult a licensed electrician.
Where to find reliable reference data
The U.S. Energy Information Administration (EIA) publishes average residential electricity prices and consumption data by state, which can help you judge whether your rate is typical for your area. Your utility's rate schedule and your own bill are the most accurate sources for your home.
Frequently asked questions
How much electricity does a 2,000 W heater use per hour?
A 2,000 W (2 kW) heater uses 2 kWh of electricity for each hour it runs at full power. At 5 hours a day on 20 days a month, that is 200 kWh per month from one appliance. To turn that into a monthly cost, multiply the kWh by the price per kWh on your electricity bill. Also check the circuit: at 120 V, a 2,000 W heater draws about 16.7 A, which is more than a 15 A circuit can carry. Confirm the nameplate rating and have a licensed electrician check any circuit before you plug it in.
Which electric heater type has the lowest running cost?
Electric resistance heaters convert nearly all of their electricity into heat, so the heater type matters less than the power rating and the hours of use. A 1,500 W heater that reaches the set temperature quickly and then cycles off may use less energy than a larger heater left on all evening. Oil-filled radiators keep releasing heat after they are switched off, which can make a room comfortable for longer, but they still draw full power while the element is on. Compare heaters by their wattage and by the hours you realistically run them.
How much electricity does a 1,500 W heater use in a month?
It depends on the hours of use. At 4 hours a day for 20 days, a 1.5 kW heater uses 1.5 × 4 × 20 = 120 kWh. At 6 hours a day for 25 days, usage rises to 225 kWh, which is a heavy-use pattern. To estimate the cost, multiply the kWh by the price per kWh on your bill. Use the calculator to get the exact figure for your own rate and pattern of use.
Is a heat pump cheaper to run than an electric heater?
For the same amount of heat, usually yes. A heat pump moves heat rather than generating it from resistance, so it delivers more heat than the electricity it consumes, measured as a coefficient of performance (COP). A COP above 1.0 means less electricity than a resistance heater needs for the same heat. The actual saving depends on the heat pump's efficiency rating, the outdoor temperature and the building's insulation. Heat pumps lose capacity in very cold weather, so a licensed HVAC contractor should size the system with a room-by-room heat load calculation.
Does the thermostat reduce electricity use?
Yes, but only because it switches the element off once the room reaches the set temperature. While the heater is on, it still draws its full rated power: a 2 kW heater with a working thermostat uses 2 kW while the element is energized. What changes is the share of time the element runs. How much that reduces run time depends on insulation, outdoor temperature and how often the room is opened. Enter the hours you actually observe in the calculator, not the hours the appliance is switched on.
Does the voltage of my heater change the cost?
Not the energy use. The calculator works from rated power and hours, and the kilowatt-hours for a given power and running time are the same at any supply voltage. Voltage changes the current a heater draws, which matters for circuit capacity and breaker ratings. A 1,500 W heater draws about 12.5 A at 120 V, the standard supply in most US homes. Check the voltage on the nameplate and have a licensed electrician confirm that the circuit can carry the heater's current.
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By RivoCalc · Reviewed under our editorial methodology · Updated June 3, 2026
Results are estimates based on the rated power and the hours you enter. Real consumption varies with the heater's actual output, thermostat cycling, room insulation, outdoor temperature and how often the heater is used. Electricity prices vary by utility, rate plan and usage tier, so check your bill. This calculator does not replace an electrical safety check or a heat load calculation by a qualified professional.