How Much Power Does Your Heater Consume?

Glowing electric heater.
An electric space heater operating in a bedroom.

Heater operating costs are determined by a number of complex factors, especially due to the highly inconsistent temperatures that many areas experience during winter. This page provides electric heater power consumption data categorized by heater size, heater wattage, heater operating costs categorized by capacity, a little about other types of heaters, and will soon provide cumulative heater power consumption data organized by region. This article is focused on space heaters.

The monetary figures provided in this article are energy costs, unless otherwise stated.

Table Of Contents
Average Heater Energy Usage.
What Heater Power Ratings Mean.
Understanding Heater Wattage.
The Most Efficient Types Of Heaters.
Efficiency Of Condensing Vs. Non-Condensing Furnaces.
How To Reduce Furnace Gas Consumption.
Heat Pumps Vs. Fan Heaters.
Power Consumption Of Heaters By Size.

Average Heater Energy Usage

If you’re looking for average heater energy usage data for research purposes (not for financial planning), in temperate (mild) climates, the average household uses 5,000 kWh to 30,000 kWh of energy per year for heating. That equates to an average heating cost of $1,000 to $6,000 USD per year at an electricity rate of $0.20/kWh (without factoring in taxes and other fees that may be applicable in your region). A few examples of temperate climates are England, Iceland, and Germany.

Under some circumstances, a modern building may consume half as much energy for heating as an old leaky one would due to more energy-efficient designs.

Average Heater Energy Usage Per Home, Organized By Country

What Heater Power Ratings Mean

Heaters are usually equipped with a label, which provides electrical ratings, including the power consumption rate (this includes the heater wattage, which is measured in Watts). However, the cumulative energy usage of heaters is what you need.

The cumulative power consumption of a heater is equal to the heater’s wattage multiplied by the number of hours it is used per month if operated at the highest setting. This means that the daily power consumption (X) of an example 1,500 watt bedroom fan heater would be X = 1500 * 12 if it is used for 12 hours per day at the maximum setting.

Therefore, X would be equal to 18,000 Watts. Divide X by 1000 to convert it to kWh, which is a more convenient unit, and your result will be 18 kWh per day. The operating cost of an electric heater is determined by multiplying that kWh figure by your electricity rate (ensure that you factor in all the taxes and separate fuel charges, if any).

X = X / 1000.

X is now equal to 18 kWh.

At the U.S. national average electricity rate of $0.12/kWh, that heater would cost $2.16/day to operate.

To calculate how much power your heater would consume on a monthly basis, multiply X by 30. The result is 540 kWh per month. In that case, the heater would cost (540 * $0.12) $64 to run per month.

This is why space heating accounts for a whopping 41% of household energy usage! (in the United States).

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Understanding Heater Wattage

Electric heaters have two wattage ratings. One is the power consumption, and the other is the heating capacity. Advertised heater wattages are normally their power output, not their power consumption. To determine a heater’s wattage in terms of its power consumption, check the label at the back or bottom of the heater for electrical ratings.

The label may provide either a voltage and amperage, or a rating in Watts. If it’s the former, then you would calculate the heater wattage using the following equation: Watts = Volts * Amps * Power Factor. The power factor should be 1, but it isn’t necessarily that.

The efficiency of a heater is equal to the heater capacity / heater wattage * 100. The result is a percentage. This is the percentage of the power input that is converted into heat.

So, in the case of a 115 Volt, 10 Amp heater (may be written as 115VAC, 10A on the label), that would be:

115 * 10 * 1 = 1,150 Watts.

The information below is estimated. Use it at your own risk.

The Most Efficient Heaters

  1. Heat Pumps: Heat pumps can provide 3 units of heat per unit of electricity consumed.
  2. Radiators: Radiators can provide up to 1 unit of heat per unit of electricity consumed.
  3. Fan Heaters: Fan heaters can provide a little under 1 unit of heat per unit of electricity consumed, due to their fans’ power consumption.

Natural gas heaters aren’t bad either, but here’s the issue with most space heaters: They convert almost 100% of the electricity consumed into heat (with the exception of heat pumps, which can provide up to 3,000 Watts of heat for every 1,000 Watts of electricity consumed).

Despite that, the power consumption of space heaters is still very high. This means you are going to need much more than just an efficient heater to lower your electric bill. You need a solid plan, lots of silicone sealant, and great insulation.

Many homeowners have proven that you can dramatically lower your heating costs through the use of caulking and insulation. Insulation traps heat in your home. It also helps to prevent heat from getting in when the sun is beating down on your walls in the summer.

Efficiency Of Furnaces – Condensing Vs Non-Condensing Furnaces

Non-condensing gas furnaces utilize one heat exchanger (called the primary heat exchanger), which hot exhaust gases (from combustion) are passed through to heat it up. A blower circulates the air in your home over that now-warm heat exchanger to heat it up. A condensing furnace contains not only a primary heat exchanger, but a secondary one as well.

A gas-fuelled furnace.
A gas furnace being serviced.

The secondary heat exchanger absorbs the heat left over in the exhaust gases after they exit the primary heat exchanger. Both heat exchangers heat the air and serve the purpose of squeezing as much heat as possible out of the hot exhaust gases.

Non-condensing furnaces have an AFUE rating of 80%-90%, and unsurprisingly condensing furnances have a superior AFUE rating exceeding 90%. AFUE means Annual Fuel Utilization Efficiency. This is a rating system used to gauge the fuel efficiency of furnaces.

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How To Reduce Furnace Gas Consumption

You can reduce the natural gas consumption of your furnace (or oil-fired heater) with the following tricks:

Insulation: Insulation is a material that impedes the transfer of heat. A well-insulated house requires far less energy to maintain your thermostat temperature because it traps the heat generated by your heater for a longer time. Inversely, a poorly insulated (or uninsulated) house will let the heat escape through the walls. This means that your HVAC system will have to generate more heat to compensate for that loss, resulting in a higher fuel oil consumption (or equally increased natural gas consumption in the case of gas-powered furnaces).

Sealing/Caulking Air Leaks: Due to the effects of pressure gradient force and convection, heat can leak out through cracks and other holes in windows and doors.

Setting A Lower Thermostat Temperature: Thermostat temperature has a significant effect on a furnace’s fuel usage, therefore, try not to set it any warmer than necessary. If you find more comfortable, warmer clothing, you can make do with a lower thermostat temperature.

Heat Pumps Vs Fan Heaters

Heat pumps utilize the vapour compression technology that air conditioners use to harvest heat from the outside air and use it to heat your home. A heat pump is an air conditioner that operates in reverse (in the context of space heating), transferring outdoor heat inside as opposed to pumping indoor heat outside. Heat pumps raise the energy efficiency bar to a level unattainable by other heaters because other heaters are only capable of converting their energy sources to heat, while heat pumps can make use of existing heat.

For example: A fan heater consuming 1,500 Watts cannot provide more than 1,500 watts of heat (5,118 BTU). To make it easier to relate fan heater heat output to heat pump output, 1 Watt of heat is equal to 3.412 BTU. Heater wattage directly correlates with BTUs, as the Watt and the BTU are interchangeable units.

However, a heat pump consuming 1,500 watts (depending on the model) could provide 15,000 BTU (depending on the model). If you’re maintaining an uncomfortably low thermostat temperature due to high energy costs, then a heat pump may be helpful, considering the following.

The Cost Of Heat Pumps

Heat pumps contain one or more compressors, often two fans, two heat exchangers which must be cleaned regularly, some may contain compressor crankcase heaters, filters, among other parts that need to be maintained or replaced. Combined with the high initial cost of heat pumps (for example: $1,000 for a 2.6 kW heat pump vs $100-$200 for a 3 kW fan heater), a heat pump’s cost of ownership isn’t exactly low.

A heat pump may not work in some (extremely cold) climates, therefore a backup heater may be required. Many heat pumps come with auxiliary heating elements, just in case you end up in such a situation.

Bear in mind that the auxiliary heating elements consume just as much power as the cheap fan heaters mentioned above do. The percentage of time that the temperature in your climate falls below that of a given heat pump’s minimum operating temperature will help you determine the most financially viable option.

The cost to run a heat pump is dependent on the climate it is in, but in most cases, it is 1/3 of a conventional electric heater.

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Comparing Fan Heater Ratings Vs Heat Pump Ratings

  • 1,000 Watts: 3,412 BTU.
  • 1,500 Watts: 5,118 BTU.
  • 3,000 Watts: 10,238 BTU.

Conversion Of BTU To Watts (Heating Capacity)

9,000 BTU = 2,637 Watts (2.6 kW).

12,000 BTU = 3,500 Watts (3.5 kW).

18,000 BTU = 5,215 Watts (5.2 kW).

20,000 BTU = 5,861 Watts (5.8 kW).

24,000 BTU = 7,033 Watts (7 kW).

28,000 BTU = 8,206 Watts (8.2 kW).

30,000 BTU = 8,792 Watts (8.8 kW).

36,000 BTU = 10,550 Watts (10.5 kW).

40,000 BTU = 11,723 Watts (11.7 kW).

48,000 BTU = 14,067 Watts (14 kW).

Reverse Cycle Air Conditioners Vs ‘Electric Heat’

One important fact is the difference between reverse cycle air conditioners (the ones with heat pump capabilities) and air conditioners that just contain an electric heating element. Many units carry labels such as ‘with electric heat’, or sellers may say that they ‘heat/cool’. Some of these units are not reverse cycle, and will therefore consume three times more electricity than reverse cycle units/heat pumps.

Always look for ‘heat pump’ or ‘reverse cycle’ when shopping for an air conditioner that provides heat, unless you rarely need heating or live in a climate in which the unit cannot operate. Heat pumps do have temperature limitations. You should also get a heat pump with an auxiliary heater/supplemental heat, as these can back you up during periods of unusually cold weather.

Before you proceed, please note that when I say a unit is ‘on’ below, i’m referring to the compressor. Not how long you leave the heater running. Heaters cycle their compressors or heating elements on and off depending on the temperature to ensure that they maintain the thermostat temperature, set by you.  

Power Consumption Of Heaters By Size

VRF: Variable Refrigerant Flow.

Inverter: Variable Refrigerant Flow/Variable Speed Compressor.

Heat Pump: Reverse-cycle Air Conditioner.

Inverter: Variable Refrigerant Flow/Variable Speed Compressor.

Power Consumption Of 9,000 BTU Heaters (Heat Pumps)

The wattage of one of the sample 9,000 BTU heaters viewed was 720 watts (0.72 kW). It provides 3.6 units of heat for every unit of electricity it consumes.

The power consumption of the two sample heaters analysed ranged from 720 watts to 890 watts. The 720 watt unit provides 3.6 units of heat per unit of electricity consumed, and the 890 watt (0.89 kW) unit provides 2.9.

Energy cost of the 720 Watt unit: $0.0864 per hour. If you ran it for 12 hours per day, it would cost approximately $1.03 per day, assuming a U.S. electricity rate of $0.12/kWh.

Monthly cost of running a 9,000 BTU heater assuming the variables above:


Multiply that by 3 to estimate the cost of a conventional fan heater (with the same usage pattern) and your result is: $93.

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Power Consumption Of 12,000 BTU Heaters (Heat Pumps)

The power consumption of 12,000 BTU heaters viewed ranges from 0.76 kW (Panasonic 12,600 BTU CS/CU-Z12RKR) to 1.17 kW (12,000 BTU Senville SENL-12CD). Both the Panasonic and Senville units were of the inverter variety. The Panasonic provides 4.85 units of heat per unit of electricity consumed, and the Senville unit provides 3. Therefore, the cost to run this 12,000 BTU heat pump under those circumstances is:

A national average energy cost of $0.12 USD/kWh is assumed, rates vary with location.

Energy cost of the 1.17 kW unit per hour of usage: $0.1404.

Energy cost of the 1.17 kW unit per month if it is used for 12 hours per day:


You can multiply that by 3 to estimate how much it would cost to run a conventional fan heater or radiator, and your result would be: $151.

Power Consumption Of 24,000 BTU Heaters (Heat Pumps)

The power consumption of 24,000 BTU heaters viewed ranges from 2,000 watts to 2,500 watts. The 2,000 watt model was not an inverter/variable refrigerant flow unit and provides 3.5 units of heat per unit of electricity consumed (a more convenient way to look at it is 3,500 watts of heat for every 1,000 watts of power it consumes).

The 2,500 watt model was of the inverter/VRF variety and provides 2.81 units of heat for each unit of electricity consumed. This does not mean that inverter air conditioners consume more power. This Ramsond model just happens to be more efficient.

2,000 watt unit: Ramsond 74GW3.

2,500 watt unit: Senville SENA-24HF-Z.

Operational cost of the 24,000 BTU heat pump assuming a 50% duty cycle (12-hour/day operation):

720 kWh per month – $86.

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