Most space heaters use 1500 watts of electricity per hour.
However, there are smaller heaters too, starting at 200W per hour.
This guide discusses space heater electricity usage and answers other questions:
How Much Electricity Does a Space Heater Use?
The watt rating of your space heater is how many watts of electricity it uses per hour.
You have options for units with one heat setting and those with multiple heat settings.
Single-setting space heaters are usually 1500W, but you’ll find smaller ones from 200W to 1000W power.
There are heaters with 2000W and 4000W of power, but they’re not as common and don’t fit our notion of a space heater. Most are used for larger spaces. For example, see our Best Garage Space Heater Guide for options.
When units have multiple heat settings, the most common are:
- 750W & 1500W
- 1000W & 1500W
- 500W, 1000W & 1500W
Again, remember that those settings are electricity consumption per hour. We turn those numbers into costs below.
If you’re not sure what size you need, our comprehensive Garage Heater Size Calculator is a good source of information.
How Much Space Does a Space Heater Heat?
Sounds like the old tongue-twister – How much wood would a woodchuck chuck…
It turns out, there are many factors to consider when sizing a space heater. But we’ll assume two:
- Supplemental heat: The room is heated, but inadequately, so you want to boost heat by up to 10 degrees Fahrenheit.
- Insulated space: The space is enclosed and insulated, so heat isn’t rapidly leaking from it.
As a general rule, you need 10 watts per square foot for supplemental heating. Here’s what that looks like:
- 500 watts: Up to 50 square feet (5×10, 7×7) – Bathroom, cubicle, desktop and other personal uses
- 750 watts: Up to 75 square feet (7.5×10, 8×9) – Bathroom, small office or small bedroom
- 1000 watts: Up to 100 square feet (10×10, 12×8) – Large bathroom, den, office, small bedroom, galley kitchen or dorm room
- 1500 watts: Up to 150 square feet (10×15, 12×12) – Bedroom, office, kitchen, small living room
By the way, if you’re comparing electrical heat to gas heat – whether a gas space heater or your home’s furnace – here’s the conversion rate:
- 1 watt = 3.4 BTUs per hour.
- 500W = 1,700 BTU/h
- 1000W = 3,400 BTU/h
- 1500W = 5,100 BTU/h
As you can see, it would take a massive space heater to put out as much heat as an average-sized gas furnace.
29,411W = 100,000 BTU/h
Electric furnaces are really just massive electrical heaters working with a blower fan to disperse heat throughout a home.
Convection Heat vs Infrared Heat
There’s another wrinkle to consider – the type of heater being used.
Convection heaters heat the air. Many are ceramic space heaters, but some are bare metal coil types. They have an element that gets hot, and the heat is dispersed with natural airflow or with the assistance of a fan.
Infrared space heaters heat people and objects. They use infrared radiation, which is directly absorbed by the objects in its path. Infrared is perfectly safe. It’s the kind of heat the sun gives off. On a cool spring day, you might need a jacket in the shade. But step into the sunlight, and you’ll immediately warm up.
Here’s the question again: How much space does a space heater heat?
The real answer is, “It depends on what type of heater you are using.”
Convection heaters: The 10 watts per square foot applies to this type of heater.
Infrared: Because the technology directly heats objects, it’s more about proximity to the objects. Most are rated to heat people up to 10 or 15 feet away. The 10W/S.F. rule doesn’t apply. You’ll sometimes see infrared space heaters rated for “up to 1,000 square feet,” but that’s misleading.
Convert Watts to Kilowatts
This is the first step in figuring out how much electricity is used by a space heater and how much it costs to run one.
The conversion is helpful because most energy companies charge by the kilowatt hour, or kWh, of electricity used.
The conversion is simple: 1000 watts = 1 kilowatt
A 1500W space heater uses 1.5 kilowatts of electricity per hour, or 1.5 kWh.
How to Determine the Cost of Electricity
The next step is to view your energy bill. The price of electricity will be listed per kWh.
Your bill will have a section called Electric Charges
It will show the number of kilowatt hours, the rate charged per hour and the amount billed. It will look something like this:
- 90.275 * 0.139125=$12.56
That equation is 90.275 kilowatt hours (kWh) multiplied by 13.9125 cents per kWh equals $12.56 charged to your bill.
Some energy companies have different rates for time of day during the summer months.
For example, Consumers Energy has a summer Peak Rate from 2pm to 7pm when most air conditioners are in use. The Off Peak Rate applies the rest of the day.
In such cases, your bill will look something like this:
- On-Peak Energy 111.410* 0.143752=$16.02
- Off-Peak Energy 402.749* 0.096781=$38.98
Energy consultant group Electric Choice tracks electrical rates across the US. It says that the current average cost is 13.9 cents per kWh, or kilowatt hour.
The page also lists average costs by state. They vary dramatically from less than 10 cents per kWh in states like Arkansas and Louisiana to more than 20 cents in Alaska and the New England states to more than 30 cents per kWh in Hawaii. Most states have electric rates from 11 to 17 cents per kWh.
How Much Does it Cost to Run a Space Heater?
This table shows the Cost Per Hour of running a space heater. You can plug in your own electric rate, of course, and do the math.
|Heater Size||@10 cents||@15 cents||@20 cents||@30 cents|
|200 watts||2 cents||3 cents||4 cents||6 cents|
|500 watts||5 cents||7.5 cents||10 cents||15 cents|
|750 watts||7.5 cents||11.25 cents||15 cents||22.5 cents|
|1000 watts||10 cents||15 cents||20 cents||30 cents|
|1500 watts||15 cents||22.5 cents||30 cents||45 cents|
*A space heater fan uses about 5 watts per hour, so makes little difference in space heater operating cost.
How to Reduce Use a Space Heater Efficiently
This section could be titled, How Not to Waste Electricity with a Space Heater.
These tips will help you stay warm without the waste.
1. Size your space heater properly. Remember the 10W per square foot rule (or see the chart above). It’s easy to waste heat with a space heater that is too big for the room.
2.Buy a unit with energy-efficient features.
- Timer: Ensures the heater will turn off if you forget to.
- Digital thermostat: Set the heat to a temperature that keeps you warm without overheating the space and wasting energy.
- Economy mode: Usually called Eco mode, it means that a space heater with two heat settings will automatically shift to the lower setting once the thermostat setpoint has been reached. If the room cools off, the heater will switch back to the higher setting.
3. Wear warmer clothing. A base layer (long underwear is what it was once called), sweater, warm slippers and other gear can keep you warm without a space heater or with the heater on a lower setting.
4. Home upgrades make your entire house more energy efficient.
We have covered the last point in great detail in our Most Efficient Space Heater Guide.
First is a list of the most efficient space heaters. At the end of the guide is a detailed section on making your home efficient. It includes small things like using weather stripping on draughty doors and windows, medium projects like adding attic insulation to major renovations like new energy-efficient windows and roofing material.