How to Calculate Total Wattage of Baseboard Heaters

Electric baseboard heaters are often the easiest and most efficient way to add heat to a room or convert an unheated space, such as an attic or basement, into a living space. But if you wonder how to precisely calculate the total wattage of baseboard heaters in each room in your house, you don’t have to worry. There is a simple formula you can use to get the total wattage of your heaters. So let’s start!

How to Calculate Total Wattage of Baseboard Heaters

So How to Calculate Total Wattage of Baseboard Heaters? The best way to calculate the total wattage of baseboard heaters is to measure each heater individually and add them up together. Electric baseboard heaters on average have 225 watts per foot. To get heaters wattage you need to measure the length of the heater and multiply it by 225. Add up each heater individually to get total wattage.

Example: Heater 1, Length (feet) x 225 Watt; Total Wattage: Heater 1 + Heater 2 + Heater (n)

The thing to pay attention to is that most smart thermostats have a limit, and can handle up to 3,800W on one circuit. Therefore, be careful not to exceed this wattage. The number of baseboard heaters that can be safely wired to one thermostat depends on what type of wiring you have, the size of the breaker in the electrical box, and the total wattage of every individual heater.

You can look for some amazing baseboard heaters here on Amazon.

Let’s take a look at some of the methods you can use to calculate the total wattage of baseboard heaters:

Method 1: Look For Manufacturer’s Label

The best and easiest way to calculate the total wattage of baseboard heaters in your home is to check for the manufacturer’s label on your heaters. There should be a sticker with the listed wattage number. Use that value. If there is no wattage number on it, and the label lists only voltage and amperes but no watts, you can easily determine the correct wattage of each heater with the following formula:

W=A x V

Watts= Amps x Volts

Example: 2,1A x 240V = 500W

If you use this formula, you should get an exact number of Watts as on the sticker on your heater.

Method 2: Measure the Length of the Heater

If there is a manufacturer’s label, but you are unable to read it or it is missing, then you can calculate the wattage for each baseboard heater by measuring its length. On average, electric baseboard heaters have 225 watts per foot (1 ft= 30 cm). To approximate the heater’s wattage, use the following formula:

L x 225 ≈ W

Length (Feet/Meters) x 225 ≈ Watts

Example: 4.5 ft x 225 ≈ 1,000W

Note: Keep in mind that this is an estimated value, not a correct value. Therefore, make sure that if your calculation approaches the value of around the 3,800W limit, contact the professional to see if everything is compatible.

Total Wattage: Add Up All The Heaters

Pay attention that total wattage must include every baseboard heater that is attached to a single thermostat. To do this, just calculate the wattage of each baseboard heater and at the end add them all together.

Heater 1 + Heater 2 + Heater 3 < 3,800W

Once you’re done with the calculation, if you’re under 3,800W, you will not have any problems!

Related Article: How to Set Thermostat to Save Money? 5 Useful Tips

Calculate How Much Wattages You Need For a Room

First thing is to figure out what wattage you need to heat the room. To do that, you need to multiply the length and width in feet to get the floor area in square feet. Now multiple the floor area with 10 and you will get the heater wattage that is needed for that room.

Example: If room 10-by-10 feet has a floor area of 100 square feet. Multiple 100 x 10 and you will get 1,000 Watts. With this calculation, you will get the electric baseboard heater power that is needed to heat the room.

This means that you need to buy a single 1,000-watt baseboard heater or two 500-watt heaters.

To check how many Watts you have, you can use one of the following methods:

If you have a 240-volt circuit that is running on a 20-amp double-pole breaker, you can have a combination of baseboard heaters up to 3,840 watts.

Example of how many baseboard heaters you can have with just one thermostat:

  • Two baseboard heaters with 1,500 watts,
  • Three baseboard heaters with 1,000 watts,
  • Five baseboard heaters with 750 watts.

Things Needed:

Basics of Baseboard Heaters

Baseboard heaters are most commonly mounted at the bottom of the walls in the room, and they are powered by electrical circuits through wiring. While there are portable baseboard heaters that can be plugged into standard wall outlets, it is best to use them temporarily only; for permanent heating, it is best to install permanent baseboard heaters and attached them to the wall.

Permanent heaters are available in 120 volts and 240 volts versions. My recommendation is to install the 240-volt heaters, as they are way more efficient when it comes to heating and energy use.

When you buy baseboard heaters, you may notice many different specifications, such as the length of the baseboard heater, its wattage, voltage, and amperage. In order to choose the right heaters that are sufficient for the space you need to heat, the wattage rating is most critical. Keep in mind that longer baseboard heaters produce more power (wattage).

Example from one Baseboard heater manufacturer: 

240-Volt Baseboard HeaterWattages:
30 inches500 watts
36 inches750 watts
48 inches1,000 watts
72 inches1,500 watts

Recommended Heating Requirements For Room

It is therefore always preferable to choose slightly oversized baseboard heaters. There is no loss of efficiency when heating with baseboard heaters slightly above the minimum requirements.

Total Area of RoomRecommended Heater RatingElectric Circuit Size (240V)
100 square feet900 watts15 amps
150 square feet1,350 watts15 amps
200 square feet1,800 watts15 amps
300 square feet2,700 watts15 amps
400 square feet3,600 watts20 amps

Final Thoughts

Now that you know how you can properly calculate the total wattage of baseboard heaters, it is time to do it yourself. As you could see, with a very simple formula in a few minutes you can get the right information about wattage for your baseboard heater. You also need to pay attention to the fact that you can have a maximum of 3,800W installed per one thermostat. We have already explained this whole procedure in the article above. If you have any more questions, feel free to write below in the comments.

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