Baseboard Heater Sizing (120V vs 240V)

Baseboard heaters are long modular units that fit wall trims beneath windows. Baseboards work through passive convection by pulling in the cold air. Then, the unit heats the cold air and releases it as warm air into the room.

Baseboard heaters use zone heating. This means they heat one room at a time, allowing each room to have its own temperature control.

When looking for popular baseboard sizes, knowing the square footage of your room is very helpful. Knowing this value helps you find the size of the baseboard you need for proper heat output.

If you are looking for electric baseboard heating, you might wonder "What size baseboard heater do I need?" To answer this you need to know how to size a baseboard heater.

Sizing a baseboard heater is a simple task that you can complete in 3 easy steps.

Sizing a baseboard heater watts per square foot:

1. Measure the room: Length (L) x Width (W) = Square Footage
2. Multiply by 10 watts (with good insulation): Square Footage x 10 = Target watts
3. Adjust for ceiling heights over 8ft, poor insulation, or if the heater is the main source of heat
• If the room is taller than 8 feet:
• Add 25% if the ceiling is 10 ft tall
• Add 50% if the ceiling is 12 ft tall
• In an older homes, multiply square footage by 12.5 watts
• In ultra-insulated homes, multiply square footage by 7.5 watts

If you are unsure about the calculation, use a baseboard heater size calculator service instead. Or, use a baseboard heater wattage chart (pictured below):

Baseboard heaters tend to have two main voltages that they operate at. These voltages are: 120V and 240V.

120 Volt Baseboard Heaters

120V baseboard heaters are great for smaller rooms and on shorter runs. 120V baseboards are convenient in many homes as they can match existing 120V circuits and thermostat lines. 120V heaters normally connect to a single-pole circuit breaker.

Disclaimer: If you are not a licensed electrician, do not participate in any wiring installation. Instead, call a local licensed electrician to help you with your wiring.

240 Volt Baseboard Heaters

240V supports higher output on a smaller breaker amp draw. This means 240V baseboards can handle longer runs using fewer circuits. However, they offer the same energy per watt-hour as 120V baseboards.

These heaters are the standard for higher-wattage heaters and require a two-pole circuit breaker.

While both of these heaters are a great option to choose from, it is important to keep in mind a few things.

1. When purchasing a new heater, ensure it aligns with the current circuits voltage.
2. Do not connect 120Vs to 240Vs outlets. Do not to connect 240Vs to 120Vs outlets.
3. Discuss potential wiring changes with an electrician to keep with the codes in your area.

The two main types of baseboard heaters are electric and hydronic. Both types of heaters mount to the floor and distribute heat. However, there are some differences that set them apart.

Electric Baseboard Heaters

These heaters use electric heating to generate heat inside the unit. The element heats up and warms the air in the room. They are a typically cheaper option than hydronic heaters, featuring a lowering upfront cost. However, they may have a higher energy consumption cost.

Hydronic Baseboard Heaters

Hydronic heaters are hot water baseboard heaters that circulate hot water or other fluids through the unit's pipes. Then, a boiler heats the water and a circulating pump pushes the heated water through the system.

Hydronic heaters are more energy efficient than electric baseboards and produce more consistent heat.

Determining the sizing of a hydronic baseboard heater is a bit different than electric baseboards. You must size hydronic units by BTUS, so a different formula is needed. To determine the size of the baseboard heater, follow these steps:

1. Measure the room: Length (L) x Width (W) = Square Footage
2. Multiply by BTUs: Square Feet x 34 BTUs = Total BTUs
3. Find the linear foot of the baseboard: Total BTUs / 600 = Size of the baseboard

For more information about Electric and Hydronic baseboard heaters, read our blog here.

Baseboard heaters are typically found in either 120V or 240V. However, if you are looking for a more efficient baseboard, choose from a variety of 240V baseboards today at HomElectrical!

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