How Many Watts of Baseboard Heat Do I Need? Size and Feet by Room
Part of the project planner: Planning heating, cooling and ventilation.
The usual rule is 10 watts of baseboard heat per square foot for a room with an 8 foot ceiling and average insulation. A 14 × 12 ft room needs 1,680 watts (5,732 BTU per hour), which is 6.7 ft of baseboard at 250 watts per foot, 7 amps at 240 volts and a 15 amp breaker. The baseboard heater size calculator does your own room.
Baseboard heat by room size
Average insulation (10 W per ft²), 8 ft ceiling, 240 V, 250 W per foot:
| Room | Area | Watts | Baseboard | Amps | Breaker |
|---|---|---|---|---|---|
| 8 × 8 ft | 64 ft² | 640 W | 2.6 ft | 2.7 A | 15 A |
| 10 × 10 ft | 100 ft² | 1,000 W | 4.0 ft | 4.2 A | 15 A |
| 10 × 12 ft | 120 ft² | 1,200 W | 4.8 ft | 5.0 A | 15 A |
| 12 × 12 ft | 144 ft² | 1,440 W | 5.8 ft | 6.0 A | 15 A |
| 12 × 16 ft | 192 ft² | 1,920 W | 7.7 ft | 8.0 A | 15 A |
| 14 × 14 ft | 196 ft² | 1,960 W | 7.8 ft | 8.2 A | 15 A |
| 16 × 20 ft | 320 ft² | 3,200 W | 12.8 ft | 13.3 A | 20 A |
| 20 × 20 ft | 400 ft² | 4,000 W | 16.0 ft | 16.7 A | 25 A |
How insulation changes it
For the 14 × 12 ft room:
| Watts per ft² | Watts needed | Baseboard | Amps at 240 V |
|---|---|---|---|
| 8 W per ft² | 1,344 W | 5.4 ft | 5.6 A |
| 10 W per ft² | 1,680 W | 6.7 ft | 7.0 A |
| 12 W per ft² | 2,016 W | 8.1 ft | 8.4 A |
| 15 W per ft² | 2,520 W | 10.1 ft | 10.5 A |
Use 8 W per ft² for a well-insulated room in a mild climate, 10 for average, 12 for an older or poorly insulated room, and 15 for a cold, drafty room or one over a garage. A higher ceiling scales it up: a 10 ft ceiling needs 25% more.
Choosing heaters
- Spread the heat. Put the heaters along the outside walls and under the windows. Several short heaters heat a room more evenly than a single long one.
- Pick the voltage. 240 V heaters draw half the current of 120 V heaters of the same power, so they need smaller wires and breakers.
- Use a thermostat in every room rated for the load.
- Check the circuit. Add up all the heaters on one breaker: the total must not exceed 80% of its rating. See the circuit capacity calculator.
- Leave clearance. Keep curtains and furniture away from the heater.
Is it the best choice?
Electric baseboard is cheap to install and quiet, and it controls each room separately. But it is expensive to run where electricity costs a lot: compare it with other fuels in the heating cost comparison, or consider a ductless heat pump, which gives two to four times as much heat per kWh. For a small room, a portable heater may do (see the space heater size calculator).
Electrical work can start fires: follow your local code, and have a licensed electrician install the circuit. Estimates only.
Frequently asked questions
How many watts of baseboard heat do I need per square foot?
About 10 watts per square foot for a room with an 8 foot ceiling and average insulation: 1,680 watts for a 14 × 12 ft room.
How many feet of baseboard heater do I need?
At 250 watts per foot, 6.7 ft for a 14 × 12 ft room, and 16 ft for a 20 × 20 ft room.
What breaker do I need for a baseboard heater?
15 amps at 240 V for 1,680 W, since a heater is a continuous load, rated at 125% of its current. The same load on 120 V draws 14.0 amps and needs a 20 amp breaker.
Is baseboard heat expensive to run?
It gives one kWh of heat for each kWh of electricity. The 1.7 kW for this room costs 1.7 times your price per kWh for every hour at full output, which is two to four times what a heat pump costs.
Where should baseboard heaters go?
Under windows and along outside walls, with a thermostat in each room and nothing blocking the heater.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.