How to Install a 240-Volt Electric Baseboard Heater

Bob Formisano is a licensed architect and builder with nearly 40 years of experience building new homes and restoring older homes. One of his specialties is repairing old systems dating back to the 1920s, including galvanized water pipes, knob-and-tube wiring, and more. His home repair articles for The Spruce span more than 10 years.

Larry Campbell is an electrical contractor with 36 years of experience in residential and light commercial electrical wiring. He worked as an electronic technician and later as an engineer for the IBM Corp. He is also a member of The Spruce Home Improvement Review Board.

Sarah Scott is a fact-checker and researcher who has worked in the custom home building industry in sales, marketing, and design.

• Total Time: 3 hrs

• Skill Level: Advanced
• Estimated Cost: $75 to $450

Electric baseboard heaters provide radiant heat, using natural convection (hot air rises, cold air drops) to circulate heat into a room. In some climates, baseboard heating can provide all the heat required by a home, but it is more common for baseboard heating to provide supplemental heat for spaces where the central HVAC system is insufficient. For example, extending the central forced-air heating system to heat the space can be challenging in a basement or attic room conversion, and electric baseboard heaters offer an easy way to serve those areas.

Electric baseboard heaters use their own circuit. Electric baseboard heaters can be powered by either a 120-volt or 240-volt circuit. Electricians generally install 240-volt heaters since they use lower amperage and are more energy-efficient than 120-volt heaters. Adding a 240-volt baseboard heater usually requires a new 20- or 30-amp double-pole circuit breaker and new circuit wiring to supply one or more heater units.

If your baseboard heater unit fails, you can replace it on your own, depending on if the new baseboard heater plugs in easily to the old unit. However, if the wiring to your old heater is the problem, you might need an electrician to handle the more advanced work of fixing the wiring. If you only need to change the baseboard cover, it's easy enough to change in a few minutes without tools by removing the end caps and front cover and replacing them.

Warning

Installation of a circuit and heater is an advanced home wiring project usually done by a licensed electrician or heating contractor. DIYers should have considerable wiring experience before attempting this project since it involves running electrical cables and installing and connecting a new circuit breaker in the main service panel.

How Much Does It Cost to Install Electric Baseboard Heaters?

Each baseboard heater—the part only—can be $50 to $250 apiece. When a professional electrician installs it, expect to pay at least $75 to $175 per hour. On average, budget at least $500 per unit you have installed. If you do it yourself, depending on the unit you get, it can cost you significantly less to install an electric baseboard system on your own.

Choosing a Heater Size

Baseboard heaters come in many sizes to match the heating needs of the room. The rating or heating capacity of a baseboard heater is commonly measured in wattage, which is governed by the length of the heater. A common rule of thumb is to provide 10 watts of heat for every square foot of space in the room. However, this may vary somewhat depending on the configuration of the room and details such as ceiling height, wall insulation, number of windows, and other factors.

Baseboard heaters typically come in standard lengths, from 24 to 96 inches. A 240-volt 24-inch heater generally is rated for about 350 watts (enough for a small bathroom), while a 96-inch heater is rated for 2,000 to 2,500 watts (enough for a 200- to 300-square-foot space). You can also meet heating needs with two or more heaters that combine to provide adequate heating.

While wattage is commonly used to measure heating capacity, the actual output of a heater is measured in BTUs (British thermal units). The BTU rating can be helpful when comparing electric heater size to other heaters or heating equipment types.

Placement of a Heater and Thermostat

The best location for an electric baseboard heater is under or near windows to take advantage of natural convection currents in the room and to offset the heat loss through the glass. Building codes caution against or do not allow baseboard heaters to be installed beneath electrical wall outlets. Also, as the codes point out, it is not safe to wire a baseboard heater to an electrical outlet because you can increase the chance of blowing a fuse or wires catching fire.

Electric baseboard heaters require a minimum of 1 inch of air space under the unit for the convective airflow to work correctly. They also should have at least 12 inches of clearance from window coverings and furniture.

Thermostats for baseboard heaters can go anywhere in the room but tend to give the most accurate reading when located on an interior wall and away from other heat sources. They are typically mounted slightly higher than the typical wall switch. Some baseboard heaters have thermostat units built into the heaters and require no wall thermostat.

How to Install a 240-Volt Electric Baseboard Heater

What You'll Need

Equipment / Tools

• Drywall saw
• Cable fish tape (if needed)
• Drill and bits
• Wire strippers
• Stud finder
• Torpedo level
• Screwdrivers

Materials

• Electrical wall box
• NM electrical cable
• Double-pole line-voltage thermostat
• 240-volt electric baseboard heater
• 1/2-inch cable clamp
• 1 1/2-inch drywall screws
• Wire connectors
• Black electrical tape
• 240-volt circuit breaker

Instructions

Install a Wall Box for the Thermostat

Make a cutout for the line-voltage thermostat and install a wall box. A standard "old work" (retrofit) switch box works well on finished walls. You can cut the hole for the box with a simple drywall saw but wait to install the box until the wires are pulled. (If this is new work, you will not cut drywall.) At the location of the baseboard heater, you will also need to make a hole in the wall where the electrical cable will extend out from the wall and into the heater's wire connection panel.

Run Cable for the Circuit

Run two lengths of NM cable—one from the main service panel to the thermostat location and another cable from the thermostat to the baseboard heater location. No wall box is generally required at the heater location since the wire connection panel on the heater serves as an approved box. Running cable through finished walls can be tricky, requiring saws, a drill, and electrical cable fish tape.

Tip

A 240-volt baseboard heater requires its own dedicated 20-amp or 30-amp 240-volt electrical circuit. A 20-amp circuit can safely provide 3,800 watts of power, while a 30-amp circuit is suitable for up to 5,700 watts. The standard circuit cable for 20-amp circuits is 12-gauge; 30-amp circuits need a 10-gauge cable. The circuit cable is typically a two-wire cable with ground, where the black and white wires serve as hot wires. When using the white wire as a hot wire, as in this project, you must place red or black tape on the white wire to indicate that it is hot.

Mount the Baseboard Heater

The basic steps of installing a baseboard heater unit are relatively standard: Remove the knockout on the back of the heater's connector box and install a 1/2-inch cable clamp to the box. Feed the circuit cable through the cable clamp and into the wire connection panel on the baseboard heater, leaving 6 to 8 inches of extra cable extending beyond the clamp. Remove all but 1/2 inch of the cable sheathing inside the connection panel, then strip 1/2 inch of insulation from the end of each conducting wire in the cable. Tighten the cable clamp onto the cable. Use a stud finder to locate wall studs behind the baseboard heater. Fasten the heater to at least two wall studs using one 5/8-inch drywall screw. Use a torpedo level to level the unit if it is a type that is not floor-mounted. If you have a floor-mounted unit, you may have to cut out the baseboard where the heater goes to fit the unit against the wall.

Make the Wire Connections at the Heater

Look in the connection box for the factory wiring connection on the unit's heating element. Following the manufacturer's instructions, disconnect the wire connector (wire nut) that holds the connection together. Connect one factory wire to a hot power wire from the 240-volt circuit cable, and connect the other factory wire to the second hot power wire from the circuit cable. Note that in a standard 240-volt circuit, the black and white wires serve as hot wires since there is no neutral wire. Mark the white wire with a band of black electrical tape to indicate that it is a hot wire. Connect the bare copper grounding wire to the green grounding screw in the heater connection box. Install the connection panel cover.

Make the Wire Connections at the Thermostat

Strip about 3/4 inch of insulation from each conducting wire from both cables in the thermostat box. Following the thermostat manufacturer's directions, connect the wire leads marked "line" to the wires entering the box from the service panel. Connect the wire leads labeled "load" to the wires running to the baseboard heater. Be sure to place a piece of black or red tape to identify the white wire as hot. The bare copper grounding wires in the box should be joined with a wire connector. If the wall box is metal, it should also be grounded by a grounding pigtail wire. Tuck the wires into the box, secure the thermostat to the box with mounting screws, and attach the cover plate.

Tip

Connections vary considerably among manufacturers, so read the thermostat directions when making these connections.

Connect the Circuit Breaker

The last step to finishing the installation is to connect and install the 240-volt circuit breaker in the main service panel. This involves first shutting off the main breaker and opening up the panel. Then, you connect the new circuit's ground wire to the panel's grounding bar and connect the black and white circuit wires to the screw terminal connections on the circuit breaker. Snap the circuit breaker into an empty slot in the service panel. Finish by closing up the panel and turning on the main breaker. Be sure to mark the panel index to identify the heater breaker. You must also mark the white wire again with red or black tape to indicate that it is hot.

Warning

Working in the main service panel is risky if you are not experienced. Never work inside a panel if you are unfamiliar with its parts and how to avoid shock. You must turn off the main breaker before working in the panel, but even with the main breaker off, there are elements in the panel that carry deadly currents at all times.

Test the Heater

Turn on the circuit breaker controlling the heater circuit. Test the heater by turning the thermostat up to a high temperature to make sure the heater produces heat and responds accurately to the thermostat settings. Then turn the thermostat off and make sure the heater shuts off.

Tip

Baseboard heaters are often shipped with a protective coating on the heat fins. The first couple of times you operate the heater, there may be an odd smell, and it may also set off smoke detectors. The protective coating should dissipate after a few uses.

Electric baseboard heaters are not the most heat-efficient devices; they use more electricity than an electric heat pump and cost more in electric bills. Unfortunately, they also take up wall space and make furniture placement difficult since everything needs to be at least 12 inches away. They also generate dry heat, usually requiring a supplemental humidifier to offset the dryness. They can get hot to the touch, which can be problematic with the elderly, young children and pets in the house.

Yes, you can leave baseboard heaters on all the time. They are generally considered safe as long as they have a thermostat that can shut the unit off once it reaches a specific temperature. Also, do not keep any objects near the unit, like hanging curtains or things that can impede airflow or act as a fire hazard.

Electric baseboard heaters are less costly to install but use more energy in the long run, costing more to heat your home than most all other heat sources, such as propane, oil, natural gas, or a heat pump. Hydronic baseboard heating is also less of an energy expense than electric baseboard heating.

Cold drafts assist in the convection process. The cool air from the window mixes with warm air rising out of the baseboard; that warm air moves around the room cools, and sinks back to the floor to be re-heated by the baseboard heater.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. Fixed Electric Space Heating Equipment: 424.9. National Electric Code 2020 of Illinois.
2. Home Wiring Hazards. United States Consumer Safety Commission.
3. As Temperatures Go Down, The Chance for Injury from Heaters Goes Up. Vanderbilt University Medical Center.
4. Fire Prevention Month: Heating Safety. City of Seattle Fire Department.
5. Heating and Cooling. Energy Saver, Vermont Department of Public Service.