What you need to do before you start

Replacing an electric baseboard heater is a job you can do yourself if you are comfortable working with electrical wiring, but it requires turning off power at the breaker and confirming the circuit is dead before you touch anything. The heater itself is usually held to the wall with brackets and connected to the wall wiring through a terminal block or direct wire connection. Most replacements take two to four hours, depending on whether you are reusing the existing brackets and whether the new unit is the same length as the old one.

The first step is to measure your old heater — length, height, and depth — and check the wattage and voltage on the nameplate. You will need these numbers to order a replacement that fits the space and works with your home's electrical system. Most baseboard heaters are 240 volts and range from 500 to 2,000 watts. If you are unsure about any part of the electrical work, hire a licensed electrician; the cost of a professional installation is usually $200 to $400 and is worth it to avoid a fire or shock hazard.

Key Takeaways

  • Turn off power at the breaker and test the heater with a non-contact voltage tester to confirm there is no current before you disconnect anything.
  • Measure the length, height, and depth of your old heater and note the wattage and voltage from the nameplate so you can order the correct replacement.
  • Most baseboard heaters bolt to the wall with brackets and connect to the wall wiring through a terminal block; you can reuse the brackets if the new heater is the same size.
  • If the new heater is a different length, you may need to reroute or extend the electrical wire, which requires turning off the breaker and working carefully to avoid damaging the wire insulation.
  • After installation, test the heater by turning the breaker back on and checking that it warms up within a few minutes; if it does not, turn the breaker off and check your wire connections.

Turning off power and removing the old heater

Go to your electrical panel and find the breaker that controls the baseboard heater. The breaker should be labeled, but if it is not, you can turn off breakers one at a time and have someone test the heater until you find the right one. Once you have found it, switch it to the OFF position and leave it there for the entire job.

Use a non-contact voltage tester on the heater to confirm that power is off. Touch the tester to the heater body and to the wires inside the terminal block — if the tester does not light up or beep, the power is off and it is safe to work. If the tester lights up or beeps, the power is still on; go back to the breaker panel and try a different breaker.

Once you have confirmed the power is off, remove the cover plate or trim ring from the front of the heater by unscrewing the fasteners or prying it gently with a flat screwdriver. Take a photo of the wire connections inside the terminal block before you disconnect anything — this will help you reconnect the new heater correctly. Loosen the terminal screws and pull the wires out, then unbolt the heater from the wall brackets and slide it out.

Preparing the wall and brackets for the new heater

If your new heater is the same length as the old one, you can reuse the existing brackets. Wipe them clean with a dry cloth and check that the bolts move freely. If the new heater is longer or shorter, you will need to remove the old brackets and install new ones; most heaters come with brackets in the box, or you can order them separately from the manufacturer.

Before you install the new brackets, check the wall for studs using a stud finder. Baseboard heaters are heavy and need to be bolted into studs or into the wall with heavy-duty anchors. If the old brackets were bolted into studs, use the same holes. If they were not, drill new holes into studs and use lag bolts or wood screws; if you cannot hit a stud, use toggle bolts or heavy-duty plastic anchors rated for the weight of the heater.

Slide the new heater into the brackets and bolt it loosely — do not tighten the bolts all the way yet, because you may need to adjust the heater to align it with the electrical connection.

Connecting the wires to the new heater

Look at the terminal block on the new heater. It will have two or three terminals, usually labeled L1, L2, and sometimes G (for ground). The wires from the wall will be black, red, and possibly bare copper or green. The black and red wires carry power; the bare copper or green wire is the ground.

If the old heater had the same terminal layout, you can reconnect the wires to the same terminals on the new heater. If the layout is different, check the instruction sheet that came with the new heater — it will show you which wire goes to which terminal. Loosen the terminal screws, insert the wire about half an inch into the terminal, and tighten the screw firmly. Tug on the wire to make sure it does not pull out.

If the new heater is longer than the old one and the wires do not reach the terminal block, you will need to extend them. Turn off the breaker, cut the wires about six inches from the wall, strip about half an inch of insulation from each wire, and use wire connectors (also called wire nuts) to join the old wires to new wires that run to the heater. Twist the wires together clockwise, screw the wire connector on tightly, and wrap the joint with electrical tape. If you are not confident doing this, call an electrician.

Securing the heater and testing it

Once the wires are connected, tighten the bolts on the brackets so the heater is firmly attached to the wall. Make sure the heater is level by placing a level on top of it; if it is tilted, loosen the bolts and adjust the brackets until it is level, then tighten again.

Reinstall the cover plate or trim ring by screwing it back on or snapping it into place. Go back to the breaker panel and switch the breaker to the ON position. Wait a few minutes and feel the heater — it should be warm to the touch. If it is hot, that is normal; if it is cold, turn the breaker back off and check your wire connections.

If the heater is still cold after you have checked the connections, the problem may be a bad thermostat or a faulty heater element. Most baseboard heaters have a built-in thermostat that you can adjust with a dial or slider on the front; make sure it is turned up to a comfortable temperature. If the heater still does not warm up, turn off the breaker and call an electrician or the heater manufacturer.

Choosing a replacement heater that fits your space

Baseboard heaters come in standard lengths: 2 feet, 3 feet, 4 feet, 5 feet, 6 feet, and 8 feet. If your old heater is a standard length, ordering a replacement is straightforward — just match the length, wattage, and voltage. If your old heater is a non-standard length or if you want to upgrade to a higher wattage, you may need to order a custom heater or use two shorter heaters instead of one long one.

The wattage you need depends on the size of the room and how well it is insulated. A rough rule of thumb is 10 watts per square foot for a well-insulated room and 15 watts per square foot for a poorly insulated room. If your old heater was keeping the room warm, you can match its wattage; if the room was always cold, you may want to upgrade to a higher wattage or add a second heater.

Check the voltage of your old heater on the nameplate. Most homes have 240-volt service, but some older homes have 120-volt service. If you are not sure, look at your breaker — a 240-volt breaker is usually a double breaker (two switches side by side), while a 120-volt breaker is a single switch. Order a heater that matches your voltage; a 240-volt heater will not work on a 120-volt circuit and vice versa.

When to call an electrician instead

If the wires in the wall are damaged, corroded, or too short to reach the new heater, you should hire an electrician to extend or replace them. If the breaker is tripped or the heater does not turn on after you have checked the connections, there may be a problem with the circuit or the breaker itself, and an electrician can diagnose it. If you are not comfortable working with electrical wiring or if you are unsure about any step, it is better to hire a professional than to risk a fire or electrical shock.

An electrician can also help you if you want to upgrade to a higher wattage heater or if you want to add a second heater to a room. They can check whether your breaker and wiring can handle the extra load and install the new heater safely. The cost is usually $200 to $400 for a single heater replacement, depending on your location and the complexity of the job.

Frequently Asked Questions

Can I replace a 240-volt baseboard heater with a 120-volt one?

No. The voltage must match the circuit in your wall. A 120-volt heater plugged into a 240-volt circuit will burn out when ready, and a 240-volt heater on a 120-volt circuit will not work. Check the nameplate on your old heater and the breaker in your panel to confirm the voltage before you order a replacement.

Do I need a permit to replace a baseboard heater?

Most jurisdictions do not require a permit for replacing a heater with one of the same size and wattage, but some do. Call your local building department or check their website to find out what the rules are in your area. If you are upgrading to a higher wattage or adding a new circuit, you will likely need a permit and an inspection.

What if the new heater is shorter than the old one and leaves a gap?

You can cover the gap with a blank cover plate that matches the heater, or you can install a second shorter heater in the gap. Blank plates are available from the heater manufacturer or from hardware stores. If you install a second heater, make sure it is on a separate circuit or that your breaker can handle the extra load.

How long does a baseboard heater last?

Most baseboard heaters last 15 to 20 years before the heating element fails or the thermostat stops working. If your heater is more than 20 years old and stops working, replacement is usually cheaper than repair. Newer heaters are also more efficient and may have better thermostats that save energy.

Can I install a baseboard heater myself if I have never done electrical work before?

If you are comfortable following instructions and using basic tools, you can replace a heater if the new one is the same size as the old one and the wires reach the terminal block. If you need to extend wires, reroute them, or install new brackets, hire an electrician. The risk of a fire or shock is not worth saving a few hundred dollars.