How to Install an Electric Fireplace Insert Safely in an Existing Fireplace
Joye
Updated September 29, 2026 11 min read
Bottom line
Installing an electric fireplace insert in an existing fireplace is a straightforward DIY job that usually takes 2 to 4 hours. It involves cleaning the firebox, sealing the chimney flue, ensuring proper electrical connections, sliding in the insert, and finishing with trim kits.
Many homeowners believe electric fireplace inserts need complex wiring or professional installation. The truth is, most models plug into a standard 120V outlet and require no venting or gas connections. You only need a few tools, some basic electrical safety knowledge, and a careful approach to chimney sealing and fit.
This guide breaks down the process into clear steps, covering preparation, installation, common pitfalls, and when to call a pro. It also explains how to match your insert size and style to your existing fireplace for a clean, efficient upgrade.
What to remember
Measure your fireplace opening carefully before buying an insert to ensure a proper fit.
Most electric fireplace inserts plug into a standard 120V outlet; a dedicated circuit is ideal but not always required.
Seal the chimney flue and damper completely to prevent drafts and heat loss.
Use the included leveling brackets or shims to secure the insert safely inside the firebox.
Check local codes and consider a licensed electrician if you’re unfamiliar with electrical work or if the installation requires new wiring.
How to Install an Electric Fireplace Insert Safely in an Existing Fireplace
An electric fireplace insert fits an existing fireplace when the opening, firebox depth, and electrical supply match the insert’s installation instructions. Prepare the opening, make the chimney safe from drafts, test the heater, then slide it in and finish the edges with a trim kit or surround.
Ensure the insert fits properly in the fireplace.
That approach also works in an old gas fireplace box after the gas supply is disconnected and capped by a qualified professional, provided the firebox is sound and the insert manufacturer allows that installation. Electric inserts produce no combustion gases, so they don’t need a chimney for venting.
1
Measure the opening
Measure the opening’s width, height, and depth in several places, then compare the smallest measurements with the insert’s required opening. Check the back of the firebox too; a wide mantel opening doesn’t help if the rear narrows. SimpliFire inserts, for example, come in 25-, 30-, and 35-inch sizes, so insert sizes aren’t universal.
2
Clean and inspect the firebox
Remove ash, soot, loose mortar, gas logs, and debris with a vacuum rated for fine particles. Inspect masonry or prefab panels for cracks, water damage, or loose parts. Check the chimney flue and damper for damage and confirm the damper can close fully. A gas fireplace needs its fuel supply handled before any electrical work begins.
3
Seal the flue and damper
Close and secure the damper, then seal gaps around the damper or flue opening with a suitable high-temperature sealant or approved closure method. The insert doesn’t need venting, but an open chimney can pull heated room air outdoors and bring cold drafts back through the firebox.
4
Confirm the electrical supply
Find a properly grounded 120-volt wall outlet that can reach the insert without pinching the cord. Many inserts use a standard outlet; a 15-amp circuit is required for models with that specification, and larger heaters may be better served by a dedicated circuit. Don’t use a power strip or extension cord to run the fireplace.
5
Test the insert first
Before sliding the unit into the firebox, inspect the cord and plug, remove shipping brackets if the manual says to, and run the flame and heater functions from the outlet. Confirm the thermostat, remote control, and manual buttons respond. Finding a damaged part before installation beats removing the trim later.
6
Set and secure the insert
Place the unit on the firebox floor, center it, and use the supplied leveling brackets or noncombustible shims to keep it stable. Follow the manual for anchoring; don’t drill through hidden wiring or damage a prefab firebox panel.
7
Fit the trim and check clearances
Install the trim kit or surround to hide the opening, shims, and cord without crushing the wiring. Leave every clearance required by the manual, including space above the mantel and around the heater outlet; electric fireplace clearance rules are easy to miss when an old opening is tight.
Useful for sizing and finishing
Westinghouse 50 Inch Electric Fireplace Heater
Product 1 suits a wall or recessed opening measuring 49 by 15 by 6 inches, and its interchangeable log and crystal ember beds can help finish a suitably sized opening; skip it if your firebox is smaller or can’t provide its required 11.8 inches of clearance above.
Keep the heater plugged directly into the wall outlet, maintain 3 feet of clearance from combustibles unless the manual gives a more specific arrangement, and don’t leave it running unattended or while you sleep unless the manufacturer specifically permits that use.
Tools and Parts You’ll Need
Choose an insert that fits the firebox opening and matches the electrical plan before you start framing or trimming.
Best for Wide Openings
Westinghouse 50-Inch Electric Fireplace
The recessed-install dimensions give you a clear target for measuring the firebox before you buy. Its 750W/1500W heat settings and built-in thermostat also let you use it for flame effects or supplemental heat, provided the recommended 120V 15A circuit has no other appliances on it.
The 31-inch format is easier to work into a modest firebox or a newly framed opening than a wide insert. Twelve flame and LED flame-bed color modes handle the visual side, while the 750W/1500W settings and overheat protection cover occasional supplemental heat.
Gather the measuring, cleaning, sealing, and fastening parts before installing an electric fireplace in a wall or existing firebox; the right kit prevents a loose insert and a visible cable afterward.
Gather essential tools and materials before starting the installation.
Tape measure and level for the fireplace opening, firebox floor, and trim.
Vacuum and cleaning supplies for ash, soot, dust, and loose debris.
High-temperature silicone sealant approved for the damper or flue area.
Screwdrivers and a drill, used only where the manufacturer’s instructions allow fastening.
Leveling brackets or noncombustible shims, usually included with the insert.
A grounded 120-volt wall outlet. An extension cord may power a work light temporarily, but never run the fireplace through one.
Paintable wire channels or another cable-management method that keeps the cord protected and visible for inspection.
Model-specific brackets
For an SE316-50P bracket installation, use the bracket locations and fasteners supplied for that model; don’t substitute holes or hardware from another insert. The same rule applies when learning how to install an electric heater: the manual controls the mounting method, clearances, and electrical connection.
Keep the trim or surround nearby before you start. A surround can hide a small gap, but it can’t correct an insert that doesn’t fit the opening.
Electrical Safety Checks and Wiring Tips
Yes, you can usually plug an electric fireplace insert directly into a grounded wall outlet if the model’s instructions allow it. Most inserts use 120 volts on a 15-amp circuit, often with a standard NEMA-5-15P plug. An insert can go into an old wood fireplace because it produces no combustion gases and needs no chimney venting; the outlet and firebox still need inspection.
1,500 W
Approximate upper limit for a standard 15-amp, 120-volt circ
A 1,500-watt heater draws about 12.5 amps, leaving little capacity for other appliances on that circuit.
A dedicated circuit is the better choice for an insert over 1,500 watts or for any unit sharing its circuit with lights, a television, or another heater. Check the breaker rating, reset it once, and inspect the outlet for looseness, scorch marks, cracked plastic, or warmth before installation.
No Extension Cord
Never make an extension cord or power strip the permanent connection. Overloaded cords and circuits can overheat and cause an electrical fault.
If the firebox has no suitable outlet, have a licensed electrician install one and handle any new wiring. Don’t bury a cord behind the insert or force a plug into an outlet that doesn’t match the manufacturer’s instructions.
Common Mistakes That Cause Damage or Drafts
Prepare the fireplace by cleaning the firebox, checking the opening, sealing the chimney flue and damper, and confirming the insert’s clearances. For an existing gas fireplace box, remove the gas appliance and have the gas connection safely disconnected before fitting an electric insert; the electric unit itself needs no gas line or vent.
Leaving the damper or flue open creates a draft that pulls heated room air up the chimney. Soot, ash, broken masonry, and old hardware can also keep the insert from sitting squarely, so clean the firebox before sliding it in.
Follow the insert’s clearance rules around wood, drywall, trim, and other combustibles. Secure the unit with its leveling brackets or suitable shims, then fit the surround or trim kit; an unsecured insert can shift, strain the cord, and damage the finish.
Check Before Powering Up
Don’t use an extension cord, overload the circuit, or trap the power cord behind a sharp edge. Those shortcuts turn a tidy fireplace update into a very poor electrical experiment.
When to Get Permits or Call a Licensed Professional
An electric fireplace usually costs less to install than a gas fireplace because it needs no gas line, venting, or combustion inspection; gas work and venting add labor and permit requirements. See the typical gas fireplace installation costs before comparing quotes.
You can’t install an electric fireplace literally anywhere: the opening, firebox depth, clearances, grounded 120V supply, and manufacturer instructions all have to match. Most inserts plug into a standard outlet, but new wiring or an outlet installation may require a permit.
Have a licensed electrician wire a dedicated 15-amp circuit or upgrade the panel. If you’re unsure about electrical code, chimney condition, or the damper, call a qualified professional. An electric insert needs no gas line or venting, which keeps the job simpler.
An electric water tank with no existing power connector is a separate electrical project; don’t improvise an adapter. A licensed electrician should install the correctly sized circuit, and local permits may apply.
Final Checklist Before Buying, Installing, or Calling a Technician
An electric insert belongs in a wood buffet console only when the model permits that installation and its clearances protect the wood; don’t put a standard electric heater inside a small woodburning stove unless the manufacturer specifically approves that use.
Confirm Before You Buy
Measure the fireplace opening width, height, and depth; compare all three with the insert’s specifications.
Confirm a grounded 120V outlet is within reach, or plan permitted wiring with an electrician.
Inspect the chimney flue and damper, then seal the flue as the instructions require.
Gather a tape measure, level, fasteners, shims, and approved sealant.
Read the manufacturer instructions, heat clearances, and electrical requirements.
Choose a trim kit or surround that covers the opening without blocking controls or airflow.
Check local code and permit rules before new wiring, outlet work, or structural changes.
Questions People Ask
Can I plug an electric fireplace insert into a regular wall outlet?
Usually, yes, if the insert is designed for a grounded 120-volt outlet and its plug reaches the receptacle without an extension cord or power strip. Check the label and manual for the required circuit; a typical plug-in model uses a NEMA-5-15P plug, while a hardwired model needs an electrician.
Do I need a dedicated circuit for my electric fireplace insert?
A dedicated circuit isn’t required for many plug-in inserts, but it’s a sensible choice for a larger unit or a circuit already serving other heaters. A 15-amp, 120-volt circuit is common; don’t share it with another high-wattage heater, and stop if the breaker trips or the receptacle feels warm.
How do I seal the chimney flue and damper properly?
Close the damper fully, then use a chimney plug or other listed sealing method approved for your fireplace and insert. An old wood-burning chimney should be inspected and cleaned before sealing, and you shouldn’t stuff loose insulation, cardboard or combustible material into the flue.
Can I install an electric fireplace insert in a gas or wood-burning fireplace?
Yes, after the original fuel appliance is safely taken out of service and the firebox is sound, clean and dry. Have a licensed professional disconnect and cap a gas line, and keep the electric insert’s required clearances; the new unit produces no combustion gases, so it doesn’t need an open chimney.
What tools are necessary for installing an electric fireplace insert?
For a plug-in installation, you’ll generally need a tape measure, level, flashlight, vacuum, screwdriver and the supplied fastening hardware or shims. A soft brush helps remove soot and dust without scratching the firebox, while a stud finder is useful if the trim or surround attaches to the wall.
Is professional installation recommended for electric fireplace inserts?
DIY installation is reasonable when the insert is plug-and-play, the outlet is grounded, and no wiring changes are needed. Call a licensed electrician for a new outlet, a dedicated circuit or hardwiring, and use a qualified chimney or gas professional if the old fireplace has venting or gas connections that need inspection or alteration.
Are there size standards for electric fireplace inserts to fit existing fireplaces?
There isn’t one universal insert size, so match the manufacturer’s minimum opening width, height, depth and clearance requirements to your fireplace. Some product lines come in 25-, 30- and 35-inch sizes, but masonry openings vary; measure the front, rear and depth because an opening that looks square may not be.
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Written byJoye
HeaterGuides covers home heating, water heating and HVAC: how the equipment works, what it costs to run, and how to use it safely.
