Electric Fireplace Insert in an Existing Fireplace

Last reviewed: October 16, 2026

An electric fireplace insert is a self-contained flame and heater unit that sits inside an existing fireplace opening, and whether it fits depends on three measurements, one power decision, and the condition of the flue behind it. This guide walks through each step in the order a remodel usually runs, so you know what to check before you order and what to hand to a pro.

Quick answer: what has to be true for an insert to work

An electric insert works in an existing fireplace when the unit fits the narrowest part of the firebox, power can reach it safely, and the flue has been checked by someone qualified.

Check	What to confirm	Where to look
Fit	Width, height, and depth at the narrowest point of the opening	Tape measure, then the model's manual
Power	A compliant 120V supply that reaches the firebox, or a hardwire plan	Manual, local code, and an electrician
Flue and damper	Condition of the chimney and a plan for the damper	A chimney professional
Finish	How the gap between the unit and the masonry gets covered	Trim kit or surround for the model

Step 1: Measure the firebox before you shop

Measuring a masonry firebox means taking width, height, and depth at more than one point, because most openings taper toward the back and a few have a lintel that lowers the height near the front.

Measurement	Where to take it	Why it matters
Width	Front opening and rear wall	The smaller number controls fit
Height	Left side and right side, at the front and at the rear	A lintel or sloped roof can lower it
Depth	Front face to back wall, at the top and at the bottom	The shallowest reading controls fit
Hearth	How far the hearth projects and what it is made of	Affects trim and finish choices

Take those numbers to the model's cut sheet and compare them with the framing or installation dimensions, not the advertised width. Cabinet size, visible opening, and required opening are three different measurements, and our guide on how to measure your space for an electric fireplace covers the general method.

Step 2: Choose an insert that matches the opening

The Very Good Fireplaces electric fireplace inserts collection includes models from about 22 inches to over 70 inches wide, so the opening you measured narrows the list quickly.

If you are matching a traditional firebox, the Modern Flames Orion Traditional Built-In Series is one of the first places I would look. It comes in 26, 30, 36, 42, and 54 inch widths, lists up to 9,000 BTU on supported models, and is described by the manufacturer as suitable for many existing wood-burning fireplace openings. The Modern Flames Redstone Built-In Series covers the same five widths with a lower heat rating of up to 5,000 BTU and a trim kit included.

Insert	Widths	Power and connection	Trim
Modern Flames Orion Traditional	26, 30, 36, 42, 54 in.	120V; 240V option on 36, 42, and 54 in. models	Check the model's manual
Modern Flames Redstone	26, 30, 36, 42, 54 in.	120V; plug-in cord for insert installs, hardwired for new built-ins	Trim kit included
Touchstone Fireplug Pro	24, 29, 33, 38 in.	120V, up to 1,500W; plug-in or hardwire	Optional 2 in. and 4 in. kits sold separately
Amantii Fire & Ice Classic Edition	26, 30, 33 in.	120V, 1,500W, 12.5A	Fixed trim included

For a smaller or lower-budget conversion, the Touchstone Fireplug Pro lists an overall depth of 7 7/8 inches across its four sizes, which can help in a shallow firebox. Treat every number here as a starting point and confirm it against the manual for the exact size, since the unit's overall dimensions are not the same as its required opening.

Step 3: Decide what to do about the damper and flue

The damper is part of the chimney, not part of the insert, and an electric unit does not need a draft because nothing burns inside it.

That does not mean the flue can be ignored. If the chimney has not been looked at in years, or you plan to reuse the wood fireplace someday, have a chimney professional inspect it before you commit. NFPA 211 is the standard that defines chimney inspection levels, and a deeper inspection is typically used when the appliance or fuel type changes. Ask the professional whether one applies to your conversion. Do not cut, remove, or modify the damper or masonry to make a unit fit unless the manual and a qualified pro say it is acceptable.

Step 4: Bring power to the firebox

Power for an insert comes from either a 120V outlet placed where the manual allows or a hardwired connection made by a qualified electrician.

An older wood-burning firebox rarely has an outlet inside it, so plan for one early. The Redstone manual, for example, describes the supplied plug-in cord for insert installations, and the Fireplug Pro lists a 15-amp circuit with a 1,500W maximum. Neither number is a rule for every model: use the nameplate and manual for the unit you buy, and do not rely on an extension cord or a shared power strip. Our guides on electrical requirements and plug-in versus hardwired installation explain how those two questions differ, and the installation cost guide helps you put the electrician in the budget.

Step 5: Close the gap with trim and a surround

A trim kit is a metal or finished frame that covers the space between the insert and the masonry opening, which is the part that makes a conversion look finished.

Some models include trim and some sell it separately, so decide this before ordering. If the opening is much larger than the unit, you may need a deeper trim, a custom surround, or new framing, and the guide to building a frame for an electric fireplace insert covers that work in detail.

Insert, built-in, or wall-mounted: which path fits

An insert is the right path when you have a usable masonry or factory-built opening, and a built-in or wall-mounted unit makes more sense when you do not.

Your situation	Best path	Why
Usable wood-burning firebox that fits a standard insert	Insert	The opening is already there
Opening too large or oddly shaped	Insert with a custom surround, or a built-in	New framing can correct the proportions
No fireplace at all	Built-in or wall-mounted	No opening to reuse
Want to keep wood burning available	Compare first	See our electric versus wood-burning inserts guide

Common mistakes

The most common mistake is buying on advertised width instead of measuring the narrowest point of the firebox. The second is leaving power until after the unit arrives, and the third is skipping the chimney conversation because the new appliance does not need a flue. A quick measurement and two phone calls, one to an electrician and one to a chimney professional, usually settle all three.

Frequently asked questions

Can I put an electric fireplace insert in a wood-burning fireplace?

Often yes, when the firebox is deep, wide, and tall enough for the model you choose and power can reach the opening. Measure the narrowest width, height, and depth first, then compare them with the model's manual, because the opening decides which inserts are candidates.

Do I need to remove the damper to install an electric insert?

Do not assume so. Whether the damper stays open, stays closed, or needs any change depends on the insert's manual and the condition of the flue, so ask a chimney professional before cutting or removing any masonry or damper parts.

Does an electric fireplace insert need to be hardwired?

It depends on the model and the installation method. The Modern Flames Redstone manual, for example, uses the supplied plug-in cord for insert installations and hardwiring for new built-ins, while the Touchstone Fireplug Pro can plug into a standard 120V outlet or be hardwired. Check the manual for the exact unit.

Can the insert go in a tapered or shallow firebox?

Only if the narrowest measurement still clears the model's required dimensions. A tapered firebox is controlled by its rear width and its shallowest depth, so use the smallest number you find rather than the opening you see at the front.

Will an electric insert heat the whole room?

It adds supplemental heat to the room it sits in. The Modern Flames Orion Traditional lists up to 9,000 BTU on supported models and the Redstone lists up to 5,000 BTU, so treat either as a way to warm one space and not as a replacement for central heat.

Do I still need to maintain the chimney after converting to electric?

The insert itself produces no combustion, but the chimney is still part of the house. Ask a chimney professional how to handle the damper and flue so water, drafts, and animals stay out, especially if you ever plan to return to wood.

Final thought

Measure first, settle the power plan second, and have the flue looked at before the unit is ordered. If you would like a second set of eyes on your opening, send us the measurements and we will point you toward inserts worth considering.