Electric fireplace inserts

An electric fireplace insert is a self-contained firebox that drops into an opening you already have. That opening is usually one of two things: a masonry firebox left behind when a wood or gas fireplace was decommissioned, or a stud cavity framed specifically to receive one. The insert brings its own housing, its own glass or mesh front, and its own heater. You plug it in.

That is the whole idea, and it is worth stating plainly because the word "insert" gets used for at least three different products in this category. A log set is a bare tray of resin logs with a heater behind it — no enclosure, no glass, so the old firebox stays visible around it. A full insert is a boxed unit with a front, sized to fill the opening. A linear recessed unit is a wide, frameless band of flame designed for a cavity you frame yourself, and it belongs in the wall-mount section rather than here. Buying the wrong one of the three is the single most common mistake in this category, and it is entirely avoidable with a tape measure.

Every insert is sold by nominal width — 20, 26, 33, 36, 50 inches — and that number is the unit, not the hole. Masonry openings taper: they are frequently narrower at the back than at the front, and the back is what constrains you. Measure width at the front, width at the back, height, and depth, and write all four down. Then subtract nothing and add nothing, because the trim kit is what covers the difference, and trim kits are usually sold separately.

• Front width — what you see. This decides whether the finished result looks deliberate.
• Rear width — the real constraint. An insert that clears the front and fouls the back does not go in.
• Height — usually generous in masonry, tight in a framed cavity.
• Depth — a log set needs almost none; a full insert typically wants 8 inches or more.
• Power — where is the nearest receptacle, and is it on a circuit already carrying something else? See watts, amps and your circuit.

Heat output. Every plug-in electric fireplace sold in the United States runs on a 120 V circuit, and 1,500 W is the practical ceiling before you trip a standard breaker. That is about 5,118 BTU per hour, on every unit, at every price. A $200 log set and a $1,600 recessed linear unit produce the same heat, because physics and the National Electrical Code say they must.

The purchase price is the number everyone quotes. The one that matters over a winter is the running cost, and it is computable exactly: watts divided by 1,000, times your electricity rate. At the June 2026 US residential average of 18.34 cents per kWh, a 1,500 W insert costs 27.5 cents an hour on full heat — about $99 across a 90-day winter at four hours a night.

That figure is roughly 53% higher than the numbers still circulating in this category, which were computed at around 12 cents per kWh and never updated. We think being right about this is more useful than being cheerful about it. The full working, including the flame-only column that changes the calculation entirely, is on what these cost to run.

If you have a masonry firebox and want the least disruptive option, start with inserts for an existing fireplace. If you already know your opening, go straight to 36-inch or 50-inch. If you are still deciding whether the whole idea is worth it, are inserts worth it gives the honest conditional answer, and installation cost covers what you will spend beyond the box.