Quick Answer: Size an electric fireplace’s width to your wall and TV — a few inches narrower than the screen above it, roughly 50–60 inches for a 65-inch TV — and size its heat separately, since almost every plug-in unit is rated by manufacturers at 1,500W / ~5,000 BTU / ~400 sq ft regardless of width. Going recessed needs about 5–7 inches of depth, which fits a standard 2x6 stud wall (~5.5 inches) but not a 2x4 (~3.5 inches). Get the width, mounting height, and recess depth right and the unit reads as built-in instead of bolted-on.
Getting the size right is the difference between an electric fireplace that looks built-in and one that looks bolted-on. And there are really two sizes to think about: the physical size (how it fits your wall and TV) and the heat size (how much room it can warm). They’re not the same thing. This guide covers both, with real numbers.
Physical size vs. heat size — don’t confuse them
The most common sizing mistake is assuming a wider fireplace heats a bigger room. It doesn’t. Almost every plug-in electric fireplace is 1500W / ~5,000 BTU / ~400 sq ft, whether it’s 36 inches or 72 inches wide, because they all max out a standard 120V outlet. That 1,500W figure isn’t arbitrary — a standard 15-amp residential circuit is rated for 1,800 watts, and the National Electrical Code’s 80%-continuous-load rule caps safe sustained draw at roughly 1,440W, so manufacturers standardize on 1,500W to stay just inside that headroom on a shared circuit. Width is about looks and proportion; heat is capped by the outlet. Size the width to your wall and TV, and size the heat by adding units if a single one can’t cover the room — or by moving to a genuinely higher-voltage model. Our best SimpliFire electric fireplace guide covers the Scion, one of the few units that breaks past the standard 1,500W/400 sq ft ceiling with an optional dedicated 240V circuit.
Sizing the width to your wall and TV
| TV size | TV width (approx.) | Suggested fireplace width |
|---|---|---|
| 50" | ~44" | 36"–50" |
| 55" | ~48" | 42"–50" |
| 65" | ~57" | 50"–60" |
| 75" | ~66" | 60"–72" |
Aim for a fireplace slightly narrower than the TV above it so the screen stays the hero and the flame reads as a base of warmth beneath it. If there’s no TV, size to the wall instead — a linear unit centered on a wall generally looks best at roughly one-third to one-half the wall’s width. Measure your actual wall and any media console before ordering. Pairing with a smaller 40-50” TV on a compact wall? See our best 40-inch electric fireplace picks. Pairing with a 55-65” TV? See our best 50-inch electric fireplace picks. Pairing with a standard 65-75” TV on a typical media wall? See our best 60-inch electric fireplace picks. Pairing with a genuinely large screen (75” or up) or a great-room-scale wall? See our best 72-inch electric fireplace picks.
Mounting height
For a wall-mount or recessed unit, center the flame around 40–42 inches off the floor for comfortable standing and seated viewing. If a TV goes above it, put the top of the fireplace just below the TV with clearance for rising heat — Dimplex, one of the brands featured across this site’s reviews, specifies 8–10 inches minimum between the top of the firebox and the bottom of the TV on its front-heat-vent models, and always respect the model’s own stated minimum clearance to combustibles, since fan-forced units vent warm air upward and too little gap can overheat the screen above.
Recess depth (if you’re going flush)
Going recessed for that built-in look? Depth is where projects go wrong:
- Most recessed linear units need ~5–7 inches of depth.
- A 2x6 stud wall (~5.5” actual) usually works.
- A 2x4 wall (~3.5” actual) is typically too shallow — you’d need to fur the wall out or build a bump-out.
- Always confirm the specific model’s rough-opening width, height, and depth before framing.
For real manufacturer depth measurements by model — from a 3.85” ultra-thin recessed unit to an 8.9”-deep firebox insert — see our electric fireplace dimensions breakdown.
If cutting into a wall isn’t an option, a surface-mount install (hangs like a TV) needs no depth at all — see our best wall mount electric fireplace picks, most of which do both.
Working with an RV or trailer wall instead of standard home framing? Those cavities are usually too thin for the 5–7” units above — see our best electric fireplace for RV guide for units built at 3–5” deep specifically for camper cutouts.
Sizing for an existing firebox (inserts)
Replacing an old wood or gas firebox instead? Then you’re sizing an insert, and the rules flip: measure the existing opening’s width, height, and depth — front and back, since masonry fireboxes often taper narrower toward the rear — and buy an insert that fits the smallest measurement with a little clearance. Inserts are sold by nominal width (23”, 28”, 33”, 36”); match that to your opening, not your room. Our best electric fireplace insert guide breaks down the options, and if you need a frame around a bare insert rather than an all-in-one package, our best electric fireplace surround guide covers frame-only kits sized to standard openings. Once you’ve picked the right size, our how to install an electric fireplace insert walkthrough covers the actual install process, from capping the chimney to leveling the unit.
Heating a large or open room
Sizing rules here assume an indoor installation — a covered porch or patio needs a weatherproof outdoor-rated model instead, since standard indoor units aren’t sealed against moisture. Installing in a basement instead? Concrete and block walls change the mounting math entirely — see our best electric fireplace for basement guide for freestanding options that skip the recess cutout.
Because a single plug-in unit is capped at ~400 sq ft, a big open-plan space needs a different plan:
- Add a second unit on another wall/outlet, or
- Use a freestanding infrared model, which heats a larger area faster and holds humidity better — see how infrared heat actually works for the technology behind that claim, or
- Treat the fireplace as ambiance and rely on central heat for the whole room.
Whichever route you pick, running the fireplace instead of turning down central heat elsewhere — not in addition to it — is what actually saves money on the bill; see our electric fireplace energy efficiency guide for the real numbers behind zone heating.
Don’t buy a wider fireplace expecting more heat — you’ll get more flame, not more warmth.
Quick sizing checklist
- Measure the wall width and any TV/console below.
- Pick a fireplace a few inches narrower than the TV above it.
- Plan the flame center around 40–42 inches high.
- Going recessed? Confirm 5–7 inches of depth (2x6 wall, not 2x4).
- Sizing an insert? Measure the opening front and back, buy to the smallest.
- Remember heat is ~400 sq ft regardless of width — add units for big rooms.
The bottom line
Size the width to your wall and TV for looks, and size the heat by room — remembering that every plug-in unit tops out around 400 sq ft no matter how wide it is. Nail the recess depth (2x6, not 2x4) if you’re going flush, and measure an existing firebox front-and-back before buying an insert. Get those numbers right and the fireplace will look like it was always meant to be there. Ready to shop? Start with our best electric fireplace rankings.