How to Choose an Electric Fireplace Insert | Fit, Heat & Power

The difference between a great electric fireplace insert and a frustrating one usually comes down to numbers on a tape measure, not brand names. Before you shop, you need to know your opening’s dimensions, your electrical setup, and how much heat you actually want. Get those three things right, and the rest is about style.

Measure Your Existing Fireplace Opening First

An insert must fit your current fireplace opening, so this is the first and most important step. You need to measure four dimensions: the front width at its narrowest point, the back width, the depth, and the height of the opening.

Manufacturers publish these minimums for each size. SimpliFire’s current insert lineup, for example, comes in 25-inch, 30-inch, and 35-inch widths, and each size has its own minimum opening requirements that you should check against your measurements. Consumer Reports notes that tested inserts have ranged from about 23 inches to 36 inches wide, so measure carefully and give yourself a little wiggle room—an insert that’s even half an inch too wide won’t go in without modification.

Decide On Heat Output (BTUs) And Voltage

Some provide just enough warmth to take the chill off a room; others are powerful enough to heat a larger space. This matters because it affects the type of outlet you need.

Heat output is measured in BTUs. Check what your home supports before you commit.

This is where many buyers get tripped up. The bigger, hotter units usually require a dedicated 240V circuit, which is a job for a licensed electrician if you don’t already have one. Always match the insert’s electrical needs to your home’s capacity.

Match The Mounting Style To Your Space

Not all electric fires are interchangeable, so it’s crucial to know the difference. Consumer guidance from Lowe’s identifies electric fireplaces as either all-in-one units or fireplace inserts that fit into an existing fireplace and chimney. The insert category is what you want if your goal is to convert an old wood-burning fireplace.

Within inserts, there’s another distinction. Some models are designed for built-in or framed openings (like a new-construction fireplace), while others are marketed specifically as wall-mount or recessed units. You can install most inserts into an existing mantle or fireplace, or as part of new construction, but the mounting format must match where you plan to put it. A model meant for a framed opening isn’t a simple drop-in for an old masonry fireplace.

Viewing area is worth considering too. SimpliFire lists viewing areas of 22 x 12 inches, 27 x 16-1/4 inches, and 32-1/8 x 19 inches for its 25-, 30-, and 35-inch inserts. A larger viewing area makes the fire feel more like the real thing, which is often the whole point.

Pricing is model-specific and changes, but plan for a significant investment. If you’re looking for a tested roundup of specific models, our best electric fireplace insert with heater guide covers top picks across price ranges.

Installation And Safety Basics

Installation can be a plug-in job or a hardwired one. A plug-in insert is the simplest choice if you want to avoid hiring an electrician. These simply plug into a standard 120V grounded outlet. Hardwired models are wired directly into a junction box—a cleaner look, but a job that may require professional help. Some models offer both options, while others are hardwire-only, so read the specs carefully.

Manufacturer instructions also advise choosing a location away from moisture, drapes, furniture, and high-traffic areas. You should also follow all national and local electrical codes. Unlike wood-burning fires, electric inserts produce no real flames or fumes, but the electrical load still demands respect. Don’t assume you can swap a 120V plug-in for a 240V hardwire model without checking your panel first.

When you’re ready to start comparing specific models, Consumer Reports and Lowe’s both offer solid buying guidance. Lowe’s electric fireplace buying guide breaks down the main types and what to look for in each.

The bottom line: measure your space exactly, know how much heat you need, and confirm your electrical capacity before you fall in love with a specific style. That one hour of measuring and checking will save you from a costly return.