The best electric fireplace inserts for existing fireplaces are the ones that leave enough clearance around the firebox, deliver roughly 4,400–5,100 BTU of supplemental heat, and include flame effects that still look convincing at your normal viewing distance.
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Top 3 picks at a glance
Quick comparison: which insert fits your situation?
| Fireplace situation | Best-fit choice | Typical size class | Heating output | Why it fits |
|---|---|---|---|---|
| Small masonry opening | Compact 23–24-inch electric insert | About 24–28 inches wide, 20–24 inches high | 1,350–1,500 W; up to about 5,100 BTU | Leaves room for trim or a safe air gap without rebuilding the opening |
| Standard 30-inch firebox | Dimplex Revillusion 25 or Napoleon NEFI24H-class insert | About 27–31 inches wide, 23–27 inches high | Usually 1,500 W; about 5,100 BTU | Strongest selection of realistic logs, glass fronts, and surround options |
| Wide fireplace opening | Dimplex Revillusion 30 or larger Napoleon NEFI model | About 31–38 inches wide, 26–32 inches high | Usually 1,500 W; heat remains similar to smaller models | Fills a broad opening without making the flame display look undersized |
| Decorative fireplace with little need for heat | Low-heat or flame-only insert | Choose by opening dimensions | Heat can be disabled | Allows year-round flame effects without warming the room |
Product dimensions differ between trim packages, so treat these as selection ranges rather than installation measurements. Measure the actual unit, including its rear cabinet and front trim, before ordering.
Best electric fireplace inserts for existing fireplaces
Best all-around flame realism: Dimplex Revillusion series
The Dimplex Revillusion series is a strong choice when the appearance of the fire matters more than maximum heating area. Its partially concealed display design creates the impression of flames rising through a log set instead of simply playing behind a flat black panel. The series is available in multiple width classes, including models commonly sold as the Revillusion 25, 30, and 36.
Most versions provide a 1,500-watt heater, adjustable flame brightness, ember-bed lighting, and thermostat control. That output is suitable for supplemental heating, but it should not be treated as a whole-home heating system. A larger 36-inch model generally gives you a wider visual display rather than more heat; the heater remains close to the same electrical limit.
Choose the Revillusion 25-class unit for an opening around 27–30 inches wide. Move to the 30-class model when the opening is approximately 31–35 inches wide, and consider the 36-class version for a broad opening where a smaller insert would leave conspicuous gaps.
Best for traditional fireplace styling: Napoleon NEFI series
Napoleon’s NEFI electric insert range is aimed at homeowners who want a conventional log-and-ember appearance, a glass-fronted installation, and a finished surround that looks at home in a masonry fireplace. The range includes several width categories, such as NEFI24H, NEFI27H, NEFI29H, NEFI32H, and NEFI36H.
The advantage is choice: you can match the insert more closely to the fireplace opening instead of using a small unit with a large decorative frame. Many models offer flame and ember brightness controls, multiple flame colors or display settings, remote operation, and supplemental heat around the 1,500-watt class.
Napoleon is particularly suitable when your existing fireplace has a rectangular opening and you want the surround to hide uneven masonry edges. Check whether the selected package includes the trim you need; the insert cabinet and the finished outer frame are not always the same dimensions.
Best when you want a modern, minimal display
For a contemporary room, look for a recessed electric firebox with a shallow cabinet, adjustable flame color, and a clean glass front rather than a prominent traditional surround. Models in this category are often sold as built-in fireboxes as well as inserts. They can work in an existing fireplace, but installation is less forgiving because the opening must be square and the finish around the unit needs to be neat.
Choose this style when the fireplace is being renovated with stone, tile, plaster, or a custom mantel. For a quick replacement inside an old opening, a traditional insert with an overlapping trim kit is usually easier.
How to measure an existing fireplace correctly
- Measure the opening width at the front, middle, and rear. Old masonry openings are often wider at the face than at the back. Use the smallest measurement when evaluating the cabinet.
- Measure height on both sides and in the center. A slightly uneven lintel can prevent an insert from sliding fully into place.
- Measure depth from the face to the rear obstruction. Include the space occupied by the power cord and avoid assuming that a shallow-looking front has a shallow cabinet.
- Check the hearth height and front trim. The insert may fit inside the cavity but still collide with a raised hearth or mantel trim.
- Allow space for ventilation and service access. Do not pack insulation, wood, or masonry debris tightly against heater outlets or intake openings.
A useful rule is to leave roughly 1–2 inches of visual or installation tolerance around the cabinet unless the manufacturer specifies a different requirement. The front trim may cover a larger gap, but it should not be used to force an oversized cabinet into a narrow cavity.
Heating output and the electrical calculation that matters
Most full-power electric fireplace inserts use 1,500 watts on a 120-volt supply. The current draw is:
1,500 W ÷ 120 V = 12.5 amps
That is close to the practical capacity of a 15-amp circuit once other loads are included. For example, if the same circuit also powers a 300-watt television and a 100-watt sound system, the combined demand becomes 1,900 watts, or about 15.8 amps. That can trip the breaker or create an unsuitable continuous load.
Before installation, identify what else shares the outlet or circuit. A dedicated circuit is preferable for a 1,500-watt heater, especially in an older home. Never use an extension cord or power strip unless the manufacturer explicitly permits it; most fireplace manuals prohibit them. If the receptacle is inside the old fireplace, have an electrician confirm that it is correctly grounded and positioned away from heat and moisture.
Flame effects: what changes the appearance most?
- Depth behind the logs: A deeper ember bed creates better separation between the logs and flame projection than a flat screen.
- Ember lighting: Adjustable ember brightness helps the display look convincing in daylight without becoming excessively bright at night.
- Flame color controls: Amber-only flames tend to look traditional, while blue or multi-color modes suit modern rooms but can appear less natural.
- Glass reflection: A glossy front can reflect lamps and windows. Positioning the insert away from direct light may improve the effect more than changing settings.
- Viewing height: Flame displays usually look best near eye level when seated. A very low insert can make the top of the display difficult to see.
If realism is your priority, select the largest insert that fits without crowding the opening, then use a moderate flame brightness and a low-to-medium ember setting. Maximum brightness can flatten the contrast between the flames, logs, and background.
Installation requirements beyond “plug it in”
An electric insert does not require a chimney, gas line, or combustion-air supply, but the existing fireplace should still be inspected. Remove ash, soot, loose mortar, and flammable debris. A permanently unused chimney may need to be capped or otherwise managed to prevent rain, drafts, and debris from reaching the insert area, subject to local building requirements.
Keep the heater outlet unobstructed. Do not install curtains, shelves, cushions, or combustible trim directly over the warm-air discharge. Mantel clearance is model-specific, so follow the selected unit’s manual rather than applying a generic distance.
For a masonry fireplace, a trim kit is usually the simplest finish. For a prefabricated metal fireplace, confirm that the insert is approved for that type of enclosure; the cavity may contain insulation, vent components, or clearances that differ from masonry construction.
Which one should you buy?
- Choose a Dimplex Revillusion 25-class insert for a medium opening and the most convincing log-and-flame presentation in a compact format.
- Choose a Dimplex Revillusion 30- or 36-class insert when the fireplace is wide and you want the display to fill it visually.
- Choose a Napoleon NEFI model when traditional styling, multiple width options, and a finished surround are more important than a minimalist appearance.
- Choose a modern recessed firebox for a remodel with a square opening, contemporary finish, and flame-only operation as a major feature.
The right purchase is determined first by the smallest opening measurement, then by the circuit’s available capacity, and only afterward by flame colors and styling. A correctly sized 1,500-watt insert with a good trim fit will usually look more integrated—and operate more reliably—than a larger, feature-rich model forced into an unsuitable fireplace.
Frequently asked questions
Can an electric fireplace insert heat an entire home?
No. These inserts are intended for supplemental heating rather than whole-home heating. Many full-power models use 1,500 watts and provide about 5,100 BTU, while some operate at 750 watts for lower heat. A larger insert generally creates a wider visual display, not substantially more heat, because the heater remains close to the same electrical limit.
Do I need to keep the chimney open when installing an electric insert?
No chimney is required for an electric insert because it does not use combustion. However, the existing fireplace should be inspected and cleaned of ash, soot, loose mortar, and flammable debris. A permanently unused chimney may need to be capped or otherwise managed to limit rain, drafts, and debris, subject to local building requirements.
Can I use an extension cord or power strip with an electric fireplace insert?
Usually no. Most fireplace manuals prohibit using an extension cord or power strip unless the manufacturer explicitly permits it. A 1,500-watt unit on a 120-volt supply draws 12.5 amps, so identify other devices sharing the circuit. A dedicated circuit is preferable, especially in an older home.
Will the front trim cover gaps around an insert?
It may cover a larger gap, but trim should not be used to force an oversized cabinet into a narrow cavity. Measure the actual opening and the insert’s cabinet, rear section, and front trim separately. Leave roughly 1–2 inches of tolerance unless the manufacturer specifies otherwise, and check for an uneven lintel or raised hearth.
Which flame settings usually look most natural?
Amber-only flames tend to look more traditional, while blue or multi-color settings suit modern rooms but may appear less natural. For a convincing display, use moderate flame brightness and low-to-medium ember lighting. Maximum brightness can flatten the contrast between the flames, logs, and background, especially when viewed near eye level while seated.
