If you have an existing fireplace opening sitting unused, an electric fireplace insert for an existing fireplace is one of the most practical upgrades available. You keep the mantel and surround, avoid any venting or gas work, and end up with a functional focal point that provides both ambiance and supplemental heat. Getting the right result depends on measuring correctly, matching the insert type to the opening, and understanding the installation requirements before you order. This guide covers each of those decisions.
There are three main configurations, and each suits a different scenario.
Built-in insert
A self-contained firebox unit that slides into the existing opening and mounts flush or recessed into the framing. These are designed for permanent installation and connect to a dedicated 15-amp circuit. They include a metal frame with a trim kit to close the gap between the unit and the surrounding masonry or drywall. The SimpliFire Traditional Electric Fireplace Insert and the Amantii Traditional Built-In Electric Fireplace Insert are both built-in formats with plug-in and hardwire options.
Flush-mount insert
A specific style of built-in where the unit sits at the same plane as the fireplace surround. The Sierra Flame INS-FM-30 Flush Mount Electric Fireplace Insert includes a black steel overlay and surround that close the visible gap between the unit and the existing opening, giving a finished look without custom millwork.
Electric log set
A standalone log set that sits on the hearth inside the existing firebox. No framing, no trim kit, and no dedicated circuit required. The Dimplex Revillusion Plug-In Electric Log Set is the simplest option in this category: place it in the opening, plug it into a 120V outlet, and it operates immediately. Revillusion ThruView technology uses a partially frosted acrylic panel to eliminate reflections, so the flames appear to rise from within the logs rather than off a reflective surface.
Get these three measurements before selecting a product.
Width: The primary filter. Most built-in inserts are available in multiple width options. The Amantii Traditional comes in six sizes from 26 to 48 inches. The Modern Flames Redstone line runs from 26 to 54 inches. Match the insert width to the interior opening width, not the surround.
Height: Verify the insert height does not exceed the interior opening height. Manufacturers list the overall unit dimensions in their specifications.
Depth: The most frequently overlooked dimension. Most built-in electric inserts require a minimum firebox depth to fit. The Modern Flames Redstone 36" Built-In Electric Fireplace Insert requires approximately 9 7/8 inches of depth. The Dimplex Revillusion RLG20 log set requires at least 12.5 inches of depth. Measure front-to-back at the narrowest point of the firebox before ordering.
For wood-burning masonry fireplaces, depth is rarely a constraint since most masonry boxes run 12 to 20 inches deep. For factory-built zero-clearance fireplace boxes, depth is often tight. If the existing opening is under 10 inches deep, an electric log set is likely the only workable option.
Most 120V electric inserts operate at approximately 5,000 BTU and provide supplemental heating for 400 to 500 square feet.
Specific figures from the product specifications: the Amantii Traditional, Modern Flames Redstone, and SimpliFire Traditional each produce 5,000 BTU at 120V. The Sierra Flame INS-FM-30 outputs 4,800 BTU. The Dimplex Revillusion log set is rated at 5,118 BTU with a fan-forced ceramic heater.
If you need greater output, the Amantii Traditional supports optional 240V hardwiring, which raises heat output to 10,230 BTU and extends supplemental heating coverage to approximately 900 square feet. This requires a 240V dedicated circuit and a licensed electrician for installation.
Electric inserts are supplemental heaters. They work alongside your existing HVAC system rather than replacing it as a primary heat source for large or poorly insulated spaces.
All inserts in this range include a flame-only mode that operates the visual effect without activating the heater, which makes year-round use practical in warmer months.
Plug-in (120V): The simplest option. An existing standard outlet inside or near the firebox is sufficient. The Dimplex Revillusion log set is plug-in only. Most built-in inserts also offer a plug-in option, though the power cord will be visible unless routed through the wall.
Hardwire (120V): Requires a licensed electrician to run a dedicated 15-amp circuit. Eliminates the visible power cord and provides a permanently built-in appearance. The Sierra Flame INS-FM-30, Amantii Traditional, SimpliFire Traditional, and Modern Flames Redstone all support this.
Hardwire (240V): Available on the Amantii Traditional only. Requires a dedicated 240V circuit and significantly increases heat output. The right choice for rooms where 5,000 BTU is not sufficient.
If you are retrofitting an existing gas fireplace, the gas line must be capped by a licensed plumber or gas technician and the damper permanently sealed before installing an electric insert. These steps are separate from the insert installation itself.
Traditional interiors: The SimpliFire Traditional uses brick side panels, glowing log sets, and ember effects to replicate the look of a wood-burning hearth. Its self-trimming design reduces finishing work, and the unit is available in 25", 30", and 35" widths. The Amantii Traditional includes birch logs, multi-color canopy lighting with 13 color options, and an optional crackling sound effect.
Contemporary or minimalist interiors: The Modern Flames Redstone uses Hybrid-FX Flame Technology that allows independent control of the flame color, ember bed, and downlighting. A cool-top design directs heat forward rather than upward, making installation beneath a television safe. It is available in five widths from 26 to 54 inches and includes two trim kit sizes.
Realistic log presentation: The Dimplex Revillusion uses a frosted acrylic panel with ThruView technology to eliminate reflections. The flames appear to rise from within a full grate of hardwood-cast logs, which is closer to the visual of an open wood fire than a framed insert.
Browse the full range at The Fireplace USA electric fireplace inserts collection. For wall-mounted and built-in formats beyond inserts, see the electric fireplaces collection.
Most wood-burning masonry fireplaces and non-functioning decorative fireplaces can accept an electric insert, provided the opening is deep enough and electrical access is nearby. Gas fireplaces require the gas line to be capped and the damper permanently sealed before an electric insert can be installed. Consult a licensed professional before modifying any gas appliance.
No. Electric inserts produce no combustion and require no venting, flue access, or open damper. Once an electric insert is in place, the damper on an existing wood-burning fireplace can be permanently closed.
Measure the interior width, height, and depth of the firebox. Width determines which unit size will fit. Depth is the most critical constraint: most built-in inserts require at least 9 to 10 inches of depth, while log sets typically need at least 12 to 13 inches. Measure at the narrowest point of the firebox, not the front face opening.
A plug-in insert connects to a standard 120V wall outlet with no electrical work required. A hardwired insert is wired directly to a dedicated circuit by an electrician, eliminating the power cord and providing a permanently built-in appearance. Heat output is equivalent at 120V. Hardwiring at 240V, available on the Amantii Traditional, substantially increases output.
Most 120V electric inserts produce between 4,800 and 5,118 BTU, suitable for supplemental heating in spaces up to 400 to 500 square feet. The Amantii Traditional's optional 240V hardwire configuration produces 10,230 BTU, covering up to approximately 900 square feet.
Yes. All inserts covered here include a flame-only mode that runs the visual effect without activating the heater. This lets you use the fireplace for ambiance year-round without raising room temperature.
Monessen builds vent-free gas fireplaces in the United States, with a reputation for realistic log flame and straightforward installation. This guide covers Natural Blaze Technology, who each model serves, and which Monessen fireplaces are available at The Fireplace USA.
A direct vent gas fireplace draws combustion air from outside and exhausts all gases back out through a sealed two-pipe system, keeping indoor air clean. This guide covers venting options, BTU sizing, traditional vs. linear styles, and the best models to consider in 2026.
{"one"=>"Select 2 or 3 items to compare", "other"=>"{{ count }} of 3 items selected"}
Leave a comment