How to Install Electric Fireplace Insert? | DIY Installation

Converting a wood-burning fireplace to an electric insert gives you heat and ambiance without the ash, creosote, or chimney sweeping. The process follows a clear sequence: measure the opening, seal the chimney against drafts and rain, slide the insert in and level it, connect power, and attach the trim. Each step matters, but none are especially difficult when you follow the right order. You will need a tape measure, level, drill, shims, and basic hand tools — nothing specialized.

Electric inserts are popular because they deliver steady heat with a realistic flame effect while requiring no gas line, venting, or structural changes to your home. Because they produce no combustion gases, the chimney seal is purely for energy efficiency and moisture protection rather than safety. The installation work is almost entirely preparation: getting the opening ready and making sure the insert fits snug and level.

How Do You Measure for an Electric Fireplace Insert?

Measure the height, width, and depth of your existing firebox opening before you buy anything. This is the most common installation mistake — an insert that does not fit the opening is unusable, and returns on large appliances are rarely free. Use a steel tape measure and take each dimension at the narrowest point of the opening, since masonry fireboxes are rarely perfectly square.

The insert needs to be slightly smaller than the opening so it slides in easily, with the surround or trim covering any visible edge gaps when installed. Heat & Glo’s instructions note that the back of the insert should be a bit narrower than the measured dimensions for a proper retrofit fit. Depth is especially easy to overlook — the insert needs enough room at the back for the heating element and airflow, so do not skip that dimension. If your opening dimensions fall outside standard insert sizes, consider a smaller unit with an oversized trim panel to bridge the gap. Write down your exact numbers and compare them against the product specs of any model you consider.

Once you know your opening dimensions, browse our tested roundup of the best electric fireplace log inserts to find a unit that fits your space and budget.

Prep the Firebox and Seal the Chimney

Clear out ash, soot, and debris from the firebox before bringing the insert in for a test fit. If the fireplace has been used recently, wait long enough that no hot embers remain. MagikFlame warns against vacuuming ashes until you are certain every ember is cold — hot ash can damage a vacuum or start a fire inside the bag. If you are converting from a gas fireplace, ensure the gas line is capped or removed by a professional before proceeding.

Sealing the chimney is the most important preparation step. Close the damper and seal the flue opening to stop cold drafts and rainwater from entering the firebox. Heat & Glo recommends using non-fibrous installation materials for sealing around the insert — mineral wool or fireproof caulk are good options — and MagikFlame suggests adding a cover plate on top of the chimney to block water entry entirely. A properly sealed chimney keeps your electric fireplace working efficiently and prevents moisture damage inside your home. Check the seal once you slide the insert in place and feel around the edges for any air movement.

Slide In, Level, and Connect Power

Center the insert in the firebox opening so the front sits flush against the surround. Use the leveling brackets or shims included with your unit to get the insert perfectly level both side to side and front to back. A tilted insert looks unprofessional and may cause uneven heat output or operational issues. Adjust the brackets a little at a time and check the level after each turn — small adjustments make a visible difference.

Most electric fireplace inserts plug into a standard 120-volt household outlet. If an outlet is already inside the firebox, plug the unit in directly for a clean look with no visible cord trailing outside. If there is no outlet inside, route the cord through the firebox gap to a nearby outlet outside the fireplace. Some installers add a new outlet inside the firebox during the prep phase for the cleanest result. For built-in or recessed models that require hardwiring, hire a licensed electrician to prepare a dedicated circuit that meets your local electrical codes and the manufacturer’s amperage specifications. ElectricFireplacesDirect recommends confirming the voltage and amperage requirements before starting the installation.

Test the unit before you install the front trim. Heat & Glo’s installation instructions recommend verifying the flame effect, heater, and remote control all function while the unit is still accessible. Run the heat for a few minutes to confirm airflow and thermostat behavior, and check that the remote pairs correctly. Once everything checks out, attach the front surround and trim. The attachment method varies by model — some use hooks and magnets, others use screws or a snap-fit system. Follow the manual that came with your specific insert.

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