Electric Fireplace for Your Existing Fireplace

If you have an existing masonry or prefabricated fireplace that sits unused, produces more smoke than heat, or simply feels outdated, an electric fireplace insert is one of the most practical and cost-effective upgrades you can make. Unlike gas or wood alternatives, an electric insert requires no chimney liner, no gas line, and no major structural renovation. You get instant ambiance, optional supplemental heat, and a dramatically improved look — often in under an hour of installation.

This guide walks you through every consideration: sizing, venting myths, safety, efficiency, and the best product categories for different room layouts. Whether you want a realistic flame effect, a heater that actually warms your space, or a complete makeover of a dated hearth, the information below will help you choose with confidence.

Why Choose an Electric Insert for an Existing Fireplace?

Electric Insert vs. Other Options for an Existing Fireplace

For a deeper comparison across all fuel types, read our electric vs gas vs wood fireplace comparison. If you are specifically replacing a wood-burning unit, you may also want to explore converting a wood-burning fireplace to electric.

How to Choose the Right Size Electric Insert

Sizing an electric insert for an existing fireplace involves two measurements: the opening dimensions of your fireplace and the heating capacity you need for the room. Getting both right ensures a flush, built-in look and comfortable warmth.

• Measure Your Fireplace Opening Measure the width, height, and depth of the existing firebox. Most electric inserts are designed to fit standard openings, but you may need a trim kit or surround to cover gaps. For a seamless look, consider an insert with an adjustable surround.
• Calculate Your Heating Needs Use our BTU and heating capacity guide to estimate the wattage required for your room size. As a rule of thumb, a 1,500-watt electric heater can warm up to 400 square feet, while larger units may claim up to 1,000 square feet under ideal conditions.
• Decide on Flame Technology LED flame effects are energy-efficient and low-maintenance. Water-vapor (or "vapor") flames are more realistic but require a water reservoir and occasional refilling. For the most authentic look, see our roundup of realistic-looking electric inserts.
• Consider Additional Features Remote controls, thermostats, crackling sound effects, and multi-color flames add convenience and atmosphere. If you want a heater that maintains a consistent temperature, look for a model with a built-in thermostat.

Installation Overview: What to Expect

Installing an electric insert into an existing fireplace is straightforward, but a few preparation steps ensure a safe and professional result.

• Clean and Inspect the Firebox Remove any ash, debris, or old log holders. Check for loose bricks or damaged panels. If the fireplace has a gas line, have it capped by a professional before proceeding.
• Ensure Power Access You will need a standard grounded outlet near the fireplace. If none exists, consult an electrician to install one. Avoid using extension cords for permanent installations.
• Slide the Insert into Place Most inserts are designed to slide directly into the opening. Adjust the leveling feet if included, and secure the unit according to the manufacturer's instructions.
• Attach the Surround or Trim A surround covers the gap between the insert and the fireplace opening. Many models include a custom surround, or you can purchase a decorative fireplace surround for electric fireplace separately.
• Test the Unit Plug in the insert, test the flame effect, heater, and remote control. Make sure the unit is stable and that no cords are pinched.

For a more detailed walkthrough, see our guide to installing an electric fireplace into an existing fireplace. If you are replacing a wood-burning unit specifically, the process is similar — see electric fireplace insert into wood burning fireplace.

Safety, Efficiency, and Maintenance

Electric inserts are among the safest fireplace options available. They produce no carbon monoxide, no open flame, and no creosote. However, a few best practices keep your unit running efficiently for years.

Frequently Asked Questions