Yes, you can put an electric fireplace insert in an existing fireplace that no longer works. An electric or water vapor insert sits inside the old masonry opening, needs no gas line, chimney or venting, and runs on household power. For a prewar apartment or brownstone with a sealed or decorative fireplace, it is often the simplest way to bring real-looking fire back to the room.
This guide covers how to tell whether your opening will take an insert, how to measure it, what to do about the chimney and the power, and which electric and water vapor models we recommend for traditional New York interiors.
Key takeaways
- A non-working fireplace makes an ideal home for an electric insert, because the opening, hearth and mantel are already there.
- Measure the opening's width, height and depth at the narrowest points, then compare them to the manufacturer's framing dimensions, not the unit's overall size.
- An open flue should be capped or blocked to stop drafts, which matters even more for water vapor flames. Confirm with a qualified contractor before anything is sealed.
- Most inserts can run on a standard 120 volt circuit; a dedicated circuit is often recommended, and hardwired 208 or 240 volt connections require a licensed electrician.
- Choose between a heating firebox with realistic logs and a water vapor cassette that shows flame and smoke but produces no heat.
Why so many New York fireplaces sit dark
Walk through enough Upper East Side classic sixes, Park Slope brownstones and West Village townhouses and you find the same thing: a beautiful carved mantel framing a fireplace that has not been lit in decades. Some flues were sealed during earlier renovations, some buildings no longer permit wood burning, and in many co-ops a damaged or shared chimney makes restoration impractical.
Wood burning is heavily restricted in New York City, and vent-free gas appliances are not permitted in NYC residences. That leaves two realistic paths for a dark fireplace: a vented gas insert, which needs a sound, relined chimney and a licensed master plumber, or an electric insert, which needs neither. We cover the gas route in our guide to converting a brownstone fireplace to gas. For many apartments, electric is the path that actually gets built.
Will an electric insert fit my fireplace opening?
An electric insert fits when the masonry opening is at least as large as the manufacturer's framing opening in all three directions. Dimplex's own guidance is direct: measure the width, height and depth of the existing opening before ordering, and make sure the insert clears the interior on all three sides.
How to measure
- Width: measure across the front of the opening and again at the back wall. Masonry fireboxes usually taper, so the back is often narrower.
- Height: measure from the hearth floor to the underside of the lintel at the front, and again at the back if the firebox slopes forward.
- Depth: measure from the face of the opening to the back wall at hearth level and at the top. Use the smallest figure.
- Check the damper and smoke shelf: an open damper or protruding throat can reduce usable height.
Small Victorian coal fireplaces, common in brownstones, are often shallow and narrow. Those openings tend to suit a compact cassette, while a larger prewar opening can take a full-size firebox. Our guide on how to measure a fireplace opening walks through the process in more detail.
What if the opening is larger than the insert?
That is normal. The gap between the insert and the masonry is closed with a trim kit or a custom panel in a finish that suits the room. Ask your installer to confirm the approach for the exact model, since some fireboxes have cosmetic flanges only and rely on the surround for a finished edge.
What should I do about the chimney?
Cap or block an open chimney before installing an electric insert. Electric units produce no combustion, so they need no venting, and an open flue simply pulls warm room air up and lets cold drafts down. Dimplex notes that an unused chimney is usually capped or blocked off during installation for this reason, and advises checking with a qualified contractor before sealing any flue.
In a co-op or condominium, the chimney may be a shared building element. Speak with your managing agent before anyone caps, blocks or alters it. Drafts matter even more for water vapor fireplaces, whose mist flames can be disturbed by moving air; Dimplex specifies a draft barrier for its Opti-myst cassettes in drafty locations.
What kind of power does an electric fireplace insert need?
Most electric inserts run on 120 volt household power, and many can simply plug in. The catch in an old fireplace is that there is rarely an outlet inside or near the firebox. Plan for one of three solutions: a new outlet placed discreetly inside or beside the opening, a cord routed to a nearby outlet, or a hardwired connection.
Manufacturers often recommend a dedicated circuit, and some models offer higher heat output when hardwired at 208 or 240 volts. Any new circuit or hardwired connection should be installed by a licensed electrician to local code, and in many co-ops new wiring is treated as an alteration, so check your alteration agreement first.
Three inserts we recommend for traditional New York rooms
Each of these is an electric unit with no gas line or flue, chosen because it suits the proportions and character of a prewar or brownstone fireplace.
Dimplex Revillusion 42 inch built-in firebox (REV42-BL)
The Dimplex Revillusion REV42-BL is the choice for a generous opening where realism and heat both matter. Its Realogs are handcrafted from real wood and lit from within, and a reflective panel makes the flames appear to rise from inside the log set over an ember bed of tumbled glass and black gravel.
- Framing opening: 42-5/8 in wide, 30-5/8 in high and 12-1/2 in deep, per Dimplex
- Heat: about 4,436 BTU at 120V, rising to about 8,786 BTU when hardwired at 240V
- Plug kit included for 120V use; Dimplex recommends a dedicated 15 amp circuit
- Heat can be turned off for flame-only evenings
Amantii Traditional Bespoke 38 inch built-in insert
The Amantii Traditional Bespoke 38 is shaped like a classic wood fireplace opening, with a tall 35-1/4 by 23-5/8 inch viewing area that sits comfortably beneath a period mantel. Amantii offers square, arch, 3-sided and 4-sided trim, and the arch option is a natural match for the rounded openings found in many older homes.
- Appliance: 37-1/8 in wide, 27-1/4 in high and 12-3/8 in deep
- Power: 120V, 1,465 watts, rated for up to 400 sq ft
- Adjustable flame color, height and speed, with the heater independent of the flame
- Amantii specifies at least 3 ft of clearance in front of the glass
Dimplex Opti-myst Pro 500 water vapor cassette (CDFI500-PRO)
For a small brownstone fireplace or anyone who wants the look of flame and smoke rather than heat, the Dimplex Opti-myst Pro 500 is the most convincing option in a compact footprint. It creates flames from an ultrasonic mist lit by LEDs, so there is no hot glass, and the effect is cool enough to reach into.
- Cassette: 20-1/8 in wide, 12 in deep and 9 to 9-1/2 in high
- Framed opening: 20-3/8 in wide and 12-1/4 in deep with the media plate, or 14-1/4 in with the log set
- 42 oz water container gives up to 8 hours of flame per fill; an optional plumbing kit provides a continuous supply
- Visual flame only, at 230 watts; Dimplex sells a separate heater
- Needs a 40 sq in fresh air inlet beneath the cassette and at least 16 in of clearance above the media
Where tap water is hard, Dimplex recommends softened or filtered water to keep the cassette working well. Browse more mist models in our water vapor fireplace collection, and read our water vapor fireplace buying guide for maintenance details.
Heat or ambience: which insert is right for you?
Choose a heating firebox if the fireplace anchors a living room you use on winter evenings and you want warmth along with the flame. Choose a water vapor cassette if the opening is small, the room is already well heated, or you want the most lifelike flame and smoke effect. In a steam-heated prewar building, where radiators already keep rooms warm, the mist effect alone is often all a fireplace needs to deliver.
| Consideration | Electric firebox | Water vapor cassette |
|---|---|---|
| Heat | Fan-forced heater, can be switched off | None on the Opti-myst Pro 500 |
| Flame effect | LED flame behind glass | Lit mist with a smoke effect, no glass |
| Upkeep | Minimal | Refill water or add a plumbing kit |
| Best opening | Mid-size to large prewar openings | Small or shallow openings |
You can compare every model sized for an existing opening in our electric firebox inserts collection, or browse traditional electric fireplaces for styles suited to period rooms.
Frequently asked questions
Can you put an electric insert in a wood-burning fireplace?
Yes. An electric insert can be installed in a wood-burning fireplace that is no longer used, provided the opening meets the manufacturer's framing dimensions. Stop using the fireplace for wood once the insert goes in, and have the flue capped or blocked to stop drafts.
Do I need to close the damper or seal the chimney?
Closing or sealing the flue is recommended, because an electric insert needs no venting and an open chimney lets heat escape and drafts in. Have a qualified contractor confirm the method, and in a co-op or condo check with building management first.
Is an electric fireplace insert allowed in an NYC co-op?
Electric inserts avoid the gas, venting and combustion questions that complicate other fireplaces, which typically simplifies board review. Any new wiring may still count as an alteration, so review your alteration agreement before work begins.
Does a water vapor insert make the room humid?
A water vapor insert releases a fine mist, and the Opti-myst Pro 500 holds 42 oz of water, which Dimplex rates for up to 8 hours of flame per fill. Use softened or filtered water where tap water is hard.
Bring your fireplace back to life
A dark fireplace is one of the most rewarding rooms to finish, because the architecture is already there. If you would like help measuring your opening or choosing between a heating firebox and a water vapor cassette, book a free consultation, visit our Maspeth, Queens showroom, or call us at 718-326-4328. You can also learn more at nycfireplaces.com.