Gas insert · Duluth Forge

Duluth Forge FNF300T Gas Fireplace Insert

Gas insert, up to 1,350 sq ft, 26,000 BTU/h

Heats up to (maker)
1,350 sq ft
Heat output (maker)
26,000 BTU/h
Efficiency (maker)
99.9%
Fuel
Natural Gas
Venting
no venting required
Thermostat
smart thermostat
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In short

Built for clean-venting room heat.

Wins
26,000 BTU/h.
Gives ground
Needs a vent route.
Suits
Clean-venting room heat.

Updated October 2026

What you get

The Duluth Forge FNF300T Gas Fireplace Insert is a gas insert that its maker rates at 26,000 BTU per hour and says heats up to 1,350 square feet.

Makers rate heating area in their own conditions, so read 1,350 square feet as a ceiling; the size calculator lists the closest fits for your space.

At full fire it burns about 25 cubic feet of natural gas an hour (its 26,000 BTU/h divided by EIA's heat content for each fuel).

As a vented unit it sends its exhaust outside through the vent system its manual lists, so it leaves room air alone; the vent route has to suit the house.

Fuel, per the listing: Natural Gas. Never connect a gas heater to a fuel it isn't set for.

Ignition: Piezo ignition.

Also on the listing: overall dimensions of 13.9 in (D) x 29.1 in (W) x 23.9 in (H).

The figures, from the maker

Each figure is the maker's or the listing's own, with its source marked. A figure the maker doesn't give is shown as not stated.

Model numberFNF300TRetailer
PowerGas PoweredRetailer
Dimensions (seller)13.9"D x 29.1"W x 23.9"HRetailer
Mounting / installationBuilt-inRetailer
Heat output (maker)26,000 BTU/hRetailer
Features (seller)Safety Shut OffRetailer
Batteries1 AAA batteries required.Retailer
Model nameFNF300TRetailer
Heats up to (maker)1,350 sq ftRetailer
Efficiency (maker)99.9%Retailer
Ventingno venting requiredRetailer
FuelNatural GasRetailer
Thermostatsmart thermostatRetailer
IgnitionPiezo ignitionRetailer

Is it the right heater for the room?

Pick it when

  • Clean-venting room heat
  • Homes with gas or propane
  • Heat without electricity

Pass on it when

  • Homes without a vent route
  • Homes without gas or propane

Where it wins, where it gives ground

Wins

  • 26,000 BTU/h
  • Exhaust vented outside
  • Natural Gas
  • Works in a power cut

Gives ground

  • Needs a vent route
  • Needs a gas line

Know before you install

  • Figures are the maker's own and are rated in the maker's conditions. Installation, venting, chimney, gas and electrical work follow the manual and local code, carried out by a qualified installer.

Heaters to weigh against it

Other gas stoves, fireplaces and inserts in the same heat range

Every gas stoves, fireplaces and inserts on one chart · All Duluth Forge models listed

Buying this model

The button opens this exact model's listing. Prices and stock change, and installation parts are usually sold separately; check the box contents and the manual's venting list before you order.

Prices change often; the button shows today's price.

Each button opens this exact model. We may earn a commission on tracked links; it never changes what we publish. Disclosure

Questions about this model

How much gas does the Duluth Forge FNF300T Gas Fireplace Insert use?
At full fire, about 25 cubic feet of natural gas an hour, from its 26,000 BTU/h rating and EIA's heat contents; lower settings use less.
Does the Duluth Forge FNF300T Gas Fireplace Insert need a vent or chimney?
Yes: it vents outside through the system its manual lists.

Bottom line

Built for clean-venting room heat.