Gas and electric fireplaces each have their environmental advantages. The environmental costs and benefits of both depend on the intended use and where the local electrical utility gets its power.
Both gas and electric fireplaces eliminate the smoke from wood fires. Gas fireplaces still must be vented, since they produce carbon dioxide from natural gas combustion. However, burning natural gas produces heat more efficiently than electric heat sources, so less overall energy is needed to produce the same feeling of warmth
If the objective isn’t warmth, gas fireplaces start looking worse, since the combustion is required for the flame effect.
By contrast, electric fireplaces operate the heat and flame effects independently. Electric fireplaces are effectively an electric space heater designed to look like a burning fire. The heat is the energy-hungry function, so the ability to have flickering flames for mood without producing heat saves electricity.
Saving electricity saves emissions. Although electric fireplaces do not produce combustion emissions at the source, the electricity to power them comes from a power plant that, in the U.S., is likely to be either a coal-burning or natural gas-powered plant.
Gas and electric fireplaces each have environmental benefits and drawbacks. If you are looking for supplemental heat for a room, the gas fireplace offers a cleaner, more energy-efficient option. If you want the ambiance of a fireplace, the electric fireplace is the way to go.