An evening with heat and an evening with flames only are not the same electricity calculation. Use the exact draw for each mode, the time you expect to run it, the number of days and the rate that applies to your home. The calculator keeps the two operating periods separate, shows the kWh and cost for each one, and exposes every number used in the formula.
If your model does not publish the wattage for a mode you plan to use, leave that wattage blank. You may see a clearly marked subtotal for the known mode, but the calculator will not turn incomplete inputs into a total.
Two operating periods, not two wattages in the same hour
Enter heat-mode draw as the total power used in the selected heat setting. That figure can already include the flame effect and fan, so do not add flame-only wattage on top of it during the same hours. The separate flame-only fields are for time when the visual effect is running and the heater is off.
The two daily times therefore cannot exceed 24 hours when added together. This protects the result from counting one hour twice. If you only use one mode, enter zero hours for the other mode; its wattage then becomes unnecessary.
Match each input to a number you can defend
| Input | Best place to get it | Do not substitute |
|---|---|---|
| Heat-mode watts | The nameplate or current specification for the exact heat setting | A generic electric-fireplace wattage when your model states another draw |
| Heating-element on-time | Observed active heating time or a meter over a representative session | The full wall-clock session when the thermostat cycles the heater off |
| Flame-only watts | A mode-specific specification or suitable plug-in power meter | Heat-mode draw or an estimate copied from a different model |
| Electricity rate | The applicable rate on your utility bill or plan | A national average when your locality, tier or time period differs |
The visible arithmetic behind the result
The U.S. Energy Information Administration’s electricity guide defines one kilowatt as 1,000 watts and a kilowatthour as one kilowatt used for one hour. For each active mode, the calculator uses:
Mode cost = (watts ÷ 1,000) × hours per day × usage days × cents per kWh ÷ 100
It then adds the two mode costs only when both active modes have known wattages. The result is an estimate for the operating pattern entered, not a prediction of the full electric bill. Fixed charges, taxes, demand charges, tiered rates and time-of-use pricing can change what a bill shows. EIA’s explanation of average prices and utility rates is also why this page leaves the rate field empty instead of supplying a national default.
A thermostat changes the hours that belong in the formula
A fireplace can remain switched on while its thermostat cycles the heating element. When that happens, the heat-mode hours should represent active heating time rather than the entire session. If you cannot obtain that time from the controls or a suitable meter, run a conservative high-and-low scenario instead of inventing a precise duty-cycle percentage.
Cost does not establish whether the fireplace can warm the intended space. Use the electric fireplace heat-output and running-cost guide to connect the estimate to heater output, room conditions and the limits of supplemental heat. More measurement-based resources are listed in the electric fireplace planning tools hub.
The calculator runs in your browser. It does not send or store the wattage, hours, days or electricity rate you enter.