How this is calculated
Inspect the versioned inputs.
| Constant | Value | Scope & source |
|---|---|---|
| tariff | 0.1816 USD/kWh | August 2026 U.S. residential monthly average; released October 23, preliminary. User tariff override should be prominent. eia-residential-2026-08 ↗ Verified 2026-11-08 |
| weeksPerYear | 52 weeks/year | Planning convention: 52 use-weeks per year; editable actual attendance belongs in frequency. editorial-tool-method ↗ Verified 2026-11-08 |
Input defaults that are not sourced measurements are illustrative planning assumptions. Exact unit definitions, the 52-week convention and algorithm details are in the shared methodology.
Worked example
An example you can inspect.
At 6 kW for a full-power hour, energy is 6 kWh. The August 2026 U.S. residential average of $0.1816/kWh gives $1.0896; local rates and actual cycling can differ.
Use equipment values, not a type label.
Enter the actual rated power for each electric device. The traditional and infrared labels provide comparison context; they do not assign equivalent heat exposure or a universal power demand. Check the product nameplate or manual and distinguish its electrical input from any marketing description. A comparison is only as useful as its entered time and power assumptions. If a device has several operating modes, prepare a separate scenario for the mode you expect to use.
Separate warming from occupied time.
The example assumes full rated power during the entered preheat interval. During occupied time it multiplies rated power by your duty fraction. A fraction of one means continuous rated input during that interval, while a lower fraction represents an assumed average operating share. This is a simplified accounting model. It does not simulate thermostat cycling, building heat loss or standby consumption. Use a measured operating record to refine those inputs where available, keeping the room, weather and usage conditions with the measurement.
Check the bill basis before comparing totals.
The default national residential tariff is a dated EIA observation, not your household's contract. Replace it with a relevant local energy rate and review how taxes, fixed charges or time-of-use pricing affect the comparison. The tool multiplies energy by the entered tariff and does not allocate every charge on a utility bill. Annual cost also assumes the entered visits per week throughout the stated fifty-two-week convention. A seasonal routine or holiday closure needs a different assumption.
Keep the wood scenario in its own units.
In wood mode, enter the quantity of fuel used per visit and its price per matching unit. If the quantity is in kilograms, the price must be per kilogram; a price per bag needs a quantity expressed in equivalent bags. The calculator does not infer moisture content, combustion efficiency or a conversion between a purchased load of wood and electric kilowatt-hours. Its result is direct fuel-cost arithmetic. It excludes labour and any other unentered ownership costs, which belong in the separate ownership worksheet.
Questions, considered
Questions about this tool
How should I interpret the running cost calculator result?
The EIA average is dated, preliminary and not your utility quote. Duty cycle and preheat duration are assumptions; nameplate power multiplied by all elapsed time is not measured consumption. Estimate electric or wood-fuel running costs from power, time, cycling, frequency and your tariff, then compare entered equipment scenarios.
Which assumptions matter in the running cost calculator?
Electric kWh/session = kW × (preheat minutes + session minutes × duty fraction) / 60. Preheat assumes full power. Multiply kWh by entered USD/kWh, then by sessions and 52 planning weeks. Traditional and infrared each use their own entered nameplate power. Wood fuel cost = entered fuel quantity/session × price/unit. No fuel-efficiency equivalence is inferred.
Primary sources
Follow the source.
- EIA Electric Power Monthly, Table 5.3 ↗
Year 2026, August, Residential column; release October 23, 2026; technical notes
U.S. residential average 18.16 cents/kWh for August 2026. Latest available monthly observation on review date; 2026 values preliminary. National average revenue per kWh is a proxy and differs from a household's marginal tariff.
Checked 2026-11-08 - Virginia Cooperative Extension: Estimating Appliance and Home Electronic Energy Use ↗
Estimating Energy Consumption
Energy is watts multiplied by operating hours divided by 1000; multiply kWh by the utility rate for cost. Heater cycling requires actual energized time or an explicitly user-supplied duty factor.
Checked 2026-11-08 - Harvia — FAQ about the energy consumption of sauna bathing ↗
Section2: How much energy does the heater consume?
A manufacturer example for a properly sized heater in an insulated room. Thermostat cycling means nameplate kW multiplied by clock time is an upper-bound scenario, not guaranteed consumption.
Checked 2026-11-08