Clear inputs. Clear maths.

WattPeek uses your inputs to estimate the variable electricity cost of running an appliance. It does not retrieve current tariffs or claim to predict your entire bill.

Power-based calculation

daily kWh = watts ÷ 1,000 × hours × quantity × active time ÷ 100

Daily cost = daily kWh × unit price. Period cost = daily cost × entered days. Annual cost = daily cost × 365.

Measured energy

Enter kWh consumed per day or session. Multiply by quantity, unit price and the number of days or sessions in your chosen period. The annual figure assumes one identical session every day for 365 days. Cost per hour is not shown in this mode, because session length is not provided.

Active time

Use 100% if you entered average power. Only reduce the active-time percentage if you entered on-state power and know the proportion of time the appliance draws that power. Do not adjust both average power and duty cycle for the same on/off behaviour.

Rates and currencies

Country presets use a bundled Eurostat nrg_pc_204 snapshot retrieved on 1 November 2026: H1 2026 household prices for consumption band 2,500–4,999 kWh/year, including all taxes and levies. The 39 available country/territory presets are in EUR per kWh, including countries whose national currency is different. These are published averages, not live tariffs or exact marginal rates. The snapshot does not update itself. Replace it with newer verified data when available. You may override any preset with your own per-kWh rate, including applicable per-unit taxes. Enter whole currency units, for example 0.25 for 25 cents. Currency selection changes formatting only; it does not convert values. Fixed standing charges are excluded. For multiple time-of-use rates, calculate each period separately. Tiered tariffs require the appropriate marginal rate.

Preset values

Appliance values are editable illustrations, not manufacturer specifications or measured population averages. Gaming-PC PSU capacity is not actual input power. For cycling appliances and full-cycle devices such as dryers, measured kWh is preferable to maximum wattage.

Lists and comparisons

The list sums the selected period cost of each entry and separates currencies. Entries with different periods are flagged. Savings assume a proportional reduction in energy consumption, with everything else equal. This may not represent equal heating, cooling or cooking performance.

Rounding

Calculations retain their numeric precision until display. Currency results show two decimal places; energy is displayed with up to three decimal places. Very small positive costs can display as 0.00. Annual values use 365 days, not 12 times the selected period.