Electricity cost calculator

Estimate energy use and cost from power and time or from measured kilowatt-hours.

Power
Days
Hours per day
h
Price per kWh
/kWh

Estimated cost in the tariff currency

Enter your price per kWh

Read explanation below

From appliance power to an estimated cost

A plug and clock leading through an electricity meter to a stack of cost tokens

Enter an appliance's power and operating time, or use energy already measured in kilowatt-hours. The calculator multiplies each energy amount by its price and returns the estimated cost in the same currency as the rate you entered.

Choose the input that matches what you know

Power-and-time mode is useful before using or buying a device. Pick watts or kilowatts, enter daily operating hours and choose a period of 1 to 366 days. For a single tariff, energy use follows this model:

E=PkW⋅h⋅d\displaystyle E=P_{\mathrm{kW}}\cdot h\cdot d

Here EE is energy in kWh, PkWP_{\mathrm{kW}} is power in kilowatts, hh is hours per day and dd is days. If power is entered in watts, the calculator divides it by 1000 first.

The measured-energy mode is better when a bill register, smart plug or meter already provides kWh. The distinction matters: watts and kilowatts measure power at a moment, while watt-hours and kilowatt-hours measure energy over time. The U.S. Energy Information Administration's guide to measuring electricity gives the same definitions and conversion.

Keep every tariff zone separate

With one rate, cost is simply energy multiplied by the price per kWh. With two or three zones, calculate each zone first and add the amounts:

C=∑iEiTi\displaystyle C=\sum_i E_iT_i

EiE_i is the energy assigned to a zone and TiT_i is that zone's price per kWh. The effective average price is the total cost divided by total energy. Do not enter a provider's clock schedule from memory; use the zone names and rates printed on the bill, account or contract.

A 1 kW device running for 2 daytime hours and 1 nighttime hour on each of 30 days uses 60 kWh by day and 30 kWh by night. At rates of 7 and 3, the two parts cost 420 and 90, for a total of 510 in the tariff currency. The effective average price is 5.667 per kWh.

Three ways to check the estimate

A portable heater. A 1500 W heater running for 2 hours a day over 30 days uses 90 kWh. At a rate of 6.5 per kWh, the estimate is 585. A thermostat may reduce actual running time, so this is an upper-bound style estimate if the heater cycles off.

A measured monthly total. A smart plug reports 250 kWh. At 6.5 per kWh, the result is 1625. No wattage or operating-hour assumption is needed because energy has already been measured.

Three tariff zones. A 1000 W load runs one hour in peak, shoulder and night periods each day for 30 days. Every zone receives 30 kWh. At rates of 7, 5.5 and 3, the costs are 210, 165 and 90, giving 465 in total and an average of 5.167 per kWh.

Nothing used. Measured consumption of 0 kWh gives a cost of 0. Zero is valid in measured mode; a zero power rating is rejected because it does not describe an operating appliance.

Why the bill can still be different

Nameplate power can be a maximum rather than an average. Refrigerators, heaters, ovens, air conditioners and chargers cycle or vary their load. A meter measured over a typical period usually gives a better estimate for those devices.

The calculator includes only energy multiplied by the rates you provide. It does not add fixed charges, taxes, demand charges, tier thresholds, penalties, rebates, net metering or supplier-specific rounding. It also does not decide when a day, night, peak or shoulder period begins.

The watt is the SI unit of power and corresponds to one joule per second, as documented in the current BIPM SI Brochure. This unit relationship supports the energy arithmetic, but the result is not an electrical safety check. Cable size, current, protective devices and local electrical rules require a separate calculation.

Questions about electricity cost estimates

These answers clarify which input to use, how zones combine and what the final number does not include.

What is the difference between kW and kWh?

A kilowatt measures power. A kilowatt-hour measures energy: a 2 kW device running for half an hour uses 1 kWh.

Should I enter the maximum power from the label?

Use it for a cautious estimate when no measured average is available. Cycling or variable-load equipment often consumes less than maximum power over a full period.

Can I use any currency?

Yes. Enter every tariff rate in one currency. The cost and zone totals use that same currency, so no exchange rate is needed.

How do day and night tariffs combine?

Multiply daytime kWh by the daytime rate and nighttime kWh by the nighttime rate, then add the two costs. The calculator also reports the effective average price.

Can tariff-zone hours add up to more than 24?

No. Each value is daily operating time, so the visible zone hours together may not exceed 24.

Does the calculator reproduce my final bill?

No. It estimates the energy portion from your inputs. Fixed charges, taxes, thresholds, credits and provider rules are outside the calculation.

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