MultiConvers

Electricity Cost Calculator

Estimate what one run of a heater, kettle or charger costs from its wattage, the hours it is on, and the unit price on your bill — a planning figure, not the invoice.

Updated

How to use

  1. Enter power from the nameplate. Choose watts or kilowatts to match the label.
  2. Enter how many hours this session lasts. A kettle that boils for 3 minutes is 0.05 hours.
  3. Enter the unit price per kWh from your bill, in the same currency you want the cost in.
  4. Read kWh and cost. For a month of daily use, use the appliance calculator instead of guessing hours.

How it works

A kilowatt-hour is one kilowatt running for one hour. Power on a kettle might be 2,200 W, which is 2.2 kW. Three minutes is 0.05 h, so energy is 2.2 × 0.05 = 0.11 kWh. At 0.25 per kWh that boil costs about 0.03 in the currency you used for the price.

A 1,000 W space heater for two hours is 2 kWh. At 0.20 per kWh the session is 0.40. Running it every evening for 30 days is 60 kWh and 12.00 at the same rate — but only if the heater really ran two hours each day at full power. Thermostats cycle; the nameplate is a maximum, not a guaranteed draw.

The price you type should be the energy unit rate, not the whole-bill average unless you want a rough blend. Standing charges, taxes, time-of-use peaks and feed-in credits are not modelled. A night rate and a day rate need two runs of this calculator.

A Swedish bill splits that rate further. Retail energy (elhandel), the local grid’s per-kWh transfer fee and energy tax are separate lines. The grid subscription is a fixed monthly amount and does not belong in a single session. Add only the per-kWh lines you want, in the currency on the invoice. Example, not a tariff: 0.80 retail + 0.30 grid transfer + 0.40 energy tax = 1.50. A 2 kW heater for 2 hours is 4 kWh and costs 6.00 at that rate. A 200 subscription is extra, whether the heater ran or not. VAT is not added unless you fold it into the 1.50. Finnish and Åland invoices use the same split — a local grid fee is not the retail price — and this page does not store those tariffs.

Hours are this use only. Do not enter 720 for a month unless the device actually ran 720 hours. The appliance-energy tool is built for hours per day and days per month.

EV charging at 7 kW for 3 hours is 21 kWh before charger losses. The dedicated EV tools add efficiency and battery percent. This page is the raw power × time × price identity.

Formula

kW = watts ÷ 1000 (when power is in W)
kWh = kW × hours
Cost = kWh × price per kWh

Worked examples

  • A 1 kW heater for 2 hours

    1000 W, 2 h, 0.20 / kWh → 2 kWh, cost 0.40

  • A 1.5 kW load for 4 hours

    1.5 kW, 4 h, 0.30 / kWh → 6 kWh, cost 1.80

  • Per-kWh lines on a Nordic bill, not a live tariff

    2000 W, 2 h, 1.50 / kWh (0.80 + 0.30 + 0.40) → 4 kWh, cost 6.00, fixed subscription excluded

Useful notes

  • Not a utility bill. The fixed grid subscription, VAT and time-of-use bands are omitted unless you fold them into the rate.
  • Nameplate watts are often a maximum, not the average draw.
  • For daily hours over a month, use Appliance Energy Cost.

FAQ

How do I calculate electricity cost from watts?

Convert watts to kW (÷ 1000), multiply by hours for kWh, then multiply by your price per kWh.

Should I enter watts or kilowatts?

Either. Nameplates often show watts; EV chargers and larger loads are often in kW. Pick the matching unit.

Does this include standing charges?

No. It only multiplies energy by the unit price you enter.

How do I cost a 3-minute 2,200 W kettle?

2,200 W is 2.2 kW. 3 minutes is 0.05 h. Energy is 0.11 kWh. Multiply by your price per kWh.

Should I use the average price on the bill?

Use the unit rate if you have it. The average of the whole bill includes standing charges and will overstate a single appliance. On a Swedish bill, add the per-kWh lines and leave the fixed grid subscription out.

How a Nordic bill is split

Guides

Related tools

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