Appliance Electricity Cost and Solar Payback Calculator

Monthly kWh and bill for ACs, fans, fridges and pumps, plus solar size and payback. Free, private and instant.

How to use the Electricity Cost & Solar Payback

  1. Add one row per entry for your appliances: Appliance, Own watts, How many or Hours / day.
  2. Choose currency: $, £, €, ৳ and more.
  3. Enter electricity price (per kWh).
  4. Enter days used per month.
  5. Enter fixed monthly charge (optional) - optional.
  6. Enter peak sun hours per day.
  7. Enter solar system cost (optional) - optional.
  8. Enter solar size in kW (optional) - optional.
  9. Enter yearly electricity price rise (% / year).
  10. Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.

About the Electricity Cost & Solar Payback

Find out what your appliances cost to run and whether solar would pay off. Pick each appliance (or enter its watts), how many you have and the hours it runs each day. The calculator adds up the monthly kWh and bill, shows which appliance costs the most, then sizes a solar system to cover your usage and works out the monthly saving, the payback period and the 25-year net gain from the system cost and your electricity price.

Also known as: electricity bill calculator, appliance power consumption calculator, AC electricity cost calculator, solar payback calculator, kWh cost calculator.

Formula and cut-offs

Energy (kWh per month) = watts x quantity x hours per day x days / 1,000. Cost = kWh x price per kWh + fixed charge. Solar size (kW) = monthly kWh / (peak sun hours x 0.8 x days). Yearly saving = solar kWh used x price, with the price rising each year and output falling 0.5% a year. Payback = the year cumulative savings equal the system cost.

Frequently asked questions

How do I calculate the electricity cost of an appliance?

Multiply its power in watts by the hours used per day and divide by 1,000 to get kWh per day. Multiply by the days in the month and by your price per kWh. A 1,300 W AC running 8 hours a day for 30 days uses 312 kWh.

Why does my air conditioner or fridge use less than its label says?

Compressor appliances switch on and off to hold the temperature, so they draw full power only part of the time. Enter the hours the compressor actually runs, or about half the hours it is switched on.

How long does solar take to pay back?

Residential solar often pays back in about 5 to 10 years where electricity prices are high and the system is sized to daytime use. It depends on the installed cost, your tariff, sunshine, net metering rules and shading.

How many solar panels do I need?

Divide your monthly kWh by what one kW of panels produces in a month (peak sun hours x 0.8 x 30). One kW needs roughly 2 to 3 panels. This tool gives the kW size; ask an installer to confirm roof space and layout.

Sources and references

Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.

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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.