Electricity Cost Calculator
Find what an appliance costs to run per hour, day, month and year. Advanced adds several appliances, standby, on-time, peak prices, CO₂ and payback on a new model.
On-time is the share of the running time it really draws power: fridges, freezers, AC and heaters switch on and off with the thermostat (often 30–60%).
Find it on your bill as the unit rate or energy charge.
About 0.45 kg is a rough world average. Grids with lots of hydro, nuclear, wind or solar are far lower; coal-heavy grids are higher. Your supplier or grid operator may publish your figure.
Uses the same hours, days and on-time as appliance 1. Energy labels often give the yearly kWh: divide by the hours it runs in a year to get average watts.
Costs by period and by appliance
| Period | kWh | Cost | With standing charge | CO₂ |
|---|
| Appliance | kWh a year | Cost a year | Share |
|---|
How your electricity cost is worked out
Cost = kW × hours × price per kWh.
- 1
Power in kW
100 W ÷ 1000= 0.1 kW
- 2
Energy a day
0.1 kW × 5 h= 0.5 kWh
- 3
Cost a day
0.5 kWh× $0.15= $0.075
- 4
Cost a year
$0.075 × 365= $27.38
Read more: the formula, a worked example, standby, on-time, peak prices and typical wattages
Electricity is sold by the kilowatt-hour (kWh): 1,000 watts running for one hour. Turn the appliance's watts into kilowatts, multiply by the hours it runs to get kWh, then multiply by your price per kWh.
The formula
kW = watts ÷ 1000 (or amps × volts × power factor ÷ 1000)
kWh a day = kW × hours on × on-time % × how many
+ standby watts ÷ 1000 × hours off
average day = (kWh on days used × days a week + standby on other days) ÷ 7
cost = kWh × price per kWh (+ tax)
cost a year = cost a day × 365; a month = a year ÷ 12
bill = cost + standing charge per day × days
payback = price of new model ÷ yearly saving
Worked example
A 100 W appliance used 5 hours a day at $0.15 per kWh: 100 W ÷ 1000 = 0.1 kW. 0.1 kW × 5 hours = 0.5 kWh a day. 0.5 × $0.15 = $0.075 a day. Over a year that is 0.5 × 365 = 182.5 kWh and $0.075 × 365 = $27.375, about $27.38, or $2.28 a month. Each hour it is on costs 0.1 × $0.15 = $0.015.
Standby, on-time and days a week
A fridge-freezer rated 150 W doesn't draw 150 W all day: the compressor runs only when the thermostat calls for it, perhaps 35% of the time. 0.15 kW × 24 h × 35% = 1.26 kWh a day, or 459.9 kWh a year. A TV used 5 hours a day on 5 days a week, with 0.5 W standby the rest of the time, uses 5 × (0.5 + 0.0005 × 19) + 2 × 0.0005 × 24 = 2.5715 kWh a week, an average of 0.367 kWh a day.
Peak and off-peak prices
With a peak price of 0.20 and an off-peak price of 0.08, using 30% of your power off-peak gives a blended price of 0.20 × 70% + 0.08 × 30% = 0.164 per kWh. Moving the dishwasher, washing machine or car charging to off-peak hours raises that share and lowers the blend.
Old vs new model
Swapping a 60 W filament bulb used 5 hours a day for a 9 W LED at $0.15 per kWh cuts the yearly use from 109.5 kWh ($16.43) to 16.43 kWh ($2.46), a saving of $13.96 a year. An LED costing $3 pays for itself in about 0.21 years, roughly 11 weeks.
Typical power of common appliances
| Appliance | Typical power | Typical use |
|---|---|---|
| LED bulb | 9 W | 5 h a day |
| Old filament bulb | 60 W | 5 h a day |
| TV (LED, 50 inch) | 100 W | 5 h a day |
| Laptop | 50 W | 6 h a day |
| Desktop computer | 200 W | 4 h a day |
| Games console | 150 W | 2 h a day |
| Wi-Fi router | 10 W | 24 h a day |
| Phone charger | 5 W | 2 h a day |
| Fridge-freezer | 150 W | 24 h a day, on 35% |
| Chest freezer | 100 W | 24 h a day, on 40% |
| Air conditioner (split, 1.5 ton) | 1.5 kW | 8 h a day, on 60% |
| Ceiling fan | 75 W | 8 h a day |
| Desk or stand fan | 50 W | 6 h a day |
| Electric space heater | 2 kW | 3 h a day, on 70% |
| Dehumidifier | 300 W | 8 h a day, on 70% |
| Electric kettle | 2 kW | 15 min a day |
| Microwave | 1 kW | 15 min a day |
| Electric oven | 2.4 kW | 1 h a day, 4 days a week, on 60% |
| Induction hob (one zone) | 2 kW | 1 h a day, on 60% |
| Toaster | 900 W | 6 min a day |
| Washing machine | 800 W | 1 h a day, 4 days a week |
| Tumble dryer | 2.5 kW | 1 h a day, 3 days a week, on 80% |
| Dishwasher | 1.2 kW | 1.5 h a day, 5 days a week, on 70% |
| Clothes iron | 1.2 kW | 20 min a day, 3 days a week, on 60% |
| Hair dryer | 1.5 kW | 10 min a day |
| Vacuum cleaner | 1 kW | 20 min a day, 2 days a week |
| Water heater (geyser) | 2 kW | 2 h a day, on 70% |
| Electric shower | 9 kW | 10 min a day |
| Water pump | 750 W | 1 h a day |
| EV home charger (7 kW) | 7 kW | 2 h a day, 3 days a week |
| Aquarium (heater + filter) | 50 W | 24 h a day, on 60% |
| Treadmill | 600 W | 30 min a day, 3 days a week |
These are rough typical figures, not measurements. The rating plate on the appliance, its energy label or a plug-in power meter gives a truer number. A rating plate shows the most it can draw, so the average is often lower.
Ways to cut the cost
- Heating and cooling (heaters, AC, water heaters, tumble dryers) use far more than electronics. A degree or two on the thermostat often saves more than switching off small gadgets.
- Switch off at the wall: standby of a few watts, running 8,000 hours a year, adds up across many devices.
- Use off-peak hours if your plan has them, and run washing machines and dishwashers full.
- Check the yearly kWh on the energy label before you buy. The cheaper model can cost more over ten years.
Prices per kWh, standing charges and taxes differ by country, supplier and plan, and many plans charge more per kWh as you use more (tiers or slabs). Enter your own figures from your bill. Any price filled in at first is only an example. CO₂ factors vary widely by country and by year.
Common questions
How do I calculate the cost of running an appliance?
Divide the watts by 1,000 to get kW, multiply by the hours it runs to get kWh, then multiply by your price per kWh. A 100 W appliance used 5 hours a day uses 0.5 kWh, which costs 0.075 a day at 0.15 per kWh, or about 27.38 a year.
What is a kWh?
A kilowatt-hour is 1,000 watts used for one hour, and it's the unit your electricity price is charged in. A 100 W appliance takes 10 hours to use 1 kWh, while a 2 kW heater uses 1 kWh in half an hour.
How much electricity does a fridge use?
A fridge doesn't draw its full power all day, because the compressor runs only when the thermostat calls for it. A 150 W fridge-freezer running perhaps 35% of the time uses about 1.26 kWh a day, or 459.9 kWh a year. Use the on-time setting for fridges and AC.
How much does standby power cost?
Standby is usually only a few watts, but it runs for most hours of the year. A few watts running 8,000 hours a year adds up across many devices. Add an appliance's standby watts to include it, or switch off at the wall.
How do peak and off-peak prices change the cost?
Your average price is a blend of the two. With 0.20 peak, 0.08 off-peak and 30% of your use off-peak, the blend is 0.20 × 70% + 0.08 × 30% = 0.164 per kWh. Moving the dishwasher, washing machine or car charging to off-peak hours lowers it.
Is it worth switching to LED bulbs?
Usually. A 60 W bulb used 5 hours a day at 0.15 per kWh costs 16.43 a year to run, while a 9 W LED costs 2.46, a saving of 13.96 a year. An LED costing 3 pays for itself in about 0.21 years, roughly 11 weeks.
Related calculators
Made by Zulu Calculator, part of AlphaZulu LLC. Formulas are shown in full and rule figures are checked against official sources; see how we build calculators.