Appliance Running Cost Calculator
Enter the wattage and how long it runs. For anything with a compressor or thermostat, set the duty cycle — it is the difference between a useful answer and a wildly wrong one.
How this is calculated
The formula is simple. Getting the inputs right is where people go wrong.
kWh = (watts ÷ 1000) × hours per day × days per year × duty cycle
Cost = kWh × your rate
Duty cycle: the input everyone gets wrong
Plug a 150W refrigerator into a naive calculator with "24 hours a day" and you get 1,314 kWh and $229 a year. The real figure is closer to $80.
Fridges do not draw 150W continuously. The compressor cycles on and off to hold temperature, typically running about 35% of the time. That single correction changes the answer by a factor of three.
Rough duty cycles worth using:
| Appliance | Duty cycle | Why |
|---|---|---|
| Refrigerator | 30–40% | Compressor cycles on thermostat |
| Chest freezer | 35–45% | Colder target, runs more |
| Air conditioner | 50–70% | Depends heavily on outside temperature |
| Space heater (thermostat) | 40–70% | Cycles once the room is warm |
| Space heater (no thermostat) | 100% | Full draw whenever switched on |
| Kettle, microwave, dryer | 100% | Full power for their whole cycle |
| TV, computer, lighting | 100% | Steady draw while on |
What actually costs money in a typical home
People worry about phone chargers and ignore the water heater. Roughly, for an average US home:
| Category | Share of bill | Typical annual cost |
|---|---|---|
| Heating and cooling | ~45% | $700–900 |
| Water heating | ~14% | $220–280 |
| Refrigeration | ~7% | $80–120 |
| Lighting | ~5% | $60–100 |
| Laundry and dishwashing | ~5% | $60–100 |
| Electronics and standby | ~10% | $120–200 |
The practical takeaway: switching every bulb to LED saves perhaps $50 a year. Adjusting your thermostat by 2°F saves roughly the same for far less effort. If you want to cut a bill, start with heating and cooling — everything else is rounding error by comparison.
Standby power
Individually trivial, collectively not. A device drawing 3W continuously costs about $4.60 a year. A typical home has 20–40 such devices — call it $50–100 a year for things that are switched off. Worst offenders are set-top boxes, games consoles, older televisions, and anything with a warm power brick.
Assumptions
- US average residential electricity: $0.1745/kWh (EIA)
- Appliance presets use typical mid-range figures — always prefer your own rating plate
Common questions
Where do I find my appliance's wattage?
Check the rating plate — usually a sticker on the back, base or inside the door. It may show watts (W) directly, or volts and amps, in which case watts = volts x amps. The manual and the manufacturer's website normally list it too. If all else fails, a plug-in energy monitor costs about $20 and measures actual draw, which beats any estimate.
What is duty cycle and why does it matter so much?
Anything with a thermostat — fridge, freezer, air conditioner, electric heater — does not draw full power continuously. It cycles on and off to hold a temperature. A fridge plugged in 24 hours a day might only run its compressor 8 of those hours, a 35% duty cycle. Ignoring this overstates a fridge's cost by roughly three times, which is the most common error in appliance calculations.
Does standby power matter?
It adds up more than people expect. Devices drawing 1–5W continuously cost roughly $1.50–7.50 each per year, but a typical home has 20–40 of them — often $50–100 a year in total for devices doing nothing. Televisions, games consoles, set-top boxes and anything with an external power brick are the usual culprits.
Is it cheaper to run appliances at night?
Only if you are on a time-of-use tariff. On a flat rate, electricity costs the same at 3am as at 3pm. If you are on time-of-use, shifting dishwashers, laundry and EV charging to off-peak hours can cut those costs by half or more. Check your bill — it will say which type of plan you are on.