Appliance Energy Cost Calculator
Enter wattage, hours, duty cycle and rate to get daily, monthly and yearly energy, cost and CO2.
Step-by-step
- Enter valid values to begin.
Power is treated as electrical input per unit; for a motor rated in mechanical HP the input is higher by 1 / efficiency, so enter nameplate input watts where you can. Duty cycle is the average fraction of operating hours the load is actually drawing rated power (a compressor or thermostat cycles). Standby watts are drawn for the remaining 24 − operating hours on each day of use. A year is 12 months of the entered days; the week and long-term rows spread the monthly use over 365/12 days per month. The default 0.4 kg CO₂/kWh is an approximate mixed-grid figure and varies widely by country and hour, so replace it with your local value.
Appliance Running Cost: Turning Nameplate Watts into Money
Core Engineering Principles
A nameplate gives you the maximum the appliance can draw, and almost nothing runs at that figure all day. A refrigerator compressor cycles, a kettle element stops at the boil, a heat-pump compressor modulates. So we multiply rated power by hours and then by a duty cycle, the fraction of the on-time the load actually pulls rated power. The best way to find that fraction is a plug-in energy meter left on for a week. Check it reads watts, not volt-amperes; on a motor or switch-mode supply the two differ by the power factor.
Standby is the other trap. A five watt adapter sounds like nothing, yet 5 W over 8,760 hours is 43.8 kWh a year, per device, forever. For small loads such as printers, chargers and set-top boxes, idle consumption can rival the working energy, so we count standby for the hours the appliance is not working. The cumulative table shows lifetime cost, which is why a cheap, inefficient appliance usually loses to a dearer one within a few years.
Cost = kWh × rate • CO₂ (kg) = kWh × EFgrid
NEC & Standard References
IEC 62301 defines how to measure standby power in household appliances. IEEE Std 1459 defines active, reactive and apparent power for sinusoidal and non-sinusoidal conditions, which is why a watt reading and a VA reading differ. ENERGY STAR and EU Ecodesign rules set standby limits by product category. For emissions, GHG Protocol Scope 2 guidance explains grid factors, which vary by country and year; use your utility’s figure and confirm the edition.1. Active = 2 × 750 × 8 × 0.60 / 1000 = 7.20 kWh/day.
2. Standby = 2 × 5 × 16 / 1000 = 0.16 kWh/day, so the total is 7.36 kWh/day and costs 1.10.
3. Monthly = 7.36 × 30 = 220.8 kWh, which is 33.12.
4. Yearly = 220.8 × 12 = 2,649.6 kWh, which is 397.44; over five years it is 1,987.20 at a flat rate.
5. CO₂ = 2,649.6 × 0.4 = 1,060 kg per year.
- Don’t use the nameplate as the average. It overstates a cycling load and understates a load with a large inrush or poor power factor.
- Start-up surges are real. A compressor draws several times its running current briefly; size the circuit for it.
- Standby adds up across a site. Fifty chargers and monitors at 3 W each is 150 W running all night.
- HP is not input power. A 1 HP motor delivers 745.7 W on the shaft and draws more from the line by 1 / efficiency.
- Rates change. A flat-rate five-year total ignores escalation and time-of-use pricing.