Electricity Cost Calculator,
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Field guide

How to calculate appliance running costs and cut your electricity bill.

Understanding wattage and kilowatt-hours

Every electrical appliance has a power rating measured in watts (W). This number tells you how much electrical energy the appliance consumes at any given moment. A 100 W light bulb uses 100 watts continuously while it is on; a 3,500 W central air conditioner uses 3,500 watts while running.

Your electricity bill is measured in kilowatt-hours (kWh), not watts. A kilowatt-hour is the energy consumed by a 1,000-watt appliance running for one hour. To convert from watts to kilowatt-hours:

So a 1,000 W microwave running for 30 minutes (0.5 hours) uses 1,000 × 0.5 ÷ 1,000 = 0.5 kWh. At $0.16 per kWh, that costs 8 cents — which quickly adds up if you run the microwave multiple times per day, every day.

The real cost formula

The rate varies significantly by location and utility provider. In the United States, the residential average is around $0.13–0.17/kWh as of 2024, though Hawaii pays over $0.40/kWh and some states are below $0.10. In the UK, the Ofgem price cap places typical rates around £0.24/kWh (≈ $0.30). In the EU, rates average about €0.25/kWh but range from €0.12 (Hungary) to €0.42 (Denmark).

Always check your actual electricity bill for your precise rate. The unit price, standing charges, and any applicable taxes all affect the final cost.

Which appliances cost the most?

The total cost depends on both wattage and daily usage hours — a high-wattage appliance used briefly may cost less than a low-wattage appliance running all day. Here is a breakdown of typical annual costs at $0.16/kWh:

• Electric water heater (4,500 W, 3 hrs/day): ≈ $790/year — one of the largest contributors to electricity bills in most homes.
• Central AC (3,500 W, 8 hrs/day in summer): ≈ $500/year (seasonally used — less in cooler climates).
• Clothes dryer (5,000 W, 1 hr/day): ≈ $290/year.
• Refrigerator (150 W, 24 hrs/day): ≈ $210/year — low wattage but always on, making it a significant cumulative cost.
• Gaming PC (500 W, 4 hrs/day): ≈ $117/year.
• LED TV, 55" (80 W, 5 hrs/day): ≈ $23/year.
• LED bulb (10 W, 5 hrs/day): ≈ $3/year — dramatically cheaper than the 60 W incandescent it replaces ($18/year).

Effective ways to reduce appliance running costs

• Switch to LED lighting: A single LED bulb uses 80–90% less energy than an equivalent incandescent. In a home with 30 bulbs, this can save $150–$200 per year with no change in behaviour.
• Use smart plugs and timers: Devices like gaming consoles, cable boxes, and monitors draw power in standby. Smart plugs set to cut power during off-hours eliminate this hidden "phantom load," which can amount to 5–10% of a household electricity bill.
• Upgrade to Energy Star appliances: Refrigerators, washing machines, and dishwashers certified by Energy Star use 15–50% less energy than non-certified equivalents. The upfront premium is typically recovered in 3–5 years through lower bills.
• Manage heating and cooling: HVAC systems account for 40–50% of residential electricity use in many climates. A programmable thermostat that reduces heating/cooling during unoccupied hours can cut HVAC costs by 10–15%.
• Wash with cold water: About 90% of the energy used by a washing machine goes to heating the water. Cold-water washing saves most of this energy with no reduction in cleaning performance for most loads.
• Time-of-use rates: Many utility companies offer time-of-use (TOU) pricing with lower rates during off-peak hours (typically overnight). Running dishwashers, washing machines, and EV chargers during off-peak periods can reduce costs by 10–30% on these appliances.

Standby power and phantom loads

Many appliances continue to draw power even when switched off. This standby or "vampire" power typically ranges from 0.5 W to 10 W per device. Over a year, a device drawing 5 W continuously costs about $7/year at $0.16/kWh. A home with 20 such devices adds $140/year in costs that produce no useful function. Using power strips with on/off switches or smart plugs on devices not in use eliminates this waste entirely.

Disclaimer

Costs shown are estimates based on the wattage, daily hours, and electricity rate you enter. Actual wattage varies between specific models and operating conditions. The 30.4-day month and 365-day year are used for consistency. Running cost estimates do not include any standing charges, taxes, or network fees that may appear on your actual electricity bill.