Power & Energy Calculator
Calculate how much energy an appliance uses, what it costs to run, and how much CO₂ it produces. Useful for comparing appliances and understanding your electricity bill.
Electrical Energy Guide
Understanding kWh
A kilowatt-hour (kWh) is the standard unit of electrical energy on your bill. One kWh = 1,000 watts running for 1 hour (or 100 watts for 10 hours, etc.). Energy = Power (kW) × Time (hours). A 2kW kettle used for 5 minutes uses 0.17 kWh. At 24.5p/kWh, that is 4p per boil. UK electricity price as of October 2024 is approximately 24.5p/kWh (Ofgem price cap). Annual household electricity usage averages 2,700–4,100 kWh depending on household size.
Most Expensive Appliances
Annual running costs at 24.5p/kWh and typical usage: electric storage heater (1kW × 8h = £714/year), immersion heater (3kW × 2h/day = £536), tumble dryer (2.5kW × 2h × 3 days/week = £191), electric oven (2kW × 1h/day = £179), dishwasher (1.2kW × 1h/day = £107), washing machine (1kW × 1h/day = £89), fridge-freezer (300W constant = £64), TV (80W × 4h/day = £28), LED lights (10W × 5h/day per bulb = £4.50). Replacing a 3-hour-per-day incandescent bulb (60W) with LED (8W) saves approximately £12/year
CO₂ and Carbon Intensity
The UK electricity grid's carbon intensity averages approximately 225g CO₂/kWh (2024), down from over 500g in 2000 as coal is replaced by renewables. At 225g/kWh, a 2kW tumble dryer used for 2 hours emits approximately 900g CO₂ per use. Annual household electricity use of 3,500 kWh produces approximately 790kg CO₂. Carbon intensity varies significantly by time of day — typically lower when wind generation is high (often at night or in stormy weather). Apps like Electricity Maps or the National G
Energy Efficiency Ratings
UK appliance energy labels use an A–G scale (A+++ to G for older products). An A-rated fridge uses approximately 30% less energy than a D-rated equivalent. The EU/UK energy label shows estimated annual kWh consumption — divide by 365 for daily consumption and multiply by your unit rate. Heat pump tumble dryers (A-rated) typically use 1.5–2kWh per cycle vs 5kWh for a vented dryer — a significant running cost difference for heavy users. Induction hobs are approximately 85% efficient vs 70% for gas
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