Electricity Cost Calculator
Enter an appliance's wattage, daily usage, and your electricity rate to see the exact running cost per hour, day, month, and year.
How It Works
Electricity is measured and billed in kilowatt-hours (kWh). One kWh is the energy used by a 1,000-watt device running for one hour.
Energy consumed per day:
kWh/day = (Watts × Hours per day) ÷ 1,000
Cost per day:
Cost/day = kWh/day × Rate ($/kWh)
Scaling up:
- Cost/hour = Cost/day ÷ Hours per day
- Cost/month = Cost/day × 30.4375 (average days per month)
- Cost/year = Cost/day × 365.25
CO₂ emissions:
CO₂ (kg/year) = kWh/year × 0.233
This uses the approximate global average grid emission factor of 0.233 kg CO₂ per kWh (IEA 2023). Your actual emissions depend on your local energy mix.
Worked example: A 2,000 W electric oven used 1 hour per day at $0.15/kWh:
kWh/day = 2,000 × 1 ÷ 1,000 = 2 kWh
Cost/day = 2 × $0.15 = $0.30
Cost/month = $0.30 × 30.4375 ≈ $9.13
Cost/year = $0.30 × 365.25 ≈ $109.58
CO₂/year = 2 × 365.25 × 0.233 ≈ 170.2 kg
Common appliance wattages (approximate):
LED bulb: 10 W, Fridge: 150 W, Washing machine: 500 W, Tumble dryer: 2,500 W, Dishwasher: 1,800 W, Electric oven: 2,000 W, Microwave: 1,000 W, 65" TV: 150 W, Desktop PC: 200 W, Laptop: 65 W.
Frequently Asked Questions
Where do I find the wattage of my appliance?
Check the rating label on the back or bottom of the appliance, or look in the user manual. It is often listed as "Input: X W" or "Max: X W". For variable-power devices like laptops, use the charger's rated wattage as a maximum estimate; actual consumption is typically 40–70 % of that figure under normal use.
How do I compare two appliances for running cost?
Run this calculator twice — once for each appliance — with the same usage hours and rate. Alternatively, look at the Energy Star rating or annual kWh figure on the appliance's yellow EnergyGuide label (in the US). A fridge rated at 400 kWh/year costs about $60/year at $0.15/kWh; one rated at 600 kWh/year costs $90/year.
What is phantom load (standby power)?
Many devices draw power even when "off" — TVs, game consoles, phone chargers, and smart devices can draw 1–15 W on standby. Multiplied across a household, this can add up to 10 % of your electricity bill. Use smart power strips or unplug devices when not in use to eliminate standby draw.
How do I find my electricity rate?
Look at your most recent electricity bill. The rate is usually listed as cents per kWh (e.g., 15¢/kWh = $0.15/kWh). In the US, average residential rates range from about $0.10 to $0.30/kWh depending on state. In the UK, the rate is around £0.24/kWh; in Australia, around $0.25–$0.35 AUD/kWh.
How much can solar panels save?
A home solar system offsets the electricity you would otherwise buy from the grid. If your solar panels produce all the power an appliance consumes, the running cost drops to near zero (aside from panel amortisation). Run this calculator with your current rate to see annual cost, then compare it to your solar system's estimated annual output.