Understanding your electricity use: watts and kilowatt-hours

The formula

kWh = power in watts × hours of use ÷ 1000

A kilowatt-hour is 1,000 watts used for one hour.

Worked examples (per month, 30 days)

• A 2,000 W electric heater used 4 hours a day: 2,000 × 4 × 30 ÷ 1000 = 240 kWh.
• A 60 W old bulb used 5 hours a day: 9 kWh.
• A 10 W LED bulb giving similar light: 1.5 kWh.

Appliances that heat or cool — heaters, water heaters, air conditioners, irons, ovens — use far more than lights and electronics.

How bills are priced

Household electricity in Iran is priced in tiers: the price per kWh rises as monthly use goes up, and use at peak hours can cost more. Keeping monthly use in the lower tiers can save noticeably more than the kWh saved alone.

Simple savings

• Replace old bulbs with LEDs.
• Set air conditioners a little warmer and heaters a little cooler.
• Run washing machines and dishwashers full, and outside peak hours.
• Switch off appliances at the wall instead of leaving them on standby.

Tools for this

• Utility bill estimator