Watts, kilowatt-hours and your bill
Watts measure the rate of energy use; kilowatt-hours measure the total consumed. A 1,000 W appliance running for one hour uses exactly 1 kWh, which is the unit your utility bills you for.
The formula is watts ÷ 1000 × hours × price. Everything else on this page is that one line applied over different periods.
Where household electricity actually goes
Heating and cooling dominate — air conditioners, water heaters and space heaters draw 1,500 to 3,000 watts and often run for hours. Anything that heats or moves air is expensive.
Electronics on standby are a much smaller line than commonly assumed, typically 1–5 watts each. Worth eliminating, but not where the savings are. Run the numbers on your air conditioner first.
Tiered and time-of-use tariffs
Many utilities charge in slabs, so the price per unit rises once monthly consumption crosses a threshold. Under a tiered tariff, the marginal cost of extra usage is higher than the average rate on your bill — use the top-tier rate when working out what an additional appliance costs.
Time-of-use tariffs charge more during peak hours. Where those apply, shifting the dishwasher, washing machine or electric-vehicle charging to off-peak hours reduces the bill without reducing consumption at all.
Finding the biggest savings
Multiply wattage by hours, not wattage alone. A 2,000 W kettle used ten minutes a day costs less than a 60 W device left on continuously. High-wattage, long-duration appliances — heating, cooling, water heating — are where household savings actually live.
Replacing incandescent bulbs with LEDs cuts lighting energy by roughly 85%, but lighting is typically only 5–10% of a household bill. Worth doing, but it will not transform the total.
Frequently asked questions
Where do I find the wattage? +
On the rating plate, usually on the back or underside, or in the manual. If only amps and volts are listed, multiply them: 5 A at 230 V is 1,150 W.
How do I find my rate per kWh? +
It is on your electricity bill, usually as a per-unit charge. Dividing the total bill by units consumed gives an effective rate that includes fixed charges and taxes.
Does standby power matter? +
Less than commonly believed. Modern devices draw 0.5 to 2 watts on standby — real but small next to anything that heats or cools.