Energy Usage Calculator
Work out how much energy your appliances use — up to three, with watts and hours per day — in kWh and in cost at your tariff.
Which appliance costs the most to run? It is watts times hours — and the answer is rarely the one you expect. This calculator shows each appliance's share.
Enter the watts and the hours; the kWh and the cost follow.
Your results
Enter your measurements and press Calculate.
Quantities are rounded up to whole tiles, planks, boxes or bags, after the wastage allowance. Cost appears only when you enter a price.
Formula
All lengths are converted to a single unit before the calculation: 1 ft = 0.3048 m, 1 in = 25.4 mm, 1 ft² = 0.09290304 m², 1 yd² = 9 ft². Material quantities are rounded up — you cannot buy part of a tile, plank or bag.
How to use this calculator
- Enter each appliance's watts and hours per day (up to 3).
- Enter the days and your tariff.
- Read each appliance's kWh, the total kWh and the total cost.
Worked example
| Appliance 1 | 100 W × 5 h × 30 days = 15 kWh |
|---|---|
| Appliance 2 | 1,500 W × 1 h × 30 days = 45 kWh |
| Appliance 3 | 60 W × 8 h × 30 days = 14.4 kWh |
| Total | 15 + 45 + 14.4 = 74.4 kWh |
| Cost at $0.15/kWh | 74.4 × $0.15 = $11.16 |
Check it by hand: every step above uses the formula in the box. If your numbers match the example inputs but the calculator gives a different answer, please report it via the contact page.
Frequently asked questions
How do I find an appliance's watts?
On its label or manual — or measure it with a plug-in energy meter. A TV is typically 50–150 W; a kettle 1,500–3,000 W; an LED light 5–15 W.
Why does the kettle cost more than the TV?
Because watts decide the cost, not hours: a 1,500 W kettle for 1 hour uses 1.5 kWh, while a 100 W TV for 5 hours uses 0.5 kWh. This calculator shows the split.
Can I use this for more than 3 appliances?
Three covers most checks. For a whole house, group appliances (e.g. 'all lighting', 'all kitchen') or run the calculator twice and add the totals.
Is this a quote?
No. It is an estimate from your own watts, hours and tariff — not a guaranteed bill.
Related calculators
Estimates only. Results are for planning. Measure twice, confirm box coverage and tile sizes on the packaging you buy, and follow the manufacturer's instructions. See the disclaimer.