Available calculators
A careful approach to savings estimates
Prices, tariffs, property conditions and personal habits vary by place. These tools show their assumptions in the inputs, so you can replace every cost with your own figure.
How payback is worked out
Every tool here compares an upfront cost with a yearly saving. Simple payback = upfront cost / annual saving. Replacing a 60 W incandescent bulb with a 9 W LED that runs 3 hours a day saves 51 W × 3 h × 365 = 55.8 kWh a year, or $8.38 at $0.15 per kWh; a $3 bulb pays for itself in under five months.
| Upfront cost | Annual saving | Simple payback |
|---|---|---|
| $3 | $8.38 | 0.4 years |
| $2,500 | $400 | 6.3 years |
| $9,000 | $900 | 10 years |
Simple payback ignores energy-price changes, maintenance, financing and the value of money over time. Use your own local prices: the result is only as good as the price and usage figures you enter.