How electricity units are calculated
One unit of electricity is one kilowatt-hour (kWh) — 1,000 watts used for one hour.
Units = Watts × Hours per day × Days ÷ 1,000
| Appliance | Power | Use per day | Units a month |
|---|---|---|---|
| Ceiling fan | 75 W | 10 hours | 22.5 |
| LED bulb | 9 W | 6 hours | 1.6 |
| Refrigerator | 150 W | ≈10 hours of compressor running | 45 |
| AC (1.5 ton) | 1,500 W | 8 hours | 360 |
| Geyser | 2,000 W | 1 hour | 60 |
| Television | 100 W | 4 hours | 12 |
An AC is by far the biggest load: one 1.5-ton AC running 8 hours a day uses about as much as 16 fans. Inverter and 5-star ACs use noticeably less.
How a slab-wise bill is calculated
Domestic tariffs in India are telescopic: each slab's rate applies only to the units inside that slab. With example slabs of ₹3.50 (first 100 units), ₹5 (101–200), ₹6.50 (201–400) and ₹7.50 (above 400), 250 units cost:
- 100 units × ₹3.50 = ₹350
- 100 units × ₹5.00 = ₹500
- 50 units × ₹6.50 = ₹325
- Energy charge = ₹1,175
Add the fixed charge (₹50 here) and electricity duty (5% here) to get about ₹1,286. Your bill may also show fuel surcharge (FPPCA), meter rent or subsidies — add or subtract them as listed.
Tariffs differ by state
Every state's electricity regulator sets its own slabs and rates, usually revised once a year, and many states give free or subsidised units to households below a limit. The slabs in this calculator are examples — open “Tariff slabs” and type in the rates printed on your bill or published on your DISCOM's website.
Ways to cut your bill
- Set the AC to 24–26 °C — each degree lower adds roughly 6% to its consumption.
- Replace old tube lights and CFLs with LEDs and old fans with BLDC fans (about 30 W instead of 75 W).
- Prefer 5-star rated appliances (BEE star label) when buying new.
- Switch geysers and pumps off when not needed; use a timer.
- Turn off appliances at the plug — standby power adds up.
- Consider rooftop solar — under PM Surya Ghar, central subsidy is available for homes.
Frequently asked questions
How do I calculate my electricity bill from units?
Multiply the units in each slab by that slab's rate, add them up, then add the fixed charge and electricity duty. Enter your units and your DISCOM's slabs in the calculator to do this automatically.
How many units does a 1.5 ton AC use?
About 1.5 units an hour at full load — roughly 360 units a month at 8 hours a day. Inverter and 5-star models use less, depending on the room and temperature setting.
What is 1 unit of electricity?
One kilowatt-hour (kWh): 1,000 watts used for an hour, or a 100 W device running for 10 hours.
Why doesn't my bill match exactly?
Bills can include fuel adjustment surcharge, meter rent, subsidies, arrears and rounding. Add these to the fixed charge field, and make sure the slabs match your latest tariff.
How many units does a fridge use in a month?
A typical double-door refrigerator uses about 30–60 units a month. Newer 5-star models are at the lower end.