About this calculator
Not sure how many units you use? Switch to appliances: enter each appliance’s wattage and daily hours to estimate monthly units and cost.
How to use it
- Enter the units from your bill, or your appliances.
- Enter your slab rates, fixed charge and duty.
- Read the estimated bill and the slab breakdown.
The formula
Units = watts × hours × days ÷ 1,000; bill = Σ (units in slab × rate) + fixed charge + duty
- 1 unit
- 1 kWh: 1,000 W for 1 hour
Worked example
350 units with slabs ₹3, ₹4.50, ₹6 and ₹7.50
- 100 × ₹3 + 100 × ₹4.50 + 150 × ₹6 = ₹1,650.
- Add ₹100 fixed and 5% duty: about ₹1,838.
What the result means
Crossing into a higher slab only raises the rate for the extra units, not for all units, unless your DISCOM uses telescopic-free billing.
A 1.5-ton AC running 6 hours a day uses about 270 units a month.
Assumptions
- Rates are entered by you.
- A fridge’s compressor runs only part of the day, so about 10 hours is used.
Limitations
- Subsidies, rebates and minimum charges vary by state and are not modelled.
Frequently asked questions
What is 1 unit of electricity?
1 kilowatt-hour: a 1,000 W appliance running for one hour.
How many units does an AC use?
A 1.5-ton AC uses roughly 1 to 1.5 units an hour, depending on its star rating and settings.
Where do I find my slab rates?
On your bill or on your DISCOM or state electricity regulatory commission website.
Last reviewed on 6 October 2026. Found a mistake? Tell us.