Electricity bill calculator
Free, no sign-up · Facts checked 18 Oct 2026
Your electricity bill from your own slabs, one rate or the Tamil Nadu tariff.
1Your slabs · 450 units in a month
Your bill for the month₹2,350- Units
- 450 units
- Average a unit
- ₹5.22
Work it out
Your bill for the month
₹2,350
₹5.22 a unit on average
450 units for the month comes to ₹2,350.
- Units
- 450 units
- Average a unit
- ₹5.22
- Your next unit costs
- ₹7
Your next unit costs ₹7.
Your bill as units go up
Each slab costs more per unit than the one before.
What it is made of
Point at a part to see it on its own.
From your numbers
Worked out from what you entered. Try one.
- Your next unit costs ₹7, against an average of ₹5.22 a unit. Cutting use saves at the top rate first.
- A 1.5-ton AC for 6 hours a day uses about 234 units in 1 month: it would add ₹1,638 to this bill.
Milestones
How your bill is worked out
Always open. Point at a row to find it on the chart.
| Units | In this slab | Rate | Cost |
|---|---|---|---|
| 1–100 | 100 | ₹3 | ₹300 |
| 101–300 | 200 | ₹5 | ₹1,000 |
| Above 300 | 150 | ₹7 | ₹1,050 |
| Total | 450 | ₹2,350 |
Full breakdown
- Units
- 450 units
- Average a unit
- ₹5.22
- Your next unit costs
- ₹7
Guide
Your own slabs, like a spreadsheet
Most electricity boards bill on slabs: the first units are cheap, and each higher band costs more per unit. Your bill or your board’s tariff page lists them. Pick My slabs and type them into the table: each row is up to a number of units at a rate, and the last row is everything above. The tool starts with an example (₹3 up to 100 units, ₹5 up to 300, ₹7 above); change the rows to yours, add or delete rows, and the bill updates as you type. If you pay one price for every unit, pick One rate.
Why did my Tamil Nadu bill jump after 500 units?
In Tamil Nadu, homes are billed every two months on a telescopic tariff: the first units are free, the next ones cheap, and only the units in each higher slab cost more. Since 10 May 2026 there is one big step in the middle. If you use 500 units or fewer in two months, the first 200 units are free. Go even one unit over 500 and only the first 100 units are free, and the units above 500 start at ₹8.40.
| Units in 2 months | Up to 500 units used | More than 500 units used |
|---|---|---|
| 1–100 | Free | Free |
| 101–200 | Free | ₹4.70 a unit |
| 201–400 | ₹4.70 a unit | ₹4.70 a unit |
| 401–500 | ₹6.30 a unit | ₹6.30 a unit |
| 501–600 | – | ₹8.40 a unit |
| 601–800 | – | ₹9.45 a unit |
| 801–1,000 | – | ₹10.50 a unit |
| Above 1,000 | – | ₹11.55 a unit |
So 500 units cost ₹1,570, but 501 units cost ₹2,048.40: that single unit adds about ₹478, because 100 units stop being free. This calculator shows the jump on its chart and tells you how close you are.
Lakshmi’s bill in Kallakurichi
Lakshmi’s family in Kallakurichi used 520 units in May and June, when the fans and the new AC ran every night.
- On 520 units only 100 are free: 300 units at ₹4.70 (₹1,410), 100 at ₹6.30 (₹630) and 20 at ₹8.40 (₹168). The bill is ₹2,208.
- Had they used 500 units, it would have been ₹1,570, ₹638 less for just 20 units.
- Their next unit costs ₹8.40, while their average is only ₹4.25 a unit. Saving at the top rate pays the most.
Switching the AC off an hour earlier each night (about 78 units in two months) would have brought them under 500.
How to use this tool
- Pick My slabs (type your board’s slabs into the table), One rate or Tamil Nadu.
- Type the units on your bill, or turn on Meter readings and type the last and current readings.
- Read the bill, the average and what your next unit costs. The chart shows where you sit on the curve.
- Turn on Add an appliance to see what an AC, geyser or pump adds, Last bill to compare, or Fixed charge and tax to add charges from your bill.
Reading your meter
The units on your bill are the current reading minus the previous reading. Read only the white digits on a mechanical meter, or the kWh value on a digital meter (it cycles through screens; wait for the one marked kWh). If the new reading is lower than the old one, the meter was probably changed: use the units printed on the bill.
What uses the most units
Power (kW) × hours = units. A 1.5-ton AC at about 1.3 kW for 6 hours a day uses about 470 units in two months. A 2 kW geyser for half an hour a day uses about 60. A ceiling fan for 12 hours uses about 54. Big items that run for hours, such as ACs, pumps and geysers, decide which side of 500 you land on.
Common mistakes
- Thinking the whole bill jumps to a higher rate. Only the units in each slab cost that slab’s rate; what changes at 500 is the free units.
- Comparing the average cost per unit with the next unit’s cost. Savings come off the top slab.
- Forgetting that the bill is for two months in Tamil Nadu.
Sources
Facts checked 18 Oct 2026TNERCOrder No. 4 of 2026: Provisional Tariff Subsidy Order for FY 2026-27 · Tamil Nadu Electricity Regulatory Commission2026
Domestic (LT I-A) rates consumers pay after the subsidy: ₹4.70, ₹6.30, ₹8.40, ₹9.45, ₹10.50 and ₹11.55 a unit by bimonthly slab, 100 units free. 27 Apr 2026
TNERCOrder No. 5 of 2026: Additional Tariff Subsidy Order for FY 2026-27 · Tamil Nadu Electricity Regulatory Commission2026
From 10 May 2026 (G.O.(Ms) No. 50), 200 units free every two months up to 500 units; above 500 the old structure with 100 free units stays. 26 May 2026
TNERCTariff Orders · Tamil Nadu Electricity Regulatory Commission2026
Where new tariff and subsidy orders appear; check here for later changes. checked 18 Oct 2026
Questions
How is the TNEB bill calculated?
Units are billed every two months in slabs. Up to 500 units, the first 200 are free, then ₹4.70 and ₹6.30 a unit. Above 500, only 100 are free and higher slabs start at ₹8.40.
Why is my bill much higher after 500 units?
Crossing 500 units takes away 100 free units and starts the ₹8.40 slab. 501 units cost about ₹478 more than 500 units.
How much does 1 unit of electricity cost in Tamil Nadu?
It depends on your slab: free, ₹4.70, ₹6.30, ₹8.40, ₹9.45, ₹10.50 or ₹11.55. The tool shows what your next unit costs.
How many units does a 1.5-ton AC use?
About 1.3 units an hour while running, so 6 hours a day is roughly 470 units over a two-month bill. Inverter and star-rated models use less.
Can I use it for other states or countries?
Yes. Choose My slabs and type the slabs from your bill into the table, or One rate for a single price per unit.
Does it include fixed charges?
Only if you add them. Turn on Fixed charge and tax and type what your bill shows.