Three tenants each used 120 units. You read all three sub-meters, added them up, and got 360 units. The DISCOM bill for the main meter says 360 units too. The readings agree and the money still doesn't: bill the tenants individually and you collect Rs 1,770 against a bill of Rs 2,590.
Nobody tampered with anything. The Rs 820 hole comes from splitting a slab tariff with arithmetic that slabs don't support. Below is where the money goes, and the one splitting method that always closes to zero.
Table of contents
- The gap in numbers
- Why slabs don't split
- Splitting by one derived rate
- Unequal usage
- Common load
- Energy charge vs fixed charges
- Agreeing the method up front
- FAQ
- Sources
The gap in numbers
Every figure below uses one illustrative three-block tariff: Rs 4.50 for the first 100 units, Rs 7.00 for the next 100, Rs 9.00 after that. Your state commission publishes the real blocks and revises them, so read the slab table printed on your own bill before you settle anything. The structure is the same almost everywhere in India, even where the rates differ.
| Consumption | How it is charged | Total | Effective rate |
|---|---|---|---|
| 120 units | 100 x 4.50 + 20 x 7.00 | Rs 590 | Rs 4.92 |
| 360 units | 100 x 4.50 + 100 x 7.00 + 160 x 9.00 | Rs 2,590 | Rs 7.19 |
One tenant at 120 units pays Rs 4.92 per unit. The building at 360 units pays Rs 7.19 per unit for the same electricity. Multiply the single-tenant bill by three and you get Rs 1,770, which is 46% short of what the utility charged.
Why slabs don't split
The slab discount attaches to the connection, not to the person. Your building has one connection, so it gets one set of cheap first-100 units, and the tenants have used it up collectively by unit 100.
Bill each tenant alone and you hand out that cheap block three times. Three lots of 100 units at Rs 4.50 is 300 discounted units the utility never granted, because on a single meter only the first 100 units of the whole building are priced at Rs 4.50. Units 200 through 360 sit in the Rs 9.00 block, and no individual reading of 120 ever gets there.
The gap is built into a progressive tariff, and rounding has nothing to do with it. It grows with consumption: the deeper the main meter reaches into the expensive block, the wider the hole in your collection.
Splitting by one derived rate
Skip the slab table for tenants. Derive one rate from the bill you received:
flat rate = total energy charge on main bill / total units on main meter
= 2590 / 360
= Rs 7.1944 per unitThen charge every tenant that rate:
| Tenant | Units | Amount |
|---|---|---|
| A | 120 | Rs 863.33 |
| B | 120 | Rs 863.33 |
| C | 120 | Rs 863.33 |
| Total | 360 | Rs 2,590.00 |
The collection closes to the paisa, because you divided the real bill instead of rebuilding an imaginary one. Each tenant pays Rs 273 more than a naive slab calculation would give, which is their share of the expensive block their own usage helped reach.
Don't round the derived rate to two decimals before multiplying. Rs 7.19 across 360 units loses about Rs 1.60 against the real bill, and someone has to eat it. Keep four decimals, or divide the money instead of the rate.
Once you have the rate, the Indian Electricity Calculator turns each tenant's two meter readings into a payable amount every month. Feed it the derived rate, not a slab rate off the bill.
Unequal usage
Equal usage is the easy case. A wrong split looks defensible when consumption differs, and that is where this method earns its keep.
Same 360 units on the main meter, distributed as 60, 120 and 180:
| Units | Own-slab bill | Proportional share |
|---|---|---|
| 60 | Rs 270 | Rs 431.67 |
| 120 | Rs 590 | Rs 863.33 |
| 180 | Rs 1,010 | Rs 1,295.00 |
| 360 | Rs 1,870 | Rs 2,590.00 |
Own-slab billing leaves Rs 720 uncollected here. The proportional method closes exactly and keeps the ordering: the tenant who used three times as much pays three times as much. That heavy user carries a bigger share of a rate their consumption largely caused, which is about as fair as a single-connection tariff allows.
Common load
Corridor lights, the water pump, a lift and the motor for an overhead tank appear on no tenant's sub-meter, and all of them appear on the main meter.
Add 40 units of common load to the same building and the main meter reads 400 units, billing Rs 2,950. The tenants recorded 360 between them. Those 40 unattributed units land at the top of the tariff, in the Rs 9.00 block, so they cost Rs 360 rather than the Rs 288 an average-rate calculation would give.
Settle common load as its own line instead of inflating the per-unit rate. Split it equally per flat, or by floor area if the flats differ a lot in size. Rs 360 over three flats is Rs 120 each. Sub-meters also miss line losses in the cabling between the main board and each unit, a real residue that is usually small.
If electricity is one of several shared heads, the Shared Expense Split Calculator handles the whole set in one pass instead of one spreadsheet per bill.
Energy charge vs fixed charges
Derive the rate from the energy charge line on the bill, not the amount payable. A DISCOM bill also carries items unrelated to consumption.
Fixed or demand charges are billed against your sanctioned load in kW, so a locked flat that used zero units still gets one. Meter rent is a flat monthly amount where the utility owns the meter. Electricity duty and state cesses are applied on top of the tariff. The fuel and power purchase adjustment surcharge moves month to month with what the utility paid for power.
Divide the total payable by units and your rate absorbs all of that, so tenants end up paying a fixed charge that belongs to the connection. Pull the energy charge line out first, derive the rate from it, then share the fixed heads separately. Equal shares per flat are the usual answer.
Check subsidy credits too. They can make the net bill much lower than the gross, and passing on the gross while pocketing the credit invites a dispute.
Agreeing the method up front
The arithmetic isn't what makes these arguments ugly. The timing is. A method agreed before anyone has seen a bill reads as fair. The same method proposed after a Rs 2,590 bill arrives reads as an attempt to shift Rs 820.
Put four lines in the rental agreement, or in a WhatsApp message both parties keep:
- The per-unit rate is derived monthly by dividing the main meter's energy charge by its total units.
- Common-area load is the difference between the main meter and the sum of sub-meters, split equally per flat.
- Fixed charges, meter rent and duty are split equally per flat.
- Readings are taken on the same date each month, with photos.
The last line prevents more disputes than the rest combined. A reading taken four days late in an air-conditioned month moves real money, and a photo of the display settles in seconds what memory argues about for a week.
For a tenancy that ends mid-cycle, the Move-In / Move-Out Meter Settlement tool handles the part-period case, where the next official bill covers two different occupants.
FAQ
Why is the main meter bill higher than the sum of the sub-meters?
A slab tariff charges per connection. The cheap first block belongs to the building once, but billing each tenant separately hands it out once per tenant. At 120 units each, three tenants total Rs 1,770 while the 360-unit main bill is Rs 2,590.
What is the correct per-unit rate to charge a tenant?
The main bill's energy charge divided by the main meter's total units. On a Rs 2,590 bill for 360 units that is Rs 7.1944 per unit. A slab rate off the bill undercollects.
Is it legal for a landlord to charge more than the DISCOM rate per unit?
Charging above the derived average is a common complaint, and several state regulators cap what a landlord may recover from a tenant, so check your state's rules. The proportional method never exceeds the real bill, which makes it defensible.
Does the gap get bigger with higher consumption?
Yes. The gap is the value of the discounted blocks you duplicated plus the top-block units no individual reading reaches, so it widens as the main meter climbs further into the expensive slab.
Sources
- Slab arithmetic in this post was computed from the illustrative three-block tariff stated in the first section (Rs 4.50 / Rs 7.00 / Rs 9.00 in 100-unit blocks), not taken from any one state's tariff order. Verify the blocks against your own bill.
- Telescopic slab billing, fixed charges, meter rent, electricity duty and fuel surcharge line items are standard components of Indian DISCOM domestic bills; the slab table on your bill and your state commission's current tariff order are the authoritative figures.
