To work out a sub-meter bill, take the current reading minus the previous reading to get the units, then divide the main bill by the main meter's units and multiply by the sub-meter units. With a Rs 11,436 bill for 228 units at September 2026 rates, each unit costs Rs 50.16, so a portion that used 98 units pays about Rs 4,915.
Enter the main bill and each sub-meter's two readings above. The calculator gives every portion its share, including the part of the house that has no sub-meter, and lets you compare four common ways of splitting the bill.
How to calculate a sub meter reading
A sub-meter counts units the same way as the company meter. Read the kWh figure on the day the main meter is read, which is the reading date printed on your bill.
- Write down last month's reading, for example 4,512.
- Read the meter today, for example 4,610.
- Subtract: 4,610 minus 4,512 = 98 units.
On a digital meter, cycle through the display until you see the total kWh register, on many meters marked kWh or with the code 1.8.0. Ignore readings shown as kW, voltage or current. If the new reading is smaller than the old one, the meter has passed 99999 and started again from zero, so add 100,000 to the new reading before you subtract.
The units on the main bill minus all the sub-meters is what the rest of the house used. The calculator does this subtraction for you.
Four ways to split the bill
1. Average rate per unit
Divide the whole bill by the main meter's units and charge every portion that rate. Each portion carries its share of fixed charges, adjustments and taxes in proportion to what it used. This is the simplest method and the one most landlords use.
2. Fixed charges split equally
Fixed charges depend on sanctioned load, not on units, so some families split them equally and share the rest of the bill by units. Enter the fixed charges line from your bill.
3. Each portion at its own slab
This charges the sub-meter as if it were a separate company meter, using the NEPRA tariff for its own units. A small portion then pays a low slab rate, and the rest of the house pays whatever is left. It shows what the tenant would pay with a meter of their own.
4. Agreed rate per unit
Many rental agreements fix a rate, such as Rs 50 a unit. The tenant pays units times that rate and the owner pays the balance. Check the agreed rate against the real average each month, because fuel adjustments change it.
Worked example: one bill, four methods
This is the example loaded in the calculator. The main bill is for 228 units on a 2 kW unprotected connection at current rates. The upper portion's sub-meter went from 4,512 to 4,610, so it used 98 units. The rest of the house used 228 minus 98 = 130 units.
| Method | Upper portion (98 units) | Rest of the house (main meter less sub-meters) (130 units) |
|---|---|---|
| Average rate per unit | Rs 4,915 | Rs 6,521 |
| Fixed charges split equally | Rs 4,965 | Rs 6,471 |
| Each portion at its own slab | Rs 3,634 | Rs 7,802 |
| Agreed rate per unit | Rs 4,900 | Rs 6,536 |
The average rate is the bill divided by 228 units, which is Rs 50.16 per unit, so the upper portion pays 98 x 50.16. Under the own slab method the upper portion is billed as a 98-unit meter at the first unprotected slab rate of Rs 22.44, with 1 kW of fixed charges, adjustments and taxes on top. The rest of the house then pays the balance, which is far more per unit, because 228 units together fall into the 201 to 300 slab.
Why one meter for two families costs more
For unprotected homes, every unit is charged at the rate of the slab the month's total falls in. Two families on one meter push the total into a higher slab, so all units cost more.
In the example above, 228 units on one meter come to about Rs 11,436. The same 98 and 130 units on two separate meters of 1 kW each would come to about Rs 3,634 and Rs 5,751, a total of Rs 9,385. That is about Rs 2,050 a month saved just by metering the portions separately. Use the electricity bill calculator to check the numbers for your own units.
What the rules say about sub-meters
Your electricity company bills only its own meter. A private sub-meter has no standing with LESCO, MEPCO, IESCO, K-Electric or any other company, so any split is a private arrangement between the owner and the tenant. Rules and practice also differ between companies and landlords.
NEPRA's Consumer Service Manual expects a separate connection for each separate household. A second connection in the same building is allowed where the portion has its own circuit, its own kitchen and its own entrance, backed by an affidavit on a Rs 50 stamp paper that a separate family lives there. Both connections should come from the same transformer. A tenant can apply for a connection in their own name with a no objection certificate from the owner.
If sub-meter readings are a regular source of argument, a separate meter usually settles it, and as shown above it often lowers the total bill.
This calculator splits the bill you enter. It does not check your bill. Leave out arrears, instalments and late payment surcharge before splitting, and agree them separately. A cheap sub-meter can read a few percent high or low, so compare the total of all sub-meters with the main meter now and then.
Sub-meter questions
How do I calculate an electricity bill from a sub-meter reading?
Subtract last month's sub-meter reading from this month's to get the units used. Divide the total bill by the units on the main bill to get the average cost per unit. Multiply that by the sub-meter units. For example, Rs 11,436 for 228 units is Rs 50.16 a unit, so 98 sub-meter units cost about Rs 4,915.
Should the tenant pay the slab rate or the average rate?
The average rate is fairer when both families share one meter, because both push the total into the same slab. Charging the tenant only their own low slab rate leaves the owner paying the higher slab on every unit. Charging a high fixed rate can do the opposite. The calculator shows all four methods so both sides can see the difference.
Why do the sub-meters not add up to the main meter?
Usually because the readings were taken on different days. Read every sub-meter on the same day the company reads the main meter. Wiring losses and the accuracy of cheap sub-meters also cause small gaps. Any units left over are shown as the rest of the house, so they are not lost from the split.
Can a tenant get a separate electricity meter?
Yes, in most cases. NEPRA's Consumer Service Manual allows a separate connection for a portion with its own circuit, kitchen and entrance. The applicant gives an affidavit that a separate family lives there, and a tenant also needs a no objection certificate from the owner. Your electricity company's office will list its own documents and fees.
Who pays the fixed charges on a shared meter?
There is no fixed rule, so agree it in writing. Using the average rate, fixed charges are shared by units along with everything else. With the fixed split method, each portion pays an equal part of the fixed charges and the rest of the bill is shared by units. Enter the fixed charges line from your bill to see both.
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Last reviewed 29 September 2026. Results are estimates; official notices always take precedence.