Last updated: · Reviewed by the lescobillonline.com editorial team
From meter reading to units
A unit is one kilowatt-hour: a thousand watts drawn for one hour. Your meter counts them continuously, and the monthly bill charges the difference between this month's reading and last month's. Nothing is estimated when the reader visits — if a reading is skipped, the bill is marked as estimated and corrected the following month.
This is why two households with identical appliances can receive very different bills. What matters is not what you own but how many hours each appliance runs. A 1.5-ton air conditioner drawing roughly 1.2 kW for eight hours a night adds about 288 units a month on its own, which alone can push a household into a higher slab.
How slabs turn units into rupees
Residential tariffs are slab-based and progressive: the first block of units is cheap, and each subsequent block costs more. Crucially, once total monthly consumption crosses certain thresholds, the higher slab rate is applied to the whole consumption rather than only to the excess. That is why a few extra units at the end of the month can raise a bill sharply.
Protected consumers — those who have stayed under the qualifying monthly consumption for six consecutive months — are billed on a separate, heavily subsidised schedule. Crossing the threshold moves the account to the non-protected schedule, and protection has to be re-earned over six months.
- Slab thresholds are set by NEPRA, not by LESCO, and are revised through public tariff determinations.
- Time-of-use meters split consumption into peak and off-peak units priced separately.
- Commercial and industrial connections use different schedules that also include fixed and demand charges.
What is added on top of the energy cost
These additions routinely account for a quarter to a third of a residential bill, which is why a calculator that prices only units understates the total. A useful estimate applies the slab rate first, then layers the adjustments and taxes on top.
| Line item | What it is |
|---|---|
| Fuel Price Adjustment (FPA) | Monthly correction for the actual fuel cost of generation; can be positive or negative. |
| Quarterly Tariff Adjustment | Periodic true-up applied for several months after a determination. |
| Electricity Duty | Provincial levy charged as a percentage of the energy cost. |
| General Sales Tax | Federal tax on the billed amount. |
| TV Licence Fee | Fixed monthly PTV fee collected through the bill. |
| Late Payment Surcharge | Applied only if you pay after the due date. |
A worked example
Suppose the meter moves from 41,250 to 41,470. That is 220 units. Those units are priced through the applicable residential slab to give the cost of electricity. Fuel price adjustment is then applied per unit, the quarterly adjustment is added, and duty plus sales tax are calculated on the resulting amount. Finally the fixed TV licence fee is added and any arrears carried forward are appended.
Run the same numbers through the calculator on this site and you will see each of those layers separately, which makes it obvious where the money is actually going — and how much a hundred fewer units would have saved.
Helpful tips
- Take your own meter reading on the same day each month; you will spot a wrong reading before it becomes a wrong bill.
- If you are close to a slab boundary, shifting a few high-draw appliance hours into the next billing cycle can save more than it looks.
Warnings & common mistakes
- Any online calculator is an estimate. Government subsidies, protected status and arrears change the final figure.
Frequently asked questions
How many units does an air conditioner use?
A 1.5-ton inverter AC draws roughly 1.0 to 1.5 kW in steady operation, so eight hours a day works out to around 240 to 360 units per month depending on setpoint and insulation.
Why did my bill jump when my units barely changed?
Crossing a slab threshold reprices the entire month's consumption at the higher rate, and a fuel price adjustment swing can move the total independently of your usage.
Is the calculator on this site official?
No. It applies published NEPRA slab rates and standard taxes to give a close estimate; the official bill remains the authoritative figure.
What is FPA on my bill?
Fuel Price Adjustment — a per-unit correction reflecting what fuel actually cost the generators two months earlier. It can be a charge or a refund.
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