Electrical load calculator
Four different numbers get called “load” and confusing them is expensive. Connected load is everything wired in. Peak demand is what actually coincides. kVA is what generators and UPS units are rated in. And sanctioned load is what your distribution company has approved — and, where fixed charges are levied per kilowatt, what you pay for every month whether you draw it or not.
What is connected
Count everything wired in, including things you rarely use. This total is what a DISCO survey records as connected load.
| Item | Watts each | How many | Total W | Remove |
|---|---|---|---|---|
| Lighting point (LED) | 144 | |||
| Ceiling fan | 325 | |||
| Refrigerator | 160 | |||
| Air conditioner 1.5 ton | 3,600 | |||
| Electric geyser | 2,000 | |||
| Water pump 1 HP | 950 |
Typical Pakistani households run 40 to 55 per cent diversity — the summer evening peak, when the air conditioners, the fans and the lights coincide. Sites with large motors run a lower power factor; resistive loads such as geysers and heaters sit close to 1.
Load summary
3.23 kW realistic peak
- Connected load (everything, as surveyed)7.18 kW
- Peak demand at 45% diversity3.23 kW
- Apparent power at PF 0.853.8 kVA
- Current, single phase at 230 V17 A
- Current, three phase at 400 V5 A
- Sanctioned load to apply for4 kW
- Supply type indicatedSingle phase is adequate
The suggested sanction adds 15 per cent headroom to the realistic peak. Sanctioning far above that costs money every month wherever fixed or demand charges are levied per kilowatt; sanctioning below it risks an unauthorised-load finding at inspection. For a generator or UPS, size on the kVA figure and allow extra for motor starting surge.
Connected load counts everything; nothing runs everything
A DISCO survey adds up the rated power of every point and every fixed appliance without asking whether they could all run together. That total is connected load, and for a Pakistani household it is typically twice or more what the house ever actually draws.
The diversity factor bridges the two. At 45 per cent, a house with 12 kW connected has a realistic peak of about 5.4 kW — the summer evening when the air conditioners, the fans and the lights coincide but the geyser, the iron and the pump do not.
Why kVA is bigger than kW
Motors, transformers and fluorescent ballasts draw current that does no useful work but still has to be supplied. Power factor is the ratio between the useful part and the total, and dividing kW by it gives kVA.
This matters for two purchases. A generator rated 10 kVA delivers only 8 kW at a power factor of 0.8, which is why one that comfortably ran heaters struggles with motors. And on industrial tariffs where demand is charged in kVA, poor power factor inflates the billed demand for identical output.
Sanctioning too much and too little both cost
Above what you need, every extra kilowatt is a standing monthly charge wherever fixed or demand charges are load-based. Reducing a sanction is a formal application with an inspection, and the saving then continues indefinitely.
Below what you draw, the exposure is an unauthorised-extension-of-load finding at inspection, with an assessment attached. It also blocks a net-metering application, because NEPRA caps system size against the sanctioned figure.
The suggested sanction here adds 15 per cent headroom to the realistic peak, which is the balance between those two failure modes.
When three phases become necessary
Single-phase domestic services in Pakistan are commonly limited to somewhere around 15 kW. Beyond that, and for any motor above roughly five horsepower, three-phase supply is the practical route.
It is not cheaper per unit. Domestic three-phase connections are billed on a different schedule and do not pick up the single-phase protected slabs — a point that surprises households who upgrade expecting a saving.
Frequently asked questions
What diversity factor should I use for a Pakistani house?
Between 40 and 55 per cent for a typical household. Use the higher end if you run multiple air conditioners simultaneously through the summer evening, and the lower end if your heavy loads — geyser, pump, iron — are naturally staggered through the day.
How do I size a generator or UPS from this?
Use the kVA figure, then add headroom for motor starting surge, which can be several times running current on a refrigerator compressor or a water pump. For a UPS, also check the battery: capacity in amp-hours times battery voltage times a usable depth of discharge of about 50 per cent gives the watt-hours actually available, and that is usually the real limit rather than the inverter rating.
How do I find out my current sanctioned load?
It is on the connection agreement and in the account file at your sub-divisional office. Commercial and industrial bills print it in the header; small domestic bills frequently do not.
Does a higher sanctioned load raise my domestic bill?
On an ordinary energy-only domestic tariff you pay for units, so it does not directly. It matters wherever fixed or demand charges are levied per kilowatt, and it determines the maximum solar system size you can have approved.
Related
A planning aid, not a design. Cable sizing, protection coordination and earthing are engineering decisions for a qualified electrician, and any application to change a sanctioned load involves a DISCO survey that supersedes this estimate. Use it to arrive at that conversation with a defensible number.