Commercial and industrial (CI) customers of Kenya Power pay for electricity in two ways: for the energy they use, in kWh, and for their maximum demand, in kVA, the highest load their meter records during the month. The second charge is easy to overlook, and it behaves very differently from the first. Solar panels are excellent at cutting the energy charge but often leave the demand charge untouched.
What the demand charge costs
These are the reviewed demand charges StimaPulse uses, per kVA of maximum demand per month, before VAT:
| Customer class | Demand charge per kVA per month |
|---|---|
| CI1 (415 V) | KES 1,100 |
| CI2 (11 kV) | KES 700 |
| CI3 (33 kV) | KES 370 |
Domestic, small commercial and e-mobility connections do not pay a demand charge.
How big a share of the bill it is
Take a CI1 factory that uses 30,000 kWh a month, 80% of it during the day, with a maximum demand of 150 kVA:
| Bill item | Calculation | KES per month |
|---|---|---|
| Daytime energy | 24,000 kWh at KES 22.09 all-in | 530,160 |
| Night energy | 6,000 kWh at KES 13.96 all-in | 83,760 |
| Demand charge | 150 kVA at KES 1,100 | 165,000 |
The demand charge is about 21% of the bill, and it is set by the single highest moment of the month. If two compressors, a kiln and the borehole pump all start together for a few minutes once in thirty days, that moment sets the charge for the whole month.
Why solar alone rarely reduces it
A 100 kW solar array on that factory would produce about 140,000 kWh a year, worth about KES 3.1 million a year at the daytime rate if all of it is used on site. That is a strong energy case. But the demand charge only falls if the array is producing strongly at the exact moment of the month's peak, every month. Peaks often happen at shift start around 07:30, when solar is weak, or on a cloudy afternoon. One peak without sun and the month's demand charge is unchanged.
There is a second subtlety: KPLC bills demand in kVA, not kW. Solar inverters normally supply real power (kW) only, so the grid still supplies the reactive power that motors need. Solar can lower the kW drawn from the grid without lowering the kVA as much as expected.
Four ways to cut the demand charge
- Correct the power factor. kVA is kW divided by power factor. At a power factor of 0.80, a 120 kW load draws 150 kVA. Raise it to 0.95 with a capacitor bank and the same load draws about 126 kVA, saving about 24 kVA, or roughly KES 26,000 a month at the CI1 rate, before touching anything else. Your bill or a power quality logger shows your current power factor.
- Stagger large motor starts. Start compressors, pumps and mills a few minutes apart, and move non-urgent loads away from the busiest hour. Timers and simple interlocks often cost far less than any equipment.
- Shave peaks with a battery. A battery that supplies 30 kW for up to an hour during the factory's peaks could cut maximum demand from 150 to 120 kVA, saving KES 33,000 a month, about KES 396,000 a year. That needs about 30 kWh of usable storage (about 33 kWh nominal) and, critically, a controller that catches every peak: one missed peak sets the charge for that month.
- Schedule flexible loads. Pumping to a tank, pre-cooling cold rooms and charging forklifts can move to hours when the rest of the plant is quiet.
Before you invest
- Get twelve months of bills and note the maximum demand and power factor each month.
- Ask Kenya Power or an electrician for interval meter data, or log the load for at least two weeks, to see when peaks happen and what causes them.
- Fix power factor and motor scheduling first; they are usually the cheapest kVA.
- Then size solar for the daytime energy, and a battery for the remaining peaks only if the savings justify it.
Model your own bill
- Kenya electricity tariffs lists the reviewed energy and demand rates for every class.
- The commercial and industrial solar guide shows how StimaPulse separates energy, demand and levy savings so finance teams can check them.
- See the battery backup and storage guide for usable capacity and inverter sizing, and what a KPLC unit really costs for the all-in energy rates used here.