Schools are among the best places for solar in Kenya. Most of their electricity is used in daylight, the roofs are large, and every shilling saved on power can go back into teaching. But schools also have a pattern no ordinary bill shows: full days during term, and quiet weekends and holidays. Size the system without allowing for that, and a large share of the panels' output goes unused.
Why the bill misleads
A monthly KPLC bill is an average. Suppose a day school uses about 1,500 kWh a month, 80% of it in daylight. Spread evenly, that is about 40 kWh of daytime use every day, and a calculator would suggest a 10.5 kW array of 17 panels producing about 40 kWh a day.
In reality the school does not use 40 kWh every day. For example, it might use 70 kWh of daylight energy on a busy school day and only 10 kWh on a weekend or holiday, when just the fridges, borehole pump, security lights and staff housing are running. Over a year with about 190 busy days, that adds up to the same bill.
| Spread evenly (bill average) | Following the timetable | |
|---|---|---|
| Solar array | 10.5 kW, 17 panels | 10.5 kW, 17 panels |
| Solar produced per year | about 14,700 kWh | about 14,700 kWh |
| Solar actually used | about 13,550 kWh | about 9,400 kWh |
| Share of output used | 92% | 64% |
| Energy savings per year at the SC3 day rate | about KES 390,000 | about KES 271,000 |
On school days the array cannot cover the full 70 kWh, so the school still buys power. On empty days it produces about four times what the school needs, and without an export arrangement that surplus is wasted. The plain calculation overstated the savings by more than 40%.
Four ways to get more from the panels
- Size for the load that runs every day, then add carefully. A smaller array, say 6.8 kW of 11 panels, uses about 70% of its output in the same school and saves about KES 28,000 a year per kW installed, against about KES 26,000 for the larger array. Each extra panel is worth less than the one before, so add capacity only where the savings justify it.
- Move flexible loads into empty days. Pump the borehole to the tank, run water heaters and freezers, and charge any school bus or staff vehicles on weekends and holidays.
- Ask about exporting surplus. Whether a school can be credited for power it sends to the grid depends on KPLC approval and the terms offered at the time. StimaPulse models an export cap so the plan works with or without it.
- Use a battery for the evening, not for holidays. A battery can carry daytime surplus into evening prep in a boarding school, but it cannot store a holiday's worth of output. Size it for the evening load.
Boarding schools are different
Boarding schools use power from early morning to late night: dormitory lighting, kitchens, evening prep and staff housing. Less of that falls in daylight, so a boarding school with a 4,000 kWh monthly bill and half its use in daylight might need a 21 kW array plus a battery of about 13 kWh to carry evening loads and cover outages. Its savings depend heavily on the CI or SC tariff class and on time-of-use rates, so the evening share needs measuring, not guessing.
What to gather before talking to suppliers
- Twelve months of KPLC bills, so the holiday months show up.
- The school calendar: term dates, weekend use, and any holiday programmes or events.
- A list of loads that run every day: fridges, freezers, pumps, security lighting, staff housing, ICT servers.
- Outage history and what must keep running during one, such as the office, the computer lab during exams and the clinic.
- Roof plans or photos, and any borehole or water tank details.
With those, every supplier can quote against the same need, and the school can compare quotes on cost per kWh actually used rather than panel count alone.
Plan your school's system
- StimaPulse prepares a school decision pack for boards and bursars: load patterns, comparable options, procurement requirements and the engineering review boundary.
- Try a first estimate with the free solar calculator, then adjust for your timetable as above.
- See what a KPLC unit really costs for your tariff class, and the battery backup guide if exam-time outages are a concern.