For a home using 300 kWh of electricity a month, you need roughly 2.4 to 2.8 kW of solar panels in most Kenyan and Tanzanian towns: six or seven 400 W panels, with a battery of about 4 kWh. The exact figure depends on how many hours of strong sun your town gets, and that is what this guide works through, town by town.
Every figure below comes from our free solar estimator, the same one behind our town pages, using long-term sun data for each town (Global Solar Atlas) and our October 2026 equipment prices. They are estimates to plan with, not quotes.
The three numbers that decide your system
- How much electricity you use, in kWh a month. Your bill or token history shows it. This matters more than anything else.
- Your town's sun hours: the number of hours a day of full-strength sun your panels effectively get, averaged over the year. Kenyan towns range from about 5.3 in Nairobi and Embu to about 6.4 in Lodwar.
- How much backup you want: that decides the battery, not the panels.
Finding your monthly kWh
Everything starts from how many kilowatt-hours (kWh) you use in a month. Three ways to find it:
- Postpaid bill: the units consumed are printed on it. Take the average of the last few months, because use changes with the season.
- Prepaid tokens: add up the units on the token messages for a full month, or check your purchase history.
- From what you spend: divide your monthly spend by the price per unit. It is less accurate, because the price per unit includes charges that change, so use units if you can.
If you are planning a new house, estimate from a similar home, then add any big new appliances such as a borehole pump.
How the size is worked out
The method is simple enough to check by hand:
- Daily use = monthly kWh ÷ 30. At 300 kWh a month that is 10 kWh a day.
- Panel size = daily use ÷ sun hours, then allowing about 24% for real-world losses in wiring, the inverter, dust and light shade. Round up to whole 400 W panels.
- Battery = enough usable storage for about 40% of a day's use, which covers evenings and short outages.
So in Nairobi, 10 kWh a day ÷ 5.31 sun hours, with losses, needs about 2.5 kW; rounded up to whole panels, that is seven 400 W panels, or 2.8 kW.
Town by town: a home using 300 kWh a month
| Town | Sun hours | Panels | System | Indicative cost | Payback |
|---|---|---|---|---|---|
| Nairobi | 5.31 | 7 | 2.8 kW | KSh 262,700 | 4.1 yrs |
| Nyeri | 5.45 | 7 | 2.8 kW | KSh 262,700 | 4.1 yrs |
| Mombasa | 5.67 | 6 | 2.4 kW | KSh 245,700 | 3.9 yrs |
| Garissa | 5.69 | 6 | 2.4 kW | KSh 245,700 | 3.9 yrs |
| Kisumu | 6.19 | 6 | 2.4 kW | KSh 245,700 | 3.9 yrs |
| Eldoret | 6.19 | 6 | 2.4 kW | KSh 245,700 | 3.9 yrs |
| Lodwar | 6.43 | 6 | 2.4 kW | KSh 245,700 | 3.9 yrs |
| Dar es Salaam | 5.36 | 7 | 2.8 kW | TSh 5,293,000 | 6.3 yrs |
| Arusha | 5.45 | 7 | 2.8 kW | TSh 5,293,000 | 6.3 yrs |
| Dodoma | 6.34 | 6 | 2.4 kW | TSh 4,951,500 | 5.9 yrs |
Each system includes a battery of about 4 kWh usable and installation. Payback assumes solar replaces about 80% of your bill, at KSh 22 per kWh in Kenya and TSh 292 per kWh in Tanzania. If you pay more per unit, solar pays back sooner.
Two things stand out. Sunnier towns need one panel fewer for the same use, which is why Kisumu, Eldoret and Lodwar come in below Nairobi. And the difference is smaller than people expect: most of the cost is the battery, the inverter and the installation, which do not change with the sun.
How the size grows with your use (Nairobi)
| Monthly use | Panels | System | Battery | Indicative cost | Payback |
|---|---|---|---|---|---|
| 150 kWh (a small home) | 4 | 1.6 kW | 2 kWh | KSh 145,650 | 4.6 yrs |
| 300 kWh (a family home) | 7 | 2.8 kW | 4 kWh | KSh 262,700 | 4.1 yrs |
| 600 kWh (a large home or small shop) | 13 | 5.2 kW | 8 kWh | KSh 496,500 | 3.9 yrs |
Bigger systems pay back slightly faster, because the fixed costs are spread over more savings.
Grid-tied, hybrid or off-grid?
- Grid-tied, no battery: the cheapest system, but it switches off in a blackout, and it only saves money on what you use while the sun shines.
- Hybrid, with a battery: the usual choice for homes and shops on the grid. It uses solar first, stores some for the evening, and keeps essentials running in an outage. All the figures in this guide are for a hybrid system.
- Off-grid: for a plot with no mains power. It needs a much bigger battery, sized for several days of cloud, and careful planning of what runs when.
What can change your numbers
- Shade. Trees, water tanks and taller buildings cut what a panel produces, even with partial shade. Keep the panel area clear.
- Roof direction and tilt. Near the equator these matter less than in Europe, but a steep roof facing the wrong way still costs output.
- When you use power. Solar produces in the day. If most of your use is at night, you need a bigger battery, not more panels.
- Equipment prices. These move. Treat the costs as a guide and get two or three itemised quotes.
Get your own figure
Enter your town and your monthly bill or units, and the free solar estimate gives you the system size, battery, an indicative installed cost, the payback period and a materials list, with no account needed. Units (kWh) give a sharper answer than the bill.
This information is given as a guide. Confirm it before you use it, and adapt it to your own situation.
Common questions
How many solar panels does a 3-bedroom house need?
It depends on use, not bedrooms. A family home using about 300 kWh a month needs six or seven 400 W panels in most Kenyan towns.
Can solar run my whole house?
It can cover most of it. Our estimates assume solar replaces about 80% of what you buy from the grid; cookers, water heaters and irons are best run in daylight or left on the grid.
How long does a solar system last?
Panels typically carry 20 to 25 year performance warranties; inverters and batteries are usually replaced sooner. Check each warranty on your quote.
Is Nairobi sunny enough for solar?
Yes. At about 5.3 sun hours a day, Nairobi gets far more usable sun than most of Europe, where solar is common.