Lodges, shops, workshops, farms and camps beyond the grid often run on a diesel generator for most of the day. It works, but it is one of the most expensive ways to make electricity. A solar and battery hybrid, with the generator kept for backup, usually cuts the fuel bill by far more than it costs to install.
What a generator unit really costs
A small diesel generator burns roughly 0.45 litres of fuel for every kWh it produces, and more when it runs lightly loaded, as off-grid generators often do overnight. At KES 227.76 a litre, EPRA's maximum Nairobi pump price for 15 October to 14 November 2026:
That is more than three and a half times the KES 28.30 a domestic KPLC customer pays all-in, before counting servicing, oil, filters, transport of fuel to site, theft and the generator's own replacement.
The example business
An off-grid lodge or workshop uses about 40 kWh a day: 24 kWh during daylight (kitchen, workshop tools, pumping, office) and 16 kWh in the evening and overnight (lighting, refrigeration, security, guest rooms).
Running everything on the generator takes about 6,600 litres of diesel a year, about KES 1.5 million in fuel at that price.
Option 1: solar for the daytime only
Eleven 620 W panels (6.8 kW) with a suitable inverter cover most of the daytime load directly. The generator still runs every evening and on cloudy days.
Option 2: a full hybrid
Eighteen 620 W panels (11.2 kW) produce enough to run the daytime load and charge a battery for the evening. With about 16 kWh of usable battery (about 17.8 kWh nominal for lithium), the generator is needed only when the sun falls short, mostly in the cloudy months.
| Generator only | Solar for the daytime | Full hybrid | |
|---|---|---|---|
| Solar array | none | 6.8 kW | 11.2 kW |
| Battery (usable) | none | none | 16 kWh |
| Energy from the generator | 100% | about 42% | about 5 to 10% |
| Diesel per year | about 6,600 litres | about 2,800 litres | about 350 to 660 litres |
| Fuel cost per year | about KES 1.5 million | about KES 634,000 | about KES 79,000 to 150,000 |
The hybrid's range reflects the weather. Using Kenya's average month, the generator would supply about 5% of the energy, almost all of it between May and August. Real weather comes in runs of cloudy days, so plan for closer to 10%.
Month by month
On Kenya's average solar resource, the 11.2 kW hybrid needs no generator from September to April. In July, the weakest month, the array produces about 30 kWh a day against the 41 kWh needed after battery losses, so the generator fills a gap of about 10 kWh a day. Your county may be sunnier or cloudier in those months; check the solar by county pages.
What it pays back
Prices vary widely by site and equipment, so take these only as an example. If the full hybrid cost KES 1.7 million installed and saved about KES 1.35 million of fuel a year (planning for 10% from the generator), it would pay back in about 15 months from fuel alone. Diesel prices change every month, so rerun the figures with the latest EPRA price. The generator also runs far fewer hours, so servicing costs fall and its life is extended.
Because diesel is so expensive, the case for solar is usually stronger off-grid than on the grid. The bigger risk is undersizing: a battery too small for the evening load, or an array that leaves the generator running every afternoon in July.
Getting the hybrid right
- Measure the evening load carefully. It sets the battery size, and refrigeration and lighting add up.
- Use an inverter that can start the generator automatically when the battery runs low, and charge the battery from it efficiently.
- Keep the generator properly sized and serviced. It now runs less often, but it must start when needed.
- Move flexible loads into the day: pumping, laundry, workshop machines and charging.
- Plan for the dry and cloudy seasons separately, since water and power demand can peak at different times.
Size it for your site
- The free solar calculator sizes panels, battery and inverter from your load and backup hours.
- The battery backup and storage guide covers usable capacity and generator integration, and our solar borehole pump vs diesel article does the same comparison for water pumping.
- For a full hybrid design with monthly simulation and supplier comparison, request an assessment.