Most farm power goes into pumping water or removing heat, often where the grid is weak and the alternative is a diesel generator or petrol pump. Solar fits most of these jobs well, if each is designed around when the energy is needed and what it would otherwise cost. This guide explains the method once, then gives the numbers specific to each use.
The shared method
Store water and cold, not electricity
The cheapest way through the night is usually not a battery. Pumps run while the sun shines and fill a tank; coolers run hard at midday and freeze an ice bank, so the cold is there at dawn and dusk. Tanks and ice banks have no chemical wear and last for decades. Keep batteries for small loads that must never stop, such as incubators, controls and lights.
Compare against diesel at the EPRA price
A small diesel generator burns roughly 0.45 litres of fuel for every kWh it produces, and more when it runs lightly loaded, as farm generators often do. At EPRA's maximum Nairobi pump price of KES 227.76 a litre for diesel (15 October to 14 November 2026), that is about KES 100 per kWh in fuel alone. Super petrol, used in small irrigation pumps, is KES 226.96 a litre. Prices change on the 15th of every month and differ by town, so use your local figure, and add servicing, transport and theft risk. On the grid, compare against your KPLC all-in rate instead: about KES 28.30 per kWh on domestic DC2, or KES 22.09 by day on commercial CI1. Our KPLC cost per kWh guide shows how those rates are built.
Size by season, with July as the low
Across Kenya, each kW of panels produces about 3.83 kWh a day on average (allowing a performance ratio of 0.78), but only about 2.70 kWh a day in July, the weakest month in the overcast June to August period. Divide the daily load by 3.83 for an average-day array and by 2.70 for a July array. Size for July when the load runs all year with no backup; size for the average when the grid or a generator can top up, or when the load peaks in the dry months, as irrigation does. Solar by county shows the monthly sun where you farm, which in the highlands can differ a lot from the national average.
Summary across farm uses
| Use | Typical example | Energy per day | Solar (620 W panels) | Storage | Main alternative |
|---|---|---|---|---|---|
| Borehole pumping | School, 20 m³ at 84 m head | 7.3 kWh | 1.9 kW | 30 m³ water tank | Diesel, about KES 271,000 a year |
| Irrigation from a river or shallow well | One acre on drip | 2.1 kWh | about 0.55 kW, one panel | Raised water tank | Petrol, about KES 136,000 a season |
| Milk cooling | Collection centre, 3,000 litres | about 68 kWh | about 25 kW for July, 41 panels | Ice bank | Diesel, about KES 2.5 million a year |
| Cold room | One tonne of produce a day | about 13 kWh | about 4.9 kW, eight panels | About 50 kg of ice overnight | Diesel, about KES 490,000 a year |
| Poultry | Incubator, LED lighting, pump | 3.6 kWh for the incubator | 2 to 3 kW for a small farm | 5 to 10 kWh battery | Grid with outages |
These are planning estimates using typical efficiencies and equipment ratings; the sections below explain each row.
Each use in detail
Borehole pumping vs diesel
The comparison that matters is cost per cubic metre of water.
Total head. Add the static water level, the drawdown while pumping (from your borehole test report), the discharge height to the tank, pipe friction (often under 2 m; StimaPulse uses the Hazen-Williams method) and any outlet pressure (zero for an open tank, around 10 m for drip).
Energy and sizing. With about 70% pump and 90% motor and drive efficiency, three typical boreholes work out as below. A direct solar pump moves the day's water in the peak sun hours, about 4.9 a day across Kenya, with the array about 25% above motor power for losses and a tank holding about a day and a half of water.
| Borehole | Daily water | Total head | Energy per m³ | Energy per day | Pump motor | Solar array | Tank |
|---|---|---|---|---|---|---|---|
| Home or kiosk | 5 m³ | 46 m | 0.20 kWh | 1.0 kWh | 0.2 kW | 0.3 kW | 8 m³ |
| School or community | 20 m³ | 84 m | 0.36 kWh | 7.3 kWh | 1.5 kW | 1.9 kW | 30 m³ |
| Farm drip irrigation | 50 m³ | 66 m | 0.29 kWh | 14.3 kWh | 2.9 kW | 3.7 kW | 75 m³ |
The examples assume a 30 m water level with 10 m drawdown and a 6 m tank stand for the home, a 60 m level with 15 m drawdown and an 8 m tank stand for the school, and a 40 m level with 10 m drawdown, 5 m lift and 10 m drip pressure for the farm.
Diesel avoided. At 0.45 litres per kWh and KES 227.76 a litre, solar avoids at least:
| Borehole | Diesel per m³ | Diesel per year | Fuel cost per year |
|---|---|---|---|
| Home or kiosk | 0.09 litres | 164 litres | about KES 37,000 |
| School or community | 0.16 litres | 1,191 litres | about KES 271,000 |
| Farm drip irrigation | 0.13 litres | 2,349 litres | about KES 535,000 |
Worked example: cost per cubic metre. Solar has almost no running cost, so its cost per cubic metre is the upfront price spread over the water it delivers:
If a supplier quoted KES 600,000 for the school system, with maintenance at 2% of that a year over 20 years, the water would cost about KES 5.75 per cubic metre. Diesel fuel alone for the same borehole is about KES 37 per cubic metre before servicing. Put each quote into the same formula to compare suppliers like for like.
Pitfalls. A pump bigger than the borehole's safe yield will run it dry. Check the pump curve delivers your design flow at your total head, and keep the generator as backup where supply is critical, such as for livestock. The solar water pumping guide has the full method.
Irrigation from a river, dam or shallow well
Most smallholder irrigation lifts surface water a short way, so it needs far less solar than a borehole. A growing crop uses about 5 mm of water on a hot, dry day, roughly 20 m³ an acre.
| Per acre | Drip at 22 m head | Furrow at 12 m head |
|---|---|---|
| Water reaching the crop | about 90% | about 60% |
| Water pumped per day | about 22 m³ | about 34 m³ |
| Energy per day | about 2.1 kWh | about 1.8 kWh |
| Pump motor | about 0.45 kW | about 0.4 kW |
| Solar array | about 0.55 kW, one panel | about 0.5 kW, one panel |
Drip's 22 m includes about 10 m of drip pressure; furrows fed from a raised tank need about 12 m. Because demand peaks in the dry, sunny months, average-day sizing usually copes; add a second panel per acre if you also irrigate from June to August. A small petrol pump running about four hours a day burns around 4 litres, about KES 900 a day, or about KES 136,000 over a 150-day season.
Keep suction within the pump's limit, usually a few metres, or use a floating or submersible pump, and filter river and dam water before drip lines. Abstraction can require a permit from the Water Resources Authority; leave enough water for people downstream in the dry season.
Milk cooling
Milk leaves the cow at about 35°C and must be cooled to around 4°C, which takes about 0.023 kWh of electricity per litre. The difficulty is timing: cows are milked around 06:00 and 18:00, when solar is weakest. The answer is an ice bank charged at midday; cooling a litre of milk takes about 0.38 kg of ice, so a collection centre's 1,500 litres of evening milk needs about 560 kg, roughly half a cubic metre.
| Small farm | Collection centre | |
|---|---|---|
| Milk per day | 100 litres | 3,000 litres |
| Cooling energy per day | about 2.3 kWh | about 68 kWh |
| Solar for an average day | about 0.6 kW | about 17.7 kW |
| Solar for July | about 0.8 kW | about 25 kW |
- Small farm, off-grid: two 620 W panels run a small DC compressor building an ice bank, with margin even in July. Saving 10 litres a day of evening milk at KES 50 is worth about KES 180,000 a year.
- Collection centre on CI1: about 18 kW (29 panels) sized for the average day saves up to about KES 548,000 a year, with the grid topping up in cloudy months.
- Collection centre off-grid: the same cooling on diesel takes about 30 litres a day, about KES 2.5 million a year. Sizing for July (about 25 kW, 41 panels) with the generator as backup is almost always worth it.
Ask suppliers how fast the cooler brings each milking to 4°C and how many hours the ice bank holds without sun.
Cold rooms for fresh produce
A walk-in room about 3 m x 2.5 m x 2.5 m inside, with 100 mm insulated panel, held at about 8°C and taking in one tonne of produce a day, must remove about 33 kWh of heat a day. With a cooling unit moving roughly 2.5 units of heat per unit of electricity, that is about 13 kWh of electricity a day. Most of it, about 18.4 kWh of the heat, goes into cooling the day's new produce, so pre-cooling in the shade and loading in the cool of the morning both help.
Thirteen kWh needs about 3.5 kW on an average day and about 4.9 kW in July; eight panels produce about 13 kWh in July and about 19 kWh in a typical month. The produce is cooled by day, so at night the room only has to hold temperature, which takes only about 50 kg of ice in this example. Good insulation, a tight door and strip curtains cut the night load further.
The value is in produce saved: cutting losses by 10% on a tonne a day saves 100 kg, about KES 5,000 a day at an example KES 50 a kilogram. Compared with diesel at about KES 100 per kWh, solar also avoids roughly KES 490,000 a year of fuel. Agree crops and temperatures first: leafy greens near 1 to 4°C, avocados around 5 to 7°C, tomatoes and mangoes around 10 to 13°C.
Poultry
Poultry is the one farm use where a battery is the right storage, because the critical load is the incubator. A 500-egg unit uses about 150 W, around 3.6 kWh a day, and a long cut at the wrong time can ruin a hatch. Twelve hours of backup needs about 1.8 kWh usable, about 2 kWh of lithium battery, with an inverter that changes over fast enough that the controller does not reset, and an SMS temperature alarm.
Layers are often given about 16 hours of light; switch to LED poultry lights before sizing, and a small battery covers them easily. Brooding heat is the poor fit: four 250 W lamps running day and night use about 24 kWh a day, about KES 680 a day at the DC2 rate, and would need about ten panels plus a large night battery for a load used only part of each cycle. Insulate the brooder and use electric heating plates instead of lamps, or gas, biomass or charcoal brooders where safe and ventilated.
A small commercial farm with one incubator, LED lighting for a few thousand birds, a water pump filling a header tank and an office might need about 2 to 3 kW of panels and 5 to 10 kWh of battery, with brooding handled separately.
Next steps
- Estimate panels, battery and inverter for any daily load with the free solar calculator.
- For a generator you want to run less, read diesel generator vs solar hybrid.
- Size incubator and essential-load backup with the battery backup guide, and choose chemistry with lithium vs lead-acid.
- Check the return with the solar payback guide, then compare quotes and financing options.
- For a cooperative, collection centre or borehole, request an assessment with your test report, fuel use and bills.