Every farmer who asks us about our solar water pumps (from KSH 20,000) is really asking one question: will this actually save me money, or is it just a trendier way to move water?
The honest answer is that solar usually wins, but not always, and the cases where it loses are predictable enough that you can work out which side you fall on before you spend anything. This guide gives you the arithmetic, the sizing method, and the mistakes that turn a good solar decision into an expensive one.
If you have not yet settled on a pump type at all, start with our guide to choosing the right water pump, then come back here once solar is on your shortlist.
The trade you are actually making
A solar pump costs more to buy and nothing to run. A petrol pump costs less to buy and something to run every single day it works. That is the entire decision, and it means the question is not "which is cheaper?" but "how long until the fuel I stop buying pays back the extra I spent?"
That break-even point is the number worth calculating, because it turns a vague preference into a date. Before it, the petrol pump was the cheaper choice. After it, every litre you do not buy is money you keep, for as long as the pump lasts.
The sun does not send an invoice. That single fact is what changes the maths, and it is why a pump that runs most days behaves completely differently on paper from one that runs occasionally.
Working out your own break-even
You need three numbers, and you already know two of them.
One: the price gap. What the solar system costs, complete, minus what the petrol pump costs. Complete matters. A solar pump is a panel, a controller and a pump, and quoting only the pump is how people end up surprised.
Two: your fuel burn. How many litres your petrol pump gets through in a typical week, multiplied by what you actually pay at the pump. Not the headline price, the price at your nearest station including the trip to fetch it.
Three: divide one by the other. Price gap divided by weekly fuel cost gives you the number of weeks until the solar system has paid for itself. That is your break-even.
Most farms pumping most days find that figure lands inside a year or two of regular use. Farms pumping once a fortnight find it lands years out, which is the honest signal that petrol is still their answer.
A worked example
Numbers make this concrete, so here is the method applied. Treat the figures as a worked illustration rather than a quotation, and substitute your own.
Suppose a farmer runs a petrol pump for roughly two hours every morning to irrigate a plot and fill livestock troughs. Say that burns around four litres a week. Whatever fuel costs at their nearest station, they multiply four by that price and get a weekly fuel bill.
Now suppose the complete solar system, pump and panel and controller together, costs a certain amount more than replacing the petrol pump would. Divide that price gap by the weekly fuel bill and the answer comes back in weeks.
The useful part is what the answer does to the decision. If it lands at thirty weeks, the farmer is buying free water from month eight onward, for as long as the panel lasts, which is usually measured in decades rather than years. If it lands at three hundred weeks, solar is not wrong exactly, but it is not urgent, and the money is probably better spent elsewhere on the farm this season.
Two adjustments make the estimate honest. Add the servicing a petrol engine needs and the solar side does not, because that is real money on the same side of the ledger as fuel. And subtract nothing for the trips to fetch fuel, but remember them, because the time cost is real even when it never appears in the arithmetic.
Matching the system to how you actually farm
The same borehole supports very different systems depending on what the water is for. Livestock demand is steady and predictable, which suits solar well: the herd drinks about the same volume daily, so a modest pump running through the day into a tank covers it comfortably.
Irrigation is spikier. Demand concentrates into the dry months, which is also when sunshine is most reliable, so the seasons align in solar's favour. The risk is sizing for the average rather than the peak and then finding the system short in the weeks that matter most.
Household supply is the least demanding in volume but the least forgiving in reliability, because nobody accepts a dry tap. That is the clearest case for generous storage rather than a bigger pump.
Where petrol or electric still makes sense
- Occasional, high volume needs. If you need to move a lot of water quickly, on demand, regardless of weather or hour, a petrol pump's flexibility outweighs solar's running cost advantage.
- Heavily shaded sites. Solar output depends on sun reaching the panel. A borehole under permanent tree cover will never give you the performance the panel is rated for.
- Very low, infrequent usage. If you pump a few times a month, the fuel you save may never add up to the extra you spent.
- Reliable mains already at the pump head. Where three phase power is already present and stable, an electric pump can beat both on cost per litre moved.
Sizing: the part that decides whether it works
More solar pumps disappoint because of sizing than because of quality. A pump is not chosen by wattage. It is chosen by the job, and the job has three measurements.
Head is the vertical distance the water must climb, from the water level in the borehole to the highest point it must reach, including the tank stand. Head is the measurement people underestimate most, because they measure to the tank and forget the stand it sits on.
Flow is how much water you need per day, in litres. Work it from actual demand: livestock counts, irrigated area, household use. Guessing high here is expensive, because you pay for capacity you never use.
Borehole yield is how fast the hole itself can give water up. A pump that outpaces its borehole will draw the level down and run dry, which damages the pump. The borehole sets a ceiling no pump can exceed.
Notice that the panel is sized last. Buying a panel first, then hunting for a pump to match it, is the most common way farmers end up with a system that underperforms in exactly the season they need it.
The tank is the battery
This is the single most useful idea in solar pumping, and it is the one most often missed.
A solar pump only works when the sun is on the panel. That sounds like a limitation until you realise you do not need water at the moment it is pumped. You need it available when you turn a tap. So you pump into an elevated storage tank through the day, and draw from that tank by gravity whenever you like, including at night and through a cloudy morning.
The tank does the job a battery would do, at a fraction of the cost, with nothing to degrade. A few days of storage turns an intermittent supply into a reliable one. It is also why a tank and stand should be budgeted as part of the system rather than treated as an extra.
Storing water is far cheaper than storing electricity. If you are being sold batteries for a solar pump, ask why a bigger tank will not do the same job for less, because in most farm installations it will.
What actually goes wrong
Dirty panels. Dust is the quiet thief of solar output, and Kenya has plenty of it. A panel washed occasionally holds its performance. One left through a dry season does not.
Shading that arrives later. A site with clear sun in January may sit in tree shadow by June as the sun angle shifts. Check the site across the day and think a season ahead.
A pump outrunning its borehole. Running dry is the fastest way to destroy a submersible. This is why we ask about yield before recommending a unit rather than selling on wattage.
Undersized cable. Long runs of thin cable lose voltage before it reaches the pump, and the symptom looks exactly like a weak panel. It is cheap to get right at installation and irritating to fix afterwards.
Maintenance is genuinely lighter
Solar pumps have fewer parts that wear. There are no spark plugs, no fuel lines and no engine oil to change. Panels need periodic cleaning and the system needs an occasional look at connections. That is largely it.
A petrol pump, by contrast, needs servicing on a schedule, and the parts that wear are the parts that strand you when they fail. Neither is maintenance free, but the solar side asks less of you and asks it less often.
Key takeaways
- The decision is upfront cost against running cost. Calculate your break-even and it stops being a matter of opinion.
- Pumping most days favours solar strongly. Pumping occasionally often still favours petrol.
- Size in order: daily need, head, flow against borehole yield, then pump, then panel. Never start at the panel.
- Budget the storage tank as part of the system. It does the job of a battery for less money and lasts longer.
- Shade, dust, borehole yield and cable size cause more disappointment than pump quality does.
Frequently asked questions
Does a solar pump work on a cloudy day? It works, but more slowly, because output follows available sunlight. This is exactly why the storage tank matters: a few days of stored water means a cloudy stretch changes nothing at the tap.
Do I need batteries? Usually not. Storing water in a tank is cheaper than storing electricity in batteries, and a tank has nothing to degrade. Batteries make sense only when you must pump at night for a specific reason.
How deep can a solar pump draw from? That depends on the pump, not on solar as a technology. Head is a pump specification, so the honest answer requires your borehole's water level and total lift. Tell us those and we will match a unit to them.
What does a complete system cost? Our 100W solar water pump starts at KSH 20,000, and a complete installation also includes the panel, controller, piping and usually a tank and stand. We quote the whole system rather than the pump alone, because a pump-only price is not a number you can plan with.
Can I run an existing pump from solar? Sometimes, but it is often false economy. Pumps designed for solar are built to run efficiently on variable power. A mains pump driven through a converter usually wastes enough energy to cancel the saving.
Our recommendation
If you pump water most days, for irrigation, livestock troughs or household supply, solar is very likely the right call, and the fuel you stop buying is the reason. If your usage is occasional and unpredictable, a petrol pump's on demand flexibility may still serve you better.
Tell us your borehole depth, your daily water need and your site conditions, and we will size a system honestly, including telling you when solar is not the right answer for your situation. We would rather lose a sale than sell you a pump that disappoints you in the dry season.
