Solar tubewells and agricultural systems

Agricultural solar is the one category on this site where most of the net billing discussion is irrelevant. A tubewell on remote land usually has no grid connection to export to, so there is no buyback rate, no distribution company application and no metering question. There is a borehole, a water requirement and a fuel bill.

That makes the design cleaner and the economics unusually strong — but it also means most of the sizing advice circulating in Pakistan, which is written for rooftop grid-tied systems, does not apply.

The design unit is water, not watts

The most common specification error I see on farms is sizing the array from the existing pump nameplate. Existing pumps are frequently oversized — they were bought to a round number, or inherited, or specified for a well that has since deepened. Copying that rating into a solar design produces a system considerably larger and more expensive than the duty requires.

The correct starting point is two numbers: how many cubic metres per day you actually need to deliver, and the total dynamic head — the real lift from water level to discharge, including friction, not the depth of the borehole. From those, the hydraulic power is arithmetic, and the array follows from the hydraulic power across the usable solar day.

Against diesel, the arithmetic is not close

A grid-tied rooftop system displaces units at your tariff slab. A solar tubewell displaces diesel — a far more expensive unit, bought at fluctuating prices, with the transport, the pilferage and the engine maintenance that come with it.

That is why agricultural payback figures often look implausible to people used to rooftop numbers. They are not implausible; they are measured against a different alternative. What I will not do is quote you one without knowing your actual monthly diesel consumption, because the whole calculation rests on it.

What remote land does to a design

• Theft is a real design input. Module clamping, fastener choice and site security change the specification, and pretending otherwise is how farms lose an array in the first year.
• Livestock and grazing determine mounting height and cabling routes far more than aesthetics do.
• Dust loading in agricultural settings is heavier than on urban rooftops, so cleaning access and water availability are part of the design conversation rather than an afterthought.
• Serviceability matters more when the site is two hours from anywhere. Simpler is better, and a controller nobody can source locally is a bad choice regardless of its efficiency figure.

Farms that do have a connection

Not every agricultural site is off-grid. Where a farm has a connection — and particularly where there is a processing operation attached, a chilling unit, a rice husking plant, a cold store for produce — the calculation changes and starts to look more like the industrial one.

Two things are worth getting right there. First, the processing load is usually far more valuable to offset than the pumping load, because it runs longer and draws more consistently; sizing around the tubewell alone can leave the better opportunity untouched. Second, since February 2026 exported units are bought back at roughly a third of the old rate, so surplus generation during a season when the pump is idle is worth much less than it once was.

That seasonality is the specifically agricultural version of the sizing problem. A system sized for peak irrigation demand spends the off-season exporting cheaply. It is often better to size closer to the year-round baseline — the processing and chilling load — and accept that the pump draws from the grid at the peak of the season.

Keeping the diesel set

On most farms I recommend keeping the existing diesel engine rather than removing it, at least initially. It costs nothing to leave in place, it covers the genuinely cloudy days in a critical irrigation window, and it means the decision to go solar does not have to carry the risk of a bad monsoon week. Hybrid here is a risk decision, not a technical one.