Kenya Solar Irrigation Loan Planner

Introduction

Solar irrigation is often discussed as a climate-smart upgrade, but a farmer or lender still has to answer a practical question before buying a pump: will the extra water create enough cash to justify the upfront cost and the loan repayments? That is exactly what this planner is built to clarify. It combines equipment cost, grant support, down payment, interest rate, crop water demand, expected yield improvement, and crop price into one cash-flow view. Instead of looking at the solar pump as a stand-alone machine, the page treats it as a farm investment that must serve crops, protect household liquidity, and satisfy a financing agreement at the same time.

The calculator is especially useful in Kenyan settings where the path to purchase is mixed. A farmer may receive a development grant, a county subsidy, results-based financing support, or a concessional asset loan from a SACCO, microfinance institution, or specialist solar company. Those arrangements change the financed amount materially. A grant reduces the principal immediately, while a larger down payment lowers the loan burden but raises the farmer's day-one cash requirement. The planner makes those trade-offs visible, which is helpful when comparing vendor quotes or discussing tenor and interest with a lender.

Water delivery is just as important as finance. A pump can only create value if it delivers useful water to the crop. The form therefore asks for pump capacity, expected operating hours during the irrigation season, acreage in hectares, irrigation days per year, and crop water requirement in millimetres per day. From there, the tool converts agronomic demand into cubic metres and compares it with what the pump can actually supply. If the crop needs more water than the pump can deliver, the model limits benefits to the delivered amount rather than assuming a perfect irrigation outcome. That makes the result more conservative and more believable.

The final output is meant to support decisions, not replace field advice. You can use it to estimate annual diesel savings when replacing an engine pump, to explore how much additional revenue might come from better yields, and to see whether annual benefits remain strong enough to cover debt service. The year-by-year list is particularly useful when discussing DSCR with a lender, while the NPV figure helps compare solar irrigation with other uses of capital. In short, the planner brings financing and agronomy into one place so the economics of a solar pump can be discussed in plain language.

How to use

Start with the financing fields because they establish the amount that must be paid back. Enter the full solar pump package cost, including any controller, piping, mounting, or installation charges that will actually appear on the quote. If the farmer expects a grant, rebate, or results-based financing incentive, enter that amount separately. Then enter the farmer's down payment as a percentage of total cost, the annual interest rate, and the loan term in years. If the grant and down payment together cover the whole system, the planner will show zero financed principal and zero debt service, which is a valid scenario when a project is highly subsidised.

1. Fill in the financing structure using real quotations and lender terms.
2. Enter pump performance and farm water assumptions for the main irrigation season.
3. Add baseline yield, expected uplift, crop price, maintenance, and analysis horizon.
4. Read the summary first, then scan the year-by-year cash flow and export the CSV if you need to share the case.

Next, move to the agronomic fields. Pump capacity is entered in cubic metres per hour, while operating hours represent how long the solar system can realistically run on a typical irrigation day. The acreage field is labelled in hectares even though its id uses the older word acreage, so use land area in hectares. Crop water requirement is entered in millimetres per day. The calculator converts that depth of water into daily cubic metres across the selected farm area. Diesel cost should reflect the old cost per cubic metre of pumping water if the solar system is replacing a diesel pump. If the alternative was manual watering or a gravity-fed system, you can set diesel cost to zero and focus on crop revenue gains instead.

The final group controls how benefits are valued. Baseline yield is your current production per hectare without the improved irrigation setup. Yield uplift is the percentage improvement you expect from more reliable water, not the final yield itself. Crop price is the expected farmgate selling price per tonne. Maintenance is the annual amount you want to reserve for routine service, minor repairs, and upkeep. The analysis horizon should usually be at least as long as the loan term so you can see the entire repayment period. The discount rate affects NPV only; it does not change the simple cash flow. Once the inputs are set, the planner updates automatically. A strong result usually shows manageable debt service, a payback within the chosen horizon, and a DSCR above 1 during loan years.

Formula

The calculation follows the same sequence a credit analyst or farm manager would use on paper. First, the tool computes the farmer's down payment from the percentage entered. It subtracts both that down payment and any grant amount from the total package cost to get the financed principal. If a loan remains, the calculator amortises it using a standard monthly payment formula based on the interest rate and loan term. That produces an annual debt-service figure, which is the yearly repayment burden while the loan is active.

Water benefits are then estimated from the smaller of annual crop water demand and annual pump output. This matters because a crop cannot benefit from water that the pump never delivers, and a farm also cannot claim extra diesel savings on water it did not need in the first place. In words, the model is using the idea below before multiplying by the previous diesel pumping cost per cubic metre.

Revenue improvement comes from the crop side. Baseline yield per hectare is multiplied by hectares under irrigation to estimate total baseline production. The chosen uplift percentage is applied to that baseline to estimate additional tonnes produced, and that quantity is multiplied by the crop price. Annual net benefit is then calculated as avoided diesel cost plus additional crop revenue minus maintenance and minus debt service. Finally, NPV discounts those annual net benefits back to today's value. The page preserves the full discounted cash-flow expression below.

Here, D₀ is the down payment, S_y is avoided diesel cost in year y, R_y is the additional crop revenue, M_y is maintenance, L_y is annual loan service, r is the discount rate, and n is the analysis horizon. DSCR is shown separately during loan years and is calculated as annual operating benefit before debt service divided by annual debt service. A DSCR above 1 means the estimated annual benefit is enough to cover that year's repayments; a higher number gives more cushion.

Example

Suppose you use the default values already loaded into the form: a KES 320,000 solar pump package, a KES 60,000 grant, and a 15% down payment. The farmer pays KES 48,000 upfront, so the financed amount becomes KES 212,000. With a 12% annual interest rate over four years, annual debt service is roughly KES 67,000. On the water side, a 12 m³/hour pump running 6 hours per day delivers 72 m³/day. For 2 hectares with an 8 mm/day crop water requirement, total farm demand is about 160 m³/day, so the model correctly recognises that the pump does not fully meet theoretical demand. Over 220 irrigation days, useful water becomes 15,840 m³ per year, not the larger agronomic requirement.

If previous diesel pumping cost was KES 22 per cubic metre, that useful water implies about KES 348,480 in avoided pumping cost each year. Baseline production is 5.5 tonnes per hectare across 2 hectares, or 11 tonnes total. A 35% uplift adds 3.85 tonnes. At KES 24,000 per tonne, that is about KES 92,400 of extra crop revenue. After subtracting KES 18,000 of maintenance and the loan payment, annual net benefit during the loan years is roughly KES 355,600. Because the upfront outflow is only KES 48,000, simple payback arrives quickly in this illustrative case. If that seems optimistic for your farm, lower the diesel cost, reduce the yield uplift, shorten operating hours, or increase maintenance to test a more conservative scenario.

The table below is not part of the calculator's math, but it gives a sense of how different crop systems can shift outcomes. High-value horticulture often pays back faster because both diesel displacement and crop value are strong. Staple crops may still justify irrigation, but the margin for financing stress is usually smaller, so careful scenario testing matters more.

When reviewing your own result, use the summary list as the headline and the year-by-year performance list as the diagnostic tool. If the annual debt service looks high but payback still appears short, inspect DSCR for the repayment years. If NPV is positive but cumulative cash flow remains negative for several years, the project might still be economically attractive over the long term while feeling tight for a cash-constrained household. That distinction matters when planning how much working capital the farm needs during the first seasons after installation.

Limitations and assumptions

This planner intentionally stays simple enough to be usable in one sitting, which means it cannot capture every field reality. It assumes reliable access to a water source throughout the selected irrigation days. In practice, borehole yield, river flow, water-table depth, pump head, and pipe losses may reduce actual delivery. It also assumes that the stated operating hours are achievable with the available solar resource and system design. If shading, cloudy conditions, or undersized panels shorten daily runtime, actual useful water will be lower than shown.

The financial side is simplified too. The model treats annual benefits and annual maintenance as stable over time. It does not include inflation, tax, insurance, seasonal crop failure, controller replacement, battery replacement for hybrid systems, labour changes, or water-user permit fees. Crop prices can swing sharply across seasons, especially for vegetables sold into local spot markets. Yield uplift is likewise uncertain and depends on seed quality, fertiliser, pest pressure, agronomic management, and whether irrigation is paired with other good practices. A positive result should therefore be seen as an informed estimate rather than a guaranteed return.

There is also a planning limitation that matters for lenders: the calculator focuses on the irrigation investment, not the whole household budget. A farmer might have a strong project DSCR on paper but still struggle to make loan payments if school fees, medical expenses, or other business losses compete for cash. For that reason, the best use of this tool is as a conversation starter. Pair it with supplier quotes, field measurements, extension advice, and a broader household or cooperative cash budget before finalising any purchase. Used that way, the planner helps farmers and lenders compare scenarios transparently without pretending that one neat spreadsheet number can remove all risk.