Solar Irrigation Pump Sizer
Calculate total dynamic head, pumping rate, pump horsepower and the solar panel wattage needed for your daily irrigation water.
Enter your details
Enter how much water you need per day, the depth of the water and how high you lift it, and your area's sunshine hours. The calculator works out the total head, the pump size in HP and the solar array wattage – the numbers to check any solar pump quotation, including under PM-KUSUM.
About the Solar Irrigation Pump Sizer
A solar pump has no fuel bill, but it only pumps while the sun shines, so it must be sized to lift your whole day's water in a few hours. Too small and the crop goes short; too large and you pay for panels you don't need.
Three numbers decide the size:
- Total dynamic head (TDH) – the height from the water level in the well up to the delivery point, plus an allowance for friction in the pipes. Every extra metre of head needs more power.
- Daily water – divided by the peak sun hours, this gives the pumping rate the pump must deliver.
- Efficiencies – of the pump and motor, and of the solar array in real conditions.
The calculator turns these into pump horsepower and solar array wattage. Under PM-KUSUM and state schemes, pumps come in standard ratings (such as 3, 5, 7.5 and 10 HP) with a matching array size fixed by MNRE specifications, typically around 0.9–1 kWp per HP. Pick the standard pump at or just above the result, and check that the supplier's head–discharge curve delivers your flow at your TDH.
How to use the Solar Irrigation Pump Sizer
- 1 Enter the water you need per day.
- 2 Enter the pumping water level below ground and the height to which you deliver water.
- 3 Keep 10% friction for a short, well-sized pipe; raise it for long or thin pipes.
- 4 Enter your peak sun hours and press Size my pump.
The formula we use
TDH (m) = (Water level depth + Delivery height) × (1 + Friction %)
Flow (m³/h) = Daily water (m³) ÷ Peak sun hours
Water power (kW) = Flow (m³/h) × TDH (m) × 9.81 ÷ 3,600
Pump power (kW) = Water power ÷ Pump efficiency; HP = kW ÷ 0.746
Solar array (Wp) = Pump power (kW) ÷ Array performance × 1,000Worked example
You need 60,000 litres a day from a bore with the water at 30 m, delivering 5 m above ground, with 10% friction, 5.5 sun hours, 45% pump efficiency and 80% array performance.
- TDH = (30 + 5) × 1.1 = 38.5 m.
- Flow = 60 m³ ÷ 5.5 h = 10.91 m³/h.
- Water power = 10.91 × 38.5 × 9.81 ÷ 3,600 = 1.14 kW.
- Pump power = 1.14 ÷ 0.45 = 2.54 kW = 3.41 HP – choose a 5 HP standard pump, or a 3 HP pump if you can accept slightly less water.
- Solar array = 2.54 ÷ 0.8 = 3,178 Wp, about 6 panels of 540 W.
Things to keep in mind
- Water level drops in summer. Size for the lowest pumping water level of the season, when you need the most water.
- Check the pump curve. A pump's flow falls as head rises; make sure the chosen pump gives your flow at your TDH.
- Store water. A small tank or farm pond lets a solar pump fill up in the day for drip or evening irrigation.
- Keep panels clean – dust can cut output by 10–20% in dry areas.
Frequently asked questions
What size solar pump do I need for one acre?
It depends on the crop's water need and the depth of water. For 50 mm of water every 5 days (about 40,000 litres a day) from 30 m, the answer is around 2–3 HP; enter your own numbers above.
What is total dynamic head?
The total height the pump must lift water – from the water level to the delivery point – plus the extra pressure needed to push water through pipes and fittings.
How many solar panels for a 5 HP pump?
Scheme specifications usually pair a 5 HP pump with an array of about 4.8 kWp, which is 9 panels of 540 W.
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