Solar Water Pump for Agriculture: Complete Irrigation Guide

The short answer: to size a solar pump for agriculture, you need two numbers: (1) how much water your crops need per day, and (2) the total dynamic head (TDH) at the required flow. The daily need divided by sun hours gives you the required flow rate. Then match those to a pump curve. This guide gives you the numbers for common crops and irrigation methods.

Water needs by irrigation method

Drip irrigation uses the least water and is the best match for solar pumps — it needs lower flow rates, which means smaller pumps and fewer solar panels.

For protected crops, the solar greenhouse irrigation guide works through demand, micro-sprinkler pressure and tank control for that setting.

Water needs by crop

Treat these as planning numbers, not gospel — local weather, soil, and variety shift them by 20-30%.

For fruit trees, refine the area-based estimate with the tree counts, seasonal demand and layout in the solar orchard irrigation guide.

How to calculate your pump size

Step 1: Total daily water need = hectares × crop water need per hectare

• Example: 3 hectares of tomatoes at 35 m³/ha/day = 105 m³/day

Step 2: Required flow rate = daily water ÷ irrigation hours

• If you irrigate 8 hours/day: 105 ÷ 8 = 13 m³/h
• If using solar (6h sun): 105 ÷ 6 = 17.5 m³/h
• Use a water tank to extend irrigation beyond sun hours — fill the tank during sunlight, irrigate from the tank during evening/night

Step 3: Calculate total dynamic head (TDH)

• TDH = static water-level depth below the wellhead + drawdown at the design flow + delivery elevation above the wellhead + pipe/fitting/filter losses + required outlet pressure head (all in metres). Borehole depth is an installation constraint, not the lift; static water level + drawdown gives the pumping water-level depth.
• See head calculation guide

Step 4: Match to a pump

• Select from a verified pump curve at the required flow and TDH, and use the efficiency at that point. At 25 m³/h and 70m TDH, hydraulic power is 1,000 × 9.81 × (25 ÷ 3,600) × 70 ≈ 4.77kW. A 4-5 HP pump is insufficient even before losses; shaft power = 4.77 ÷ pump efficiency, with motor/controller losses added for electrical sizing.
• Use our sizing tool for instant matching

Note: “irrigation hours” in Step 2 can differ from “sun hours” — if you pump 6 hours and irrigate 8-10 from the tank, you size the pump from the sun hours but run the field on your own schedule.

Scheduling irrigation around the sun

Solar power and good irrigation practice line up well — once there’s a tank in the system. Night irrigation needs stored water with sufficient delivery pressure or a compatible night-time power supply; a timer only schedules that available water or power and adds no energy:

• Pump during peak sun (roughly 10:00-16:00), when panels produce the most.
• Irrigate early morning and late afternoon. This cuts evaporation and avoids leaf burn on hot crops.
• Let the tank bridge the gap. A typical day: the pump fills the tank midday while drip lines run 06:00-09:00 and 17:00-20:00 from it.
• Cloudy days: with 1.5-2 days of tank storage, irrigation runs from stored water while the pump takes whatever sun it can get.

Filtration: drip emitters are picky

The most common cause of a dead drip system isn’t the pump — it’s clogged emitters. Sand, silt, and algae that pass the pump block drip lines within weeks:

• Install a screen or disc filter (120-mesh or finer for most well water) on the mainline before the drip laterals.
• For sandy wells, add a sand separator (hydrocyclone) upstream of the filter.
• Monitor the pressure gauge across the filter — when pressure drop grows, it’s cleaning time.
• Size the filter for the pump’s flow, not the field’s average use.
• Add the filter’s 0.2-0.5 bar loss to your TDH — a pump sized without it will under-deliver at the emitters.

Soil and crop considerations

Your soil type changes the schedule even when the crop is the same:

• Sandy soil drains fast — smaller, more frequent irrigations keep the root zone wet.
• Clay soil holds water — bigger, less frequent irrigations and a larger tank.
• Crop stage matters: seedlings need light, frequent watering; mature crops need more volume less often. Size the tank for the seedling stage and the pump for the peak stage.
• Hot, dry, windy weather pushes evaporation up — irrigate earlier in the morning.

Example configurations

Well depths below describe installation conditions, not TDH. Pump powers, panel counts and budgets are preliminary examples; verify each against the actual flow/TDH curve, efficiencies and controller limits, then revise the array and budget.

Small farm: 1-2 hectares, drip irrigation

• Water need: 30-60 m³/day
• Typical well: 30-60m
• Pump: 1-2 HP (750W-1500W), DC submersible
• Solar panels: 4-8 × 550W
• Budget: $1,500-3,000 (pump + controller + panels)

Medium farm: 3-5 hectares, drip irrigation

• Water need: 90-200 m³/day
• Typical well: 50-100m
• Pump: AC/DC submersible selected by the actual duty curve and efficiency; 3-5 HP (2200W-3700W) is only a lower-duty example and cannot provide 25 m³/h at 70m TDH.
• Solar panels: 12-20 × 550W
• Budget: $5,000-12,000

Large farm: 10+ hectares, mixed irrigation

• Water need: 300+ m³/day
• Typical well: 80-150m
• Pump: 10-30 HP (7500W-22000W), AC/DC high-power
• Solar panels: 30-80 × 550W
• Budget: $15,000-50,000+

For a large field served by a pivot, work through center pivot pump sizing before using a general farm configuration.

Water tank strategy for solar irrigation

A water tank is your “battery” — it stores water pumped during sunlight for use anytime. This is cheaper and more reliable than battery storage for the solar panels.

Tank sizing rule: 1.5-2× your daily water need

• If you need 100 m³/day, use a 150-200 m³ tank
• This gives you 1-2 days of buffer for cloudy weather

Benefits:

• Pump runs at optimal efficiency during peak sun
• Irrigation happens at consistent pressure from the tank
• Cloudy days don’t stop irrigation
• Smaller pump can serve larger area (fills tank slowly, irrigates fast)

For a full comparison of storage options, see my battery vs tank guide.

Regional recommendations

For paddy fields, follow the solar rice paddy irrigation guide to account for land preparation, seepage and the irrigation schedule.

Ready to size your irrigation pump? Use the sizing tool with your calculated TDH and daily water need; provide borehole depth separately for installation. For complex multi-hectare projects, message me on WhatsApp — I’ll help design the complete system.