How to Size a Solar Water Pump System for Irrigation

How do you size a solar water pump for irrigation? Start by calculating the daily irrigation water requirement, convert that demand into the required pumping flow, calculate total dynamic head (TDH) including lift, irrigation pressure and pipe losses, and define the pump duty point. Then match that duty point to a verified pump performance curve before sizing the controller and PV array.

Correct solar water pump sizing for irrigation starts with the field’s hydraulic requirements, not with pump horsepower or a fixed number of solar panels. The selected pump must deliver the required flow at the required head while remaining compatible with the water source, irrigation network, controller and available solar resource.

For farms using drip irrigation, sprinklers, deep wells, reservoirs or storage tanks, poor sizing can result in weak pressure, insufficient daily water delivery, excessive pipe losses, unstable operation or unnecessary system cost.

Quick Solar Irrigation Pump Sizing Sequence

Crop & Field Area → Daily Water Demand → Irrigation Efficiency → Required Flow → Irrigation Zones → Water Source → Dynamic Water Level → TDH → Irrigation Pressure → Duty Point → Pump Curve → Source Yield → Pipe System → Storage Strategy → Controller → PV Array

Key principle: size the water system first. Size the solar power system second.

The 3 Numbers You Need Before Choosing a Pump

Required Value	What It Tells You
Daily water requirement	How much water the farm must receive during the design period.
Required pumping flow	How quickly the system must deliver that daily volume.
Total dynamic head (TDH)	The total hydraulic resistance the pump must overcome, including lift, irrigation pressure and friction losses.

Together, required flow + required TDH define the pump duty point. That operating point is much more useful for pump selection than horsepower, maximum head or maximum flow alone.

What Information Do You Need Before Sizing a Solar Irrigation Pump?

Project Data	Why It Matters
Crop type and growth stage	Helps determine irrigation water demand.
Irrigated area	Used to calculate total daily water volume.
Irrigation depth	Defines how much water is applied over the field.
Irrigation method	Changes required flow and operating pressure.
Water source	Determines pump type and lifting conditions.
Static and dynamic water levels	Important for groundwater and borehole systems.
Water-source yield	Limits the sustainable pumping rate.
Pipe length and internal diameter	Used to estimate friction losses.
Field elevation	Adds delivery head.
Required irrigation pressure	Adds pressure head for drip, sprinkler, filtration or fertigation equipment.
Available pumping hours	Used to convert daily water demand into required flow.
Local solar conditions	Affect daily pumping energy and PV-array design.

Based on our experience manufacturing solar pumps for agricultural and off-grid water applications, the most reliable pump selections begin with the actual daily water requirement, required flow and total dynamic head rather than field size or motor horsepower alone.

For a broader overview of the system itself, see our guide to the key components and working principles of solar water pumps.

Step 1: Calculate Daily Irrigation Water Demand

The first step is to determine how much water the crop needs during the design period.

Actual irrigation demand can depend on:

• Crop type and growth stage
• Climate and evapotranspiration
• Temperature, wind and humidity
• Effective rainfall
• Soil characteristics
• Irrigation schedule
• Field area

Convert Irrigation Depth Into Water Volume

A useful agricultural conversion is:

1 mm of irrigation over 1 hectare = 10 m³ of water

Therefore:

Daily Water Volume (m³/day) = Irrigation Depth (mm/day) × Field Area (ha) × 10

Example

Suppose a 2-hectare field has an example net irrigation requirement of 5 mm/day:

5 × 2 × 10 = 100 m³/day

The result is a net water requirement of approximately 100 m³/day.

Important: 5 mm/day is only an example. The actual design irrigation depth should come from crop, growth stage, climate, rainfall, soil and irrigation-planning data.

For more background on agricultural water planning, see our daily water requirements guide for livestock and irrigation.

Step 2: Account for Irrigation Efficiency

The crop’s net water requirement is not always the same as the amount of water that must be pumped. Losses can occur through evaporation, runoff, leakage and uneven distribution.

A simplified relationship is:

Gross Water Requirement = Net Water Requirement ÷ Irrigation Efficiency

Example

If the net requirement is 100 m³/day and the design assumes an example irrigation efficiency of 85%:

100 ÷ 0.85 ≈ 118 m³/day

The pump and water source would therefore need to support approximately 118 m³/day under this example.

Important: 85% is an example, not a universal efficiency value. Actual efficiency depends on the irrigation method, distribution uniformity, system condition and field management.

Step 3: Determine the Required Pumping Flow Rate

Once daily water volume is known, determine how quickly that water must be delivered.

A useful starting calculation is:

Required Average Flow = Daily Water Requirement ÷ Available Pumping Hours

Example

If the gross requirement is approximately 118 m³/day and the preliminary design assumes 7 effective pumping hours:

118 ÷ 7 ≈ 16.9 m³/h

The preliminary required flow is therefore approximately 17 m³/h.

Do not treat seven hours as a universal solar pumping period. Effective pumping time depends on location, season, solar irradiance, PV sizing, pump characteristics, controller behavior and whether water storage is used.

Step 4: Check Irrigation Zones Before Finalizing Flow

Large farms are often divided into irrigation zones rather than operating every sprinkler or drip line at the same time.

Zoning can reduce the instantaneous flow requirement while still allowing the total daily water target to be delivered over the available operating period.

For example, a field may be divided into four zones and irrigated sequentially. In that case, the pump should be checked against the flow and pressure required by the active zone, while the complete schedule must still deliver the required daily water volume.

This distinction is especially important for drip irrigation and sprinkler systems because instantaneous zone demand can differ substantially from whole-field daily demand.

Step 5: Identify the Water Source and Choose the Pump Type

The water source affects both the pump type and the required hydraulic head.

Water Source	Typical Pump Approach	Main Selection Data
Deep well or borehole	Solar submersible pump	Dynamic water level, borehole diameter, required flow, TDH and well yield
Pond, canal, river or reservoir	Surface pump or submersible pump depending on installation	Water-level variation, suction conditions, delivery head and irrigation pressure
Existing storage tank	Surface or submersible transfer/pressure pump depending on layout	Tank elevation, required flow, downstream pressure and pipe losses
Farm requiring backup operation	DC solar or AC/DC hybrid configuration where supported	Operating schedule, reliability requirement and available backup power

Deep Well or Borehole

For groundwater systems, collect:

• Total borehole depth
• Static water level
• Dynamic water level while pumping
• Borehole diameter
• Tested or estimated sustainable well yield

Well depth is not the same as pump head. A 100-meter-deep borehole does not automatically require 100 meters of lifting head. The dynamic water level during pumping is generally more relevant to the actual vertical lift.

For more detail, see our solar submersible pump guide for remote wells and boreholes.

Pond, River, Canal or Reservoir

For surface-water sources, determine the vertical difference between the source water level and delivery point, along with seasonal water-level variation and suction conditions if a surface pump is used.

Product Selection Note

For irrigation projects, Sunbeam Pump can configure solar submersible and surface pumping solutions with direct-solar or AC/DC hybrid control options depending on the application. The pump model should still be selected from the required flow + TDH duty point, not from horsepower alone.

Step 6: Calculate Total Dynamic Head (TDH)

Total Dynamic Head (TDH) is the total hydraulic head the pump must overcome while delivering the required flow.

For many irrigation systems:

TDH = Water Lift + Delivery Elevation + Required Pressure Head + Friction Losses

For a deep-well irrigation system, this can be expressed more specifically as:

TDH = Dynamic Water Level Lift + Field Elevation + Irrigation Pressure Head + Pipe/Equipment Losses

TDH Example

• Dynamic water level: 35 m below ground
• Field elevation above wellhead: 8 m
• Required irrigation pressure head: 25 m
• Estimated pipe, filter and fitting losses: 7 m

TDH = 35 + 8 + 25 + 7 = 75 m

The pump should therefore be evaluated at the required irrigation flow and approximately 75 m TDH.

Common mistake: do not use total well depth as TDH unless the hydraulic conditions actually require it. TDH must represent the real operating system.

Step 7: Include Irrigation Pressure Requirements

An irrigation pump does more than move water from one elevation to another. Drip and sprinkler systems often need a minimum pressure at the irrigation inlet or emitters.

Pressure requirements may come from:

• Sprinkler nozzles
• Drip emitters
• Pressure regulators
• Filters
• Fertigation equipment
• Long laterals and submains

A useful conversion is:

1 bar ≈ 10.2 m of water head

For example, an irrigation inlet requiring 2.5 bar corresponds to approximately 25.5 m of pressure head before other system losses are added.

The actual operating pressure should come from irrigation-equipment design or manufacturer specifications. Do not assume one universal pressure for every drip or sprinkler system.

Step 8: Determine the Pump Duty Point

Once the required flow and TDH are known, combine them into the pump’s required duty point.

Duty Point = Required Flow at Required Head

Example

• Required flow: approximately 17 m³/h
• Required TDH: approximately 75 m

The required operating point is therefore approximately:

17 m³/h @ 75 m TDH

This is the point that should be taken to the pump performance curve.

Why this matters: a pump advertised with a maximum head of 100 m may not deliver 17 m³/h at 75 m. Maximum head, maximum flow and rated horsepower do not describe the complete operating point.

Step 9: Select the Pump Using the Performance Curve

Compare the required duty point with the manufacturer’s verified pump curve.

Do not select an irrigation pump based only on:

• Maximum head
• Maximum flow
• Motor horsepower

Maximum head normally occurs near very low flow, while maximum flow occurs at much lower head. These values should not be treated as if they occur simultaneously.

The correct question is:

Can this pump deliver the required flow at the calculated TDH?

The selected duty point should fall within an appropriate operating region of the actual manufacturer performance curve rather than close to an extreme end wherever practical.

In a variable-speed solar pumping system, the actual operating point can move during the day as available solar power and pump speed change. The design duty point is still the key reference for model selection and system verification.

Step 10: Verify Water-Source Yield

A pump cannot sustainably deliver more water than the source can provide.

For a borehole, compare required pump flow with:

• Tested well yield
• Dynamic water level
• Drawdown
• Recovery rate

If a pump is capable of 17 m³/h but the well can sustainably supply only 10 m³/h, the system design must be adjusted. Possible solutions may include lower pumping flow, longer pumping hours, additional storage or a revised irrigation schedule.

For surface-water sources, also consider seasonal water-level changes and available water volume.

Step 11: Check Pipe Diameter and Friction Loss

Pipe friction is a common source of hidden head loss in agricultural irrigation systems.

Friction loss depends on:

• Flow rate
• Internal pipe diameter
• Pipe length
• Pipe material and roughness
• Elbows and bends
• Valves
• Filters
• Other fittings

In general, higher flow through a long or undersized pipe increases friction loss, which raises TDH and can reduce actual field pressure.

A larger pipe may reduce hydraulic losses, but pipe cost, acceptable water velocity and installation constraints should also be considered.

Step 12: Decide Between Direct Solar Irrigation and Water Storage

Direct Solar Irrigation

The solar pump supplies the irrigation network directly while sufficient solar power is available. The pump must provide the required flow and irrigation pressure while the active irrigation zone is operating.

Solar Pump Plus Water Storage

The pump fills a storage tank or reservoir during available solar hours, and irrigation occurs later using gravity or a secondary pressure system.

The main advantage is that water storage can separate pumping time from irrigation time. This can help when crops need irrigation early in the morning, late in the day or according to a schedule that does not match peak solar availability.

Water storage is not the same as electrical battery storage. For many agricultural applications, storing pumped water can be a practical way to shift when that water is used without storing electricity.

Step 13: Match the Solar Pump Controller

After the pump has been selected hydraulically, check that the controller is compatible with the pump and PV array.

Important parameters include:

• Pump rated power
• Pump rated voltage
• Motor type
• Controller input voltage range
• Controller maximum input voltage
• Operating current
• PV-array voltage and power limits

Depending on the controller model, functions may include MPPT, dry-run or water-shortage protection, tank-full stop or water-level control, over-current protection, over-voltage protection, under-voltage protection and phase-related protection where applicable.

For projects that require backup operation, an AC/DC hybrid controller can be considered where supported by the pump and system design.

For general system architecture, see our solar water pump components and working-principles guide.

Step 14: Size the PV Array for the Selected Pump

The solar array should be designed only after the pump and controller requirements are known.

PV sizing should consider:

• Pump rated power
• Pump operating voltage
• Controller requirements
• PV module Vmp
• PV module Voc
• Cold- and hot-temperature effects on PV voltage
• Local irradiance
• Seasonal solar variation
• Required daily water production
• Expected system losses

There is no universal number of solar panels for an irrigation pump.

The same pump can require different panel quantities when different PV modules are used, and systems in different climates may require different electrical configurations and operating strategies.

Design for the Critical Irrigation Period

Do not size the system only around average annual solar conditions.

The critical design period is the period that creates the most difficult combination of:

• High crop water demand
• Available solar energy
• Water-source capacity
• Required daily pumping time

The key design question is:

Can the system deliver enough water during the most demanding irrigation period?

For more background on solar pump performance in reduced sunlight, see our guide to solar water pump performance on cloudy days.

Step 15: Consider Backup Power Where Required

Some farms cannot rely entirely on daytime solar pumping.

Where supported by the pump and controller, an AC/DC hybrid system may allow solar power to act as the primary energy source while grid power or a generator provides backup during prolonged low-solar conditions or unusually high irrigation demand.

The need for backup should depend on the irrigation schedule, crop sensitivity, available water storage and reliability requirements rather than being assumed for every project.

Complete Solar Irrigation Pump Sizing Example

Consider the following preliminary project:

Design Item	Example Value
Irrigated area	2 ha
Net irrigation depth	5 mm/day
Example irrigation efficiency	85%
Example effective pumping time	7 h/day
Dynamic water level	35 m
Field elevation	8 m
Required irrigation pressure head	25 m
Estimated friction/equipment losses	7 m

1. Calculate Net Water Demand

5 × 2 × 10 = 100 m³/day

2. Calculate Gross Water Requirement

100 ÷ 0.85 ≈ 118 m³/day

3. Calculate Required Flow

118 ÷ 7 ≈ 16.9 m³/h

Preliminary required flow: approximately 17 m³/h.

4. Calculate TDH

35 + 8 + 25 + 7 = 75 m TDH

5. Define the Duty Point

Approximately 17 m³/h @ 75 m TDH

6. Verify Source Yield

Confirm that the well or other source can sustainably provide the required pumping rate.

7. Match the Pump Curve

Select a pump whose verified performance curve can provide approximately 17 m³/h at 75 m TDH within a suitable operating range.

8. Check the Pipeline

Confirm pipe diameter, pipe length, filter losses, valve losses and other fittings so the estimated friction allowance reflects the actual system.

9. Decide Direct Irrigation or Storage

Determine whether the pump will feed the irrigation network directly or fill storage for later irrigation.

10. Match the Controller and PV Array

Use the selected pump’s electrical specifications, controller limits, PV-module data and critical-period solar resource to complete the electrical design.

Important: this example demonstrates the sizing process. The values 5 mm/day, 85% efficiency, 7 pumping hours and 25 m pressure head are examples only and should not be treated as universal design values.

Common Solar Irrigation Pump Sizing Mistakes

Selecting by Farm Area Alone

Field area does not define crop water demand, irrigation pressure, pumping hours or TDH.

Selecting by Horsepower Alone

Horsepower does not show the flow a pump will deliver at the required head.

Using Well Depth as Pump Head

Total borehole depth and dynamic water level are different. The hydraulic lift should be based on actual operating conditions.

Using Maximum Flow and Maximum Head Together

These values normally occur at different points on the performance curve.

Ignoring Irrigation Efficiency

Net crop water demand and gross pumped water demand can be different.

Ignoring Irrigation Pressure

A pump may move enough water but still fail to provide the pressure required by sprinklers, regulators or filters.

Ignoring Pipe Friction

Long or undersized pipes can add substantial TDH and reduce field pressure.

Ignoring Water-Source Yield

A larger pump cannot create additional water if the borehole or source cannot sustain the required flow.

Choosing Solar Panels Before Selecting the Pump

The hydraulic duty point should be defined before the PV array is finalized.

Designing Only for Ideal Solar Conditions

The system should be checked against the project’s critical irrigation period, not only the best solar month.

Solar Irrigation Pump Sizing Checklist

• Country and project location
• Crop type and growth stage
• Irrigated area
• Required irrigation depth or daily water demand
• Irrigation method
• Number of irrigation zones
• Required zone flow
• Required irrigation pressure
• Water source
• Total well depth where applicable
• Static water level
• Dynamic water level
• Well or source yield
• Delivery elevation
• Pipe length
• Pipe internal diameter
• Pipe material
• Filters, valves and fittings
• Required daily pumping period
• Direct irrigation or storage strategy
• Available PV module specifications
• Grid or generator backup availability

Providing these values makes it possible to evaluate the real duty point rather than relying on field area, horsepower or maximum pump ratings alone.

Frequently Asked Questions About Solar Water Pump Sizing for Irrigation

How do I size a solar water pump for irrigation?

Calculate daily irrigation water demand, determine the required pumping flow, calculate TDH including irrigation pressure and friction losses, and combine flow and TDH into a duty point. Then match that duty point to a verified pump curve before sizing the controller and solar array.

How much water does 1 mm of irrigation equal?

One millimeter of water applied over one hectare equals approximately 10 cubic meters of water.

How do I calculate irrigation pump flow rate?

A useful starting point is daily water requirement divided by realistic available pumping hours. Then verify the result against irrigation-zone flow requirements and water-source capacity.

What is TDH in an irrigation system?

Total dynamic head is the total hydraulic head the pump must overcome. It can include water lift, delivery elevation, required irrigation pressure and friction losses through pipes and equipment.

Is well depth the same as pump head?

No. Total well depth and dynamic water level are different. In a borehole system, dynamic water level is generally more relevant to actual vertical lifting head.

Does drip irrigation require pressure?

Yes. Required pressure depends on the emitters, filters, regulators and complete irrigation-system design. There is no single universal pressure for every drip system.

How does sprinkler pressure affect solar pump sizing?

Required sprinkler pressure becomes part of TDH. A higher operating pressure therefore increases the head the pump must deliver at the required flow.

Can a solar submersible pump be used for irrigation?

Yes. Solar submersible pumps are commonly used for irrigation from wells and boreholes when they are correctly matched to required flow, TDH, borehole diameter and sustainable well yield.

Can a solar water pump irrigate directly without batteries?

Yes, depending on the pump, controller, solar resource and irrigation design. Some systems irrigate directly during solar hours, while others pump water into storage for later use.

Is water storage better than batteries for solar irrigation?

Water storage can be a practical way to separate daytime pumping from irrigation timing without storing electricity. The best solution still depends on required pressure, tank elevation, irrigation schedule and project reliability needs.

How many solar panels are needed for an irrigation pump?

There is no universal panel count. The required array depends on pump power and voltage, controller limits, PV module Vmp and Voc, temperature, solar irradiance and required daily water production.

What information should I send a solar pump supplier?

Provide crop and field data, daily water requirement, irrigation method, required flow and pressure, dynamic water level, source yield, delivery elevation, pipe length and diameter, and available solar conditions.