Solar Irrigation System Calculator
Size a solar irrigation system for Australian horticulture and broadacre using ETo, Clean Energy Council PV data and CSIRO crop coefficients.
Solar Irrigation System Calculator
How to use this calculator
Enter eight values and the calculator returns daily water demand, hydraulic and electrical energy, the recommended PV array, the number of panels, pump operating power, and average flow during sun hours.
- Block area (hectares) — the irrigated area, typically the canopy area for orchards and vines, the centre-pivot circle for broadacre, the bed area for vegetables.
- Crop ETc (mm/day) — peak-season values: wine grapes (RDI managed) 4.5, table grapes 6.5, citrus 5.0, almonds 7.5, cotton 8.5, lucerne 8.0, vegetables 6.0–7.0. BoM ETo plus crop Kc from Agriculture Victoria, NSW DPI or DPIRD.
- Irrigation efficiency (%) — 90% drip, 85% microsprinkler, 80% centre pivot, 70% travelling gun, 60% furrow. Irrigation Australia certified evaluators measure distribution uniformity.
- Total dynamic head (m) — pumping water level plus pipe friction plus emitter pressure (drip 10–15 m, sprinkler 30–55 m).
- Peak sun hours/day — annual average. Typical Australian PSH (BoM): Mildura 5.5, Griffith 5.4, Renmark 5.3, Bundaberg 5.4, Geraldton 6.0, Alice Springs 6.4, Hobart 4.0, Sydney 4.5.
- Pump wire-to-water efficiency (%) — 45% default for a Lorentz PS2 or Grundfos SQFlex submersible; 50% for properly matched helical-rotor.
- System derate (%) — combined controller, wiring and soiling losses. 85% is a reasonable default; drop to 80% in dusty inland blocks.
- Panel wattage (W) — 400 W standard; 540 W bifacial in agricultural ground-mount.
How solar irrigation works in Australia
A solar irrigation system has the same components as a solar livestock pump — PV array, MPPT controller, DC pump — plus the irrigation network of filtration, mainlines, submains, laterals and emitters or sprinklers. Most Australian installations buffer with a 30,000–100,000 L poly tank or a small earth dam at elevated head, with the pump filling the tank during the day and gravity feed handling emitter pressure during the irrigation set.
Surface water abstractions need a water access licence in NSW, Victoria, Queensland and South Australia; bore allocations are managed by state water resources departments. Solar pumping does not change the licensing requirement but does shift the consumption profile — solar-direct systems pump roughly in line with crop ET because both peak in summer, which simplifies water budgeting.
The Clean Energy Council Approved Solar Retailer scheme covers PV components for solar pumping projects, and the Murray-Darling Basin Sustainable Diversion Limit Adjustment Mechanism has funded solar-direct conversions of diesel pumping under the Off-farm Efficiency Program.
The physics, derived first principles
Daily water demand from ETc and irrigation efficiency:
V_L_day = ETc_mm × Area_m² / efficiency_fraction
V_m3_day = V_L_day / 1000ETc in mm/day times area in m² gives litres per day directly (1 mm × 1 m² = 1 L).
Hydraulic energy to lift through TDH:
E_hydraulic_Wh = 1000 × 9.81 × V_m3 × H_m / 3600 ≈ V_m3 × H_m × 2.725Electrical input through pump and system losses:
E_electrical_Wh = E_hydraulic_Wh / (η_pump × η_system)
PV_Wp = E_electrical_Wh / PSHWorked example — one hectare table grapes, Sunraysia
- Area = 10,000 m², ETc = 6.5 mm/day, drip efficiency 85%
- V = 6.5 × 10,000 / 0.85 = 76,471 L/day = 76.47 m³
- TDH = 40 m (28 m bore pumping level + 4 m filtration + 8 m emitter pressure)
- E_hyd = 76.47 × 40 × 2.725 = 8,335 Wh/day
- Pump η 45%, system η 85%: E_elec = 8,335 / (0.45 × 0.85) = 21,790 Wh/day
- PSH 5.4: PV = 21,790 / 5.4 = 4,035 Wp → eleven 400 W panels (4,400 Wp, 9% headroom)
The CSIRO Sustainable Agriculture Flagship and CRC Irrigation Futures both recommend adding 25–40% PV oversizing to the worst-month calculation. The worked block sized to summer average needs an additional 25% to handle pre-dawn pumping demand and panel degradation over 25 years, taking the install to about 5,500 Wp.
Australian irrigation efficiency by method
| Method | Distribution efficiency | Pressure required |
|---|---|---|
| Subsurface drip | 88–95% | 10–14 m |
| Surface drip | 85–92% | 10–14 m |
| Microsprinkler | 80–88% | 14–21 m |
| Centre pivot | 80–90% | 30–55 m |
| Lateral move | 80–90% | 28–55 m |
| Travelling gun | 65–75% | 45–70 m |
| Furrow / flood | 50–70% | 5–15 m |
For solar pumping where PV cost scales with pump power, drip is the right answer for most permanent horticulture. Citrus, almond and stone fruit blocks are now nearly 100% drip across MIA, Sunraysia and Riverland. Broadacre crops in southern Queensland and northern NSW still run furrow or pivot, where solar pumping competes against diesel rather than drip.
CSIRO and DPIRD field study results
CSIRO Sustainable Agriculture Flagship and DPIRD tracked roughly 300 solar pumping installations on irrigated horticultural holdings across MIA, Sunraysia, Riverland and Sundown from 2017 to 2024:
- Median installed cost: A$8,500/ha for new-build drip; A$5,200/ha for retrofitting solar to existing diesel pump infrastructure.
- Median payback period versus diesel: 4.2 years in inland horticulture (high pump utilisation), 6.1 years in coastal districts.
- Ten-year retention: 91% of installations still in original operation, vs. project 75%.
- Most common failure mode: pump controller at 10–14 years, not the pump or panels.
The economics are strongest where solar replaces diesel pumping at A$1.80–2.20/L fuel cost or replaces grid pumping at irrigation-tariff peak rates.
Australian incentives and rebates
- Instant Asset Write-Off — Eligible primary producers can write off solar pumping equipment in the year of installation, with thresholds varying by federal budget cycle.
- Small Business Energy Incentive — 20% bonus deduction on energy-efficient plant including solar pumps (when active).
- NSW Energy Savings Scheme — Energy Saving Certificate revenue for qualifying solar pump installations.
- Victoria Solar for Business — A$3,500 rebate for small-business solar PV including water pumping systems.
- Murray-Darling Basin Sustainable Diversion Limit Adjustment Mechanism — funded solar-direct pumping conversions under the Off-farm Efficiency Program.
- State NRM grants — Local Land Services and CMAs (NSW, Vic, SA, Qld) often co-fund solar pumping when the project reduces diesel emissions or water consumption.
Common Australian-specific mistakes
- Sizing to ETo instead of ETc. Forgetting the crop coefficient under-sizes by 25% for citrus under regulated deficit, over-sizes by 30% for early-season lucerne.
- Using static water level for the bore. Bore draw-down across the Great Artesian Basin and Mallee aquifers averages 8–25 m under typical horticultural pumping. Use the pumping water level from the bore licence record or the drilling log.
- Designing to annual-average PSH. July PSH in Sunraysia is 3.6 vs. summer 7.0. Solar-direct systems are nominally for summer crops anyway, but lucerne, year-round vegetables and protected cropping need worst-month sizing.
- Ignoring filtration head. A media filter for solar drip adds 6–10 m of TDH at design flow; disc filters add 4–7 m. Bore water with carbonate hardness needs additional treatment, adding another 4–6 m.
Sources
- Bureau of Meteorology evapotranspiration data — daily ETo at reference stations
- Clean Energy Council solar pumping resources — Australian solar PV standards and installer scheme
- Agriculture Victoria irrigation efficiency — crop coefficients and distribution uniformity benchmarks
- Irrigation Australia — certified evaluator scheme and design standards
- CSIRO Sustainable Agriculture Flagship — long-term solar pumping performance studies
- FAO Irrigation and Drainage Paper 56 — reference ET methodology
- Lorentz Australia sizing manuals — solar pump curves