Guide

Solar for irrigation in NZ: pivots, pump sheds and what solar really saves

Michael Wilkins · Updated 3 October 2026 · 5 min read

The short answer

Grid-tied solar on a pump's connection saves the energy and the per-kWh lines charge, about 13 to 18 cents a kWh in our model, because Canterbury networks charge irrigation mostly for pump capacity. It pays when the pump runs in daylight: on our 100 ha pivot a 33 kW array pays back in 8 to 15.5 years that way, and 12 to 20 years with pumping spread across day and night. Solar stock-water pumps are a different, much smaller product.

Two different things called solar irrigation

Search for solar irrigation and most of what comes back is garden drip kits and standalone solar pumps. Those run off their own panels with no grid connection, and they suit troughs, tanks and small lifts: Perkinz quotes more than 100,000 litres a day in summer from its kits. A centre pivot works at another scale. Our 100 ha example is designed to apply 5 mm a day, which is 5,000 cubic metres. This guide is about the other kind of solar irrigation: a grid-tied array on the pump's own connection, running the pump while the sun shines, with the grid supplying the rest.

What a pivot uses

Pumping energy is physics. Lifting a megalitre of water one metre takes 2.7 kWh at the water, and the pump and motor lose the rest. So the head, meaning the lift from the water plus the pressure the pivot needs, sets the power bill more than anything else.

Water source	Total head	kWh per megalitre	kWh per mm per hectare	Pump size	A season's pumping
Pond, river or unpressurised scheme water	40 m	168	1.7	38 kW	67 MWh
Shallow bore, about 30 m lift	70 m	293	2.9	67 kW	117 MWh
Deep bore, about 80 m lift	120 m	503	5.0	114 kW	201 MWh

Energy at the meter for a 100 ha pivot applying 400 mm a season, designed for 5 mm a day over 22 hours, with pump and motor together 65 percent efficient. Total head is the lift plus the pressure the pivot needs; your own pump test sets the real figure.

Seasons vary more than pumps do: Lincoln University's dairy farm applied between 132 and 426 mm a season in the three seasons to 2024/25. For scale, EA Networks forecasts its 1,627 irrigation connections will use 192,340 MWh in 2026/27, about 118 MWh each, close to our shallow-bore example.

What solar saves on an irrigation connection

An irrigation connection is billed differently from a shed or a factory. Most of the lines charge is for pump capacity, set from the motors' ratings: EA Networks charges $0.4856 per kW a day all year, Orion $0.7005 per kW a day from 1 October to 31 March and MainPower $0.32756 a day per kW connected. Solar on the same connection does not change that capacity. It saves only the energy and the per-kWh lines charge: on EA Networks, an average demand charge on metered energy, worth 1.2 cents a kWh; on Orion, time-of-use charges from 1.4 cents at weekends to 8.0 cents in the weekday peak; on MainPower, a flat 3.0 cents a kWh.

Add energy on a fixed-price contract and solar avoids about 13 to 18 cents a kWh on an irrigation connection in our model, not the 20.4 to 25.5 cents we use for a general business. Ruralco reported Ashburton irrigators' contract energy rising from 8 to 9 cents a kWh to 12 to 13 cents by 2023. Irrigation connections must also stay dedicated, with no house or shed on the same supply (Orion requires it for pumps over 20 kW, EA Networks for every irrigation connection), so a dairy shed's array cannot run the pivot.

Daylight pumping decides the payback

Pumping peaks in the sunny months, which is why irrigation looks like a natural match for solar. Hour by hour it is not: Orion's irrigation customers use power across the week in almost the same shares as the hours themselves, so pumps run at night about as much as by day. Run that way, our 100 ha pivot uses about 27 percent of an array's output, a little more in practice because dry, sunny spells are when pumps run flat out. Move the pumping into daylight, as far as the system's capacity allows, and it uses about 78 percent.

Array	Output a year	Used by the pump: day and night / daylight	Pumping covered, daylight	Payback, day and night	Payback, daylight
17 kW	22 MWh	27 percent / 81 percent	15 percent	12 to 20 years	8 to 15.5 years
33 kW	43 MWh	27 percent / 78 percent	29 percent	12 to 20 years	8 to 15.5 years
50 kW	66 MWh	27 percent / 75 percent	42 percent	11.5 to 18.5 years	8 to 14.5 years
67 kW	88 MWh	27 percent / 72 percent	54 percent	10.5 to 17 years	7.5 to 13.5 years

Our 100 ha pivot on a 70 m head (a 67 kW pump) in Canterbury, with arrays from a quarter of the pump's power to all of it. Solar the pump uses is valued at 13 to 18 cents a kWh, the energy and per-kWh lines charge an irrigation connection avoids; exports at 8 cents. Payback after the Investment Boost tax cash, NZ$ ex GST.

Keep the array at or below the pump's power, so a running pump uses all of it. Beyond that, the payback depends on how much pumping you can move: a storage pond, a scheduler that starts the pump in the morning or a system with spare daily capacity all help. Pumping at night on cheap rates pulls the other way.

Month by month the shape is plain. From May to August the pump is idle and the array exports, and in the peak months a pump run day and night catches only part of what the panels make.

Month	Water	Pumping	Solar	Used, day and night	Used, daylight
January	84 mm	24.7	5.4	2.7	5.4
February	64 mm	18.8	4.5	1.9	4.5
March	40 mm	11.7	3.9	0.9	3.9
April	12 mm	3.5	3.0	0.2	3.0
May	0 mm	0.0	2.2	0.0	0.0
June	0 mm	0.0	1.7	0.0	0.0
July	0 mm	0.0	1.9	0.0	0.0
August	0 mm	0.0	2.6	0.0	0.0
September	8 mm	2.3	3.2	0.2	2.3
October	40 mm	11.7	4.3	1.0	4.3
November	64 mm	18.8	5.0	1.9	5.0
December	88 mm	25.8	5.4	2.8	5.4

Our 100 ha pivot with a 33 kW array in Canterbury, in MWh. Water follows a season from September to April that peaks in December and January; solar follows the typical South Island monthly shape. Months with no pumping export everything.

A Canterbury example

The Eiffelton Community Group Irrigation Scheme in Mid Canterbury added a 44 kW grid-tied array to a 50 kW groundwater pump for the 2021/22 season, with funding from MPI's Sustainable Food and Fibre Futures fund. Its business case modelled irrigation-only paybacks of 8.6 to 10.1 years for arrays of 22 to 88 kW in an average year, for a system designed and run to make the most of the sun, in line with the daylight column above. The trial season itself was wet, which cut pumping. A cited industry reference, not our project.

How we size it

We start from your pump: its power, head and hours, and twelve months of half-hourly data from the irrigation connection. The model above then runs on your numbers and your network's actual charges, and we tell you whether solar pays at your pumping pattern and what moving pumping into daylight would be worth. That is what the feasibility study provides.

The Canterbury figures are on our Canterbury irrigation page, and the other farm loads, with costs by size and rural finance, are in farm solar.

Your numbers

Run your own numbers

Conservative assumptions, fully disclosed, no contact details needed.

Your farm or business

What kind of operation?Region

Monthly power spend (ex GST)

When do you use power?Cooling, pumping or processing through the sunny hours.

Your indicative numbers

Conservative, ex GST, modelled not promised

Measure

Power used: 188,235 kWh a year; Your spend at 25.5c a kWh ex GST, the national commercial average.
Power bill: $48,000 a year

Design

System: 78 kW; Sized to your daytime load.
Generates: 102,180 kWh a year
Used on site: 75%; The rest exports at 8c a kWh.
Installed cost: $119,006 to $160,011; Confirmed with certified installers.

Finance

Investment Boost, year one: about $7,812; A 20% immediate tax deduction, worth this in cash at the 28% company rate. Not a discount.
ASB Smart Solar Loan: $2,325 a month; 0% for 5 years. Reverts to a floating business rate after five years. Terms checked against asb.co.nz on 8 October 2026. ASB may change or withdraw the offer; the calculator only shows it while it matches.
Estimated saving: $1,160 a month; Mid estimate, set against the repayment while the loan runs.

Outcome

Saving: $12,006 to $15,838 a year
Payback: 7 to 12.5 years; Net of the Investment Boost benefit.
Emissions avoided: 5.7 t CO₂e a year
Asset life: 25+ years; Panels keep producing long after payback.

How this is modelled (assumptions v2026-10-v7)

Power valued at $0.13 to $0.18/kWh ex GST (an irrigation connection pays mostly per kW of pump capacity, which solar cannot cut, so solar avoids only the energy and the per-kWh lines charge).
The pump uses 75 percent of the output when pumping is moved into daylight, 25 percent when it runs evenly across day and night; the irrigation connection carries no other load, so the rest exports.
Export credited at $0.08/kWh, the conservative end of current buy-back rates.
Installed cost interpolated from 30 kW ($1,800 to $2,600/kW) down to 500 kW ($1,100 to $1,500/kW), 2025/26 working ranges.
Canterbury yield modelled at 1310 kWh per kW per year.
Self-consumption capped by your daytime usage profile and held below typical vendor claims; sizing targets 90 percent of daytime load.
Investment Boost stated as the year-one cash value of the 20 percent immediate deduction at the 28 percent company rate. It is a tax timing benefit, not a discount.
No power price escalation and no panel degradation in simple payback; omitting escalation outweighs degradation, so the net effect is conservative.

Indicative only; not financial or tax advice. The feasibility study models your site from twelve months of actual bills.

Next step

Get these numbers checked properly

The real model is built from twelve months of your bills. Send your details and we will do it for you; we reply within one working day, no obligation.

Straight answers

The questions we get asked

Is solar worth it for irrigation?

It can be, if the pump runs in daylight. Pumping peaks in the sunny months, but most irrigators run pumps evenly across day and night, and an irrigation connection carries no other load. In our 100 ha pivot example a 33 kW array pays back in 12 to 20 years run that way, and 8 to 15.5 years with pumping moved into daylight. The deciding question is how much of your pumping you can shift.

How much does a solar irrigation system cost?

A grid-tied array for a pivot or pump shed is priced like any commercial system: about $59,000 to $85,000 installed for 33 kW and $140,000 to $180,000 for 100 kW in 2026, ex GST, before the Investment Boost deduction. Standalone solar pump kits for stock water are a different product; one New Zealand retailer lists turnkey kits from about $4,400 to $45,000.

Can solar power an irrigation pump directly?

Not a pivot pump: it is too large and runs too many hours for panels alone. Solar on a pivot is grid-tied. The array feeds the pump's own connection, so generation runs the pump whenever both are going and the grid supplies the rest. Direct-drive solar pumps suit small lifts and stock water away from the grid.

Does solar cut irrigation lines charges?

Only the per-kWh part. Irrigation connections pay mostly for pump capacity: EA Networks charges $0.4856 per kW a day all year and Orion $0.7005 per kW a day from 1 October to 31 March, and solar does not change either. It cuts the energy and the per-kWh lines charge, which we value at 13 to 18 cents a kWh, against 20.4 to 25.5 cents on a general business connection.

What happens outside the irrigation season?

The array keeps generating and the pump does not, and because an irrigation connection must carry no other load, that output exports. About 20 percent of a year's generation falls between May and August in our model, and the shoulder months add more. Export earns your retailer's buy-back, which on a spot-linked plan moves with the wholesale price.

How big an array should a pivot have?

Size it in kW against the pump, not in panels against the roof. Keep the array at or below the pump's power so a running pump uses everything it makes. In our example the payback changes little between a quarter of the pump's power and all of it, so the choice comes down to how much pumping you can move into daylight and how much capital you want to commit.

What are the disadvantages of solar for irrigation?

They are all about timing. Pumps often run at night, or flat out through dry spells whatever the sun is doing; the capacity charge that makes up most of an irrigation lines bill stays the same; and outside the season the output exports. A wet summer cuts pumping and the saving with it, and drought can bring water restrictions that cut it too.

For your industry and region

Test your pump against the sun

The calculator values solar at the rate an irrigation connection actually avoids. Two minutes, no contact details; a feasibility study then runs your own pump and pumping pattern.

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