Solar for irrigation: the best daytime load there is
Michael Wilkins · Updated 11 July 2026
The short answer
Pumped irrigation is the best daytime load for solar in New Zealand: pumps run hardest through the dry, sunny months when panels generate most, so a system sized to the pumping profile self-consumes its output rather than exporting at a low rate. Canterbury holds around two thirds of national irrigation, pairing the best load with a rising power cost.
Why irrigation and solar fit so well
Pumped irrigation is the best daytime load for solar in New Zealand. Pumps draw hardest through the dry, sunny months, exactly when panels generate most, so an array sized to the pumping profile offsets that load in real time. Canterbury holds around two thirds of the country's irrigation, which is why the region pairs the best daytime load with a real and rising power cost.
Self-consumption is the whole point
Self-consumed solar avoids the 25 to 45 cent retail rate you would otherwise pay; exported solar earns only 7 to 17 cents. Irrigation is valuable precisely because it lets you use generation on site instead of exporting it. We size to the daytime pumping load so most of what the array makes offsets full-price power. The mechanics are in our guide to buy-back rates and why self-consumption wins.
Direct-coupled or grid-tied?
Most schemes are best served by a grid-tied array on the same connection as the pumps, so generation offsets pumping whenever both are running and the grid covers the rest. Off-grid direct-drive suits only isolated pumps with no connection. Either way the design follows a half-hourly analysis of your actual pumping, not a rule of thumb, which is what the feasibility study provides.
For the region-specific numbers, see our Canterbury irrigation page, or run a first estimate in the calculator below.
Run your own numbers
Conservative assumptions, fully disclosed, no contact details needed.
Your indicative numbers
Conservative, ex GST, modelled not promised
System size
72 kW
Sized to your daytime load
Installed cost
$112,320 to $152,640
Confirmed with certified installers
Investment Boost, year one
about $7,419
A 20% immediate tax deduction, worth this in cash at the 28% company rate. Not a discount.
Estimated annual saving
$18,662 to $22,118
80% of generation used on site
Indicative payback
5 to 7.5 years
Net of the Investment Boost benefit
Asset life
25+ years
Panels keep producing long after payback
Bank green business loans: 1.0% for 3 years
Your current bill
$4,000/month
Loan repayment
$2,257/month
Estimated saving
$1,699/month
The loan caps at $80,000, so the repayment shown covers that portion; the remainder is financed separately. The full financing stack is part of the feasibility study.
On these numbers the monthly repayment of $2,257 sits at or below your current bill of $4,000 while the loan runs, and the power keeps getting cheaper after it ends.
How this is modelled (assumptions v2026-06-v3)
- Power valued at $0.25 to $0.30/kWh ex GST (savings are never valued at the top of the commercial tariff range).
- 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 1200 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.
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
Why is irrigation the best load for solar?
Pumped irrigation is a large load that runs through daylight in the dry months, exactly when solar produces most. Generation and demand rise and fall together, so a system sized to the pumping profile uses most of its output on site instead of exporting it at a low buy-back rate. No other common farm load matches solar so closely.
Can solar power an irrigation pump directly?
In practice the array feeds the same connection the pumps draw from, so generation offsets pumping in real time whenever the sun is up and the pumps are running. It is not an off-grid direct-drive system; it is a grid-tied array sized so that daytime pumping consumes the generation rather than exporting it.
What does irrigation power cost, and how much can solar offset?
Irrigation including electricity cost around 31 cents per kilogram of milk solids on the average irrigated Canterbury dairy farm in 2020-21 (Farmers Weekly), and farm power prices have risen sharply since. A system sized to the pumping load can offset a large share of daytime consumption at the 25 to 45 cent retail rate you would otherwise pay.
What happens outside the irrigation season?
Irrigation runs hardest through the sunny months, so generation and pumping rise and fall together, which is ideal. Out of season the array still offsets any other load on the connection and exports the surplus. The annual model accounts for the full seasonal shape rather than assuming year-round pumping.
How big a system does an irrigation scheme need?
It follows the pumping load, not a rule of thumb. Schemes range from a single large pump to megawatt-scale networks, so we size against your half-hourly demand and daytime pumping profile. The aim is to cover the daytime pumping base without exporting heavily, because export earns a fraction of the retail rate you avoid.
For your industry and region
More from this guide
- Commercial solar in New Zealand: costs, payback and how to decide
- Investment Boost on solar: what the 20 percent deduction is actually worth
- Solar buy-back rates for businesses: export is not the prize
- What a commercial solar feasibility study includes, and when you need one
- Solar finance for NZ businesses: loans, PPAs and what actually stacks
- Solar power for dairy farms: the honest numbers
- Solar for wineries and vineyards: Marlborough to Central Otago
- Solar for cold stores and packhouses: refrigeration is the load
Size it to your pumping load
The calculator models self-consumption first and treats export at the bottom of the range. Two minutes, no contact details.