Dairy Farm Solar Canterbury: Solar that pays on your chilling, effluent and hot water loads
The short answer
Solar pays on Canterbury dairy farms with daytime load: effluent pumping, milk chilling and water heating, not the pre-dawn milking peak. A typical 30 kW shed system costs $54,000 to $78,000 installed in 2026, and EECA's Kaiwaiwai case shows a 54 kW array saving $17,000 to $20,000 a year.
Canterbury runs the largest dairy herd in the country, and its farms carry the daytime loads that make solar work: milk chilling, effluent systems and water heating. Milking itself peaks before dawn, so the honest solar case is built on those all-day loads, not the shed. Where they are present, and in Canterbury they usually are, the numbers stack.
We are not an installer. Involve Energy models the system against your own bills, arranges the financing stack and project-manages SEANZ-certified local crews through to commissioning, so you get an owned asset, an independent model and one point of accountability.
Where solar pays on a Canterbury dairy farm
- Effluent pumping: it runs in daylight on the shed's own connection. Irrigation pumps sit on a dedicated connection of their own and are a separate case.
- Milk chilling and refrigeration: compressors cycle all day, every day of the season.
- Water heating: shift cylinder heating onto daytime timers and it becomes a solar load.
- The wider connection: pump sheds, workshops and dwellings on the same ICP soak up generation that would otherwise export.
The full picture, including the pre-dawn milking caveat and a worked EECA example, is in our guide to solar for dairy farms.
How it works
01
Feasibility
Send twelve months of power bills, ideally half-hourly data. We model system size, generation against your actual load, self-consumption, cost, savings and payback on your numbers, not industry averages.
02
Financing
We apply the Investment Boost deduction and match the remainder to the best available green or interest-free business lending, sized so the repayment sits at or below your current bill wherever the numbers support it.
03
Installation
Certified local crews install and commission the system. We manage the lines company approval, the electrical certification and the programme around your milking and irrigation calendar.
04
Monitoring
Once live, we watch performance, flag anything underperforming and report your actual savings against the model, year after year.
Start with a conservative estimate in the calculator below, then send a year of bills for the half-hourly version. The Investment Boost and financing options are explained in full in the guides.
The numbers
What the numbers look like
| System size | Indicative installed cost | Indicative annual saving | Indicative payback |
|---|---|---|---|
| 30 kW | $54,000 to $78,000 | $7,000 to $8,000 | 6.5 to 11 years |
| 60 kW | $98,000 to $135,000 | $13,000 to $16,000 | 6 to 10 years |
| 100 kW | $140,000 to $180,000 | $22,000 to $27,000 | 5 to 8 years |
| 250 kW | $275,000 to $375,000 | $55,000 to $66,000 | 4 to 6.5 years |
Cited references
Worked examples from real sites
Industry referenceFeatherston, Wairarapa
Kaiwaiwai Dairies
Kaiwaiwai Dairies in the Wairarapa installed a 54 kW ground-mounted array in 2021 for about $110,000; it saves $17,000 to $20,000 a year, a five and a half to six and a half year payback. More than 90 percent of generation is used on site across irrigation, effluent and chilling; export income is only about $267 a year. The farm is now an EECA Solar on Farms demonstration site, listed in May 2026 at 288 kW with batteries. Figures as published by EECA.
- System
- 54 kW
- Installed cost
- $110,000
- Annual saving
- $18,500
- Payback
- 6 years
Source: EECA case study
Your numbers
Start from the example. Put in yours.
Your farm or business
Your indicative numbers
Conservative, ex GST, modelled not promised
Measure
- Power used
- 164,706 kWh a year
- Your spend at 25.5c a kWh ex GST, the national commercial average.
- Power bill
- $42,000 a year
Design
- System
- 51 kW
- Sized to your daytime load.
- Generates
- 66,810 kWh a year
- Used on site
- 70%
- The rest exports at 8c a kWh.
- Installed cost
- $85,680 to $120,360
- Confirmed with certified installers.
Finance
- Investment Boost, year one
- about $5,769
- A 20% immediate tax deduction, worth this in cash at the 28% company rate. Not a discount.
- ASB Smart Solar Loan
- $1,717 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
- $1,028 a month
- Mid estimate, set against the repayment while the loan runs.
Outcome
- Saving
- $11,144 to $13,529 a year
- Payback
- 6 to 10 years
- Net of the Investment Boost benefit.
- Emissions avoided
- 3.5 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 $0.20 to $0.26/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 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 on a Canterbury dairy farm?
Often, where there is real daytime load. Milking peaks before dawn, so solar pays on effluent pumping, milk chilling and water heating instead, and Canterbury farms tend to run all three. A half-hourly analysis of your year of usage gives the honest answer before you spend anything.
Does solar pair well with irrigation pumping?
Not on the shed's connection. In Canterbury, irrigation pumps over 20 kW sit on a dedicated irrigation connection billed mostly for pump capacity, so they need an array of their own, and solar there pays only when pumping moves into daylight. DairyNZ puts the median irrigation cost on Canterbury owner-operator farms at $0.27 per kg of milksolids in 2024-25. Our Canterbury irrigation page models it.
What size system does a dairy shed need?
Installers commonly quote around 30 kW for a typical rotary shed, roughly 55 to 70 panels, producing 150 to 200 kWh a day in the peak milking month. The right size follows your daytime load, not the shed, which is what the feasibility study works out.
How do Canterbury farmers pay for solar?
Most stack the Investment Boost tax deduction (20 percent immediate deduction on new assets) with rural green lending. ASB has offered a Smart Solar Loan at 0 percent for five years on up to $150,000 of on-farm solar and battery for rural customers; dated offers like this lapse and renew on bank timetables, so we only ever show what is live on the day you run the numbers.
What about winter, when the cows are dried off?
South Island winter output runs around 40 to 60 percent of summer, which matches dairying reasonably: the heavy chilling months are also the high-sun months. The annual model we publish accounts for the full seasonal shape month by month rather than averaging it away.
See your farm's numbers before you commit
Send a recent power bill and we will model system size, cost, savings and payback against your actual usage, the pre-dawn caveat included. Independent, no obligation, yours to keep.