We Built a 145kW Farm Solar System
— Here's What It Actually Costs and Delivers
Most farm solar content in New Zealand tells you solar is a good idea and stops there. It isn’t hard to find that opinion — it’s harder to find the load data, the real quotes, and a system that’s actually running on a working farm right now. This article has all three.
We’ll start with a system Trilect Solar built and commissioned ourselves — the MacKenzie solar shed conversion — then work through the EECA cost data, the DairyNZ milking shed numbers, and the horticulture and irrigation case that most solar on farm content skips over.
Inside the MacKenzie Farm Solar Shed Conversion — 145kW and Zero Downtime
On MacKenzie Farm solar installation project, Trilect converted the property’s existing sheds into a 145.145 kW solar array — 319 panels at 455W each — paired with 84.42 kWh of battery storage across seven 12 kW battery units. It’s not a single-shed pilot: the system now runs every shed and every home on the property.
The part that makes this project worth studying isn’t the panel count, though — it’s the backup logic. A genset is integrated directly into the system, so the hierarchy is: solar covers daytime load and charges the batteries, the batteries carry the property overnight, and the genset only starts automatically if the batteries run low. Power cuts aren’t something the farm has to plan around anymore. That’s the actual promise of on-farm solar — not “cheaper power on sunny days,” but a property that doesn’t notice when the grid drops out.
We’ll come back to why that backup structure matters more than system size on its own once we’ve been through the shed conversion case below. For now, the headline is this: a solar shed conversion doesn’t have to mean “panels on one roof, offsetting one bill.” Done properly, it can mean the whole property runs on it.
Is farm solar actually catching on in New Zealand, or is this still niche?
It’s catching on, but adoption is running behind interest — which is exactly the gap a project like MacKenzie’s sits ahead of. New Zealand had 855 MW of distributed solar installed by the end of January 2026, plus 247 MW in grid-connected solar farms, and capacity has roughly doubled every 24 months since records began in 2013 (According to the Electricity Authority). Commercial and agricultural sites are building bigger than the average homeowner too: new SME systems installed in January 2026 averaged 20 kW, against 7.9 kW for households.
The clearest signal of where farm demand actually sits comes from EECA’s own numbers. More than 230 farms applied for just 40 places in the government’s Solar on Farms co-funding round, with $2.116 million committed to the first 32 confirmed sites — covering 40% of inverter-and-battery costs and 20% of the rest of the array. And in an EECA survey of 220 farmers, almost 80% hadn’t yet installed solar but said they were open to it. Translation: most farmers aren’t asking “is this a good idea,” they’re asking “what does it actually cost, and will it hold up.” Fair questions — here’s the honest answer.
What does a farm solar system actually cost?
This is the number most farm solar pages either avoid or bury. EECA has published real quote data pulled directly from New Zealand farms going through the process, not modelled estimates:
- Small systems (around 20 kWp) start from roughly $30,000, excl. GST.
- Large systems (around 200 kWp) typically run $250,000–$300,000, excl. GST.
- Batteries add $700–$1,200 per kWh installed.
- Switchboard or meter upgrades, line upgrades for export, site access, and roof vs ground mounting all move the final number.
On payback, EECA’s modelling — $1.50/W capital cost, 17% capacity factor, 30c/kWh avoided grid cost, 10c/kWh export revenue, 75% self-consumption — lands on a simple payback of as little as 4 years for a solar-only system with high self-use. After that it’s close to free power for the remaining ~21 years of a 25-year panel life. Add a battery, and payback stretches out — but so does resilience, which is precisely the trade-off MacKenzie Farm made and why the genset integration matters as much as the panel count.
The Load Data Behind Milk Shed Solar
Milking shed solar gets talked about more than any other farm application in New Zealand, and the underlying numbers explain why. A DairyNZ and EECA-backed audit of 150 dairy farms across the Waikato, Lower North Island, Canterbury and Otago/Southland found:
- The average dairy farm milking operation, including irrigation, used 112,100 kWh per season.
- Dairy farms account for 2.3% of New Zealand’s total electricity consumption, and the average farm spends over $14,000 a year on power.
- Water heating made up 24% of milking shed electricity use, water pumping 22%, refrigeration 17%, vacuum pumps 15%.
- Farms cut consumption by up to 16% through efficiency measures alone, before solar even enters the picture.
The reason milk shed solar performs well isn’t complicated: milking draws heavy load twice a day, in short windows that overlap daylight hours for most of the season. A Southland installation near Mataura backs this up in practice — a 73.71 kW array with a 100 kWh battery now covers roughly 75% of a new shed’s seasonal electricity use, at generation costs around a quarter of the farm’s previous retail rate. Kaiwaiwai Dairies runs a similar story at smaller scale: a 54 kW array delivering over 90% self-consumption across milking, chilling, irrigation and effluent processes.
Horticulture Solar and Irrigation Run on a Different Load Entirely
Horticulture solar leans on a different set of loads than dairy — irrigation pumping, frost protection, and continuous cool store refrigeration rather than twice-daily milking spikes. The economics for irrigation in particular are stark once you put solar next to diesel: an 18.5 kW pump irrigating roughly 9,600 trees on diesel burns about 5.5 litres an hour, against a fraction of that cost from a solar-fed system running the same load. Central Otago’s Forest Lodge Orchard takes this furthest of anyone in the country — a 160 kW array with 300 kWh of battery storage running electric tractors, frost fans, and irrigation pumps on a fully fossil-fuel-free 6-hectare site.
The lesson for horticulture growers is the same one MacKenzie Farm demonstrates for dairy: solar sized against continuous or predictable loads — cool stores, irrigation schedules — pays back faster than solar sized as a rough percentage of roof space.
Why Solar Shed Conversion Is Often the Fastest Way In
A solar shed conversion — panels on an existing dairy shed, implement shed, workshop, or cool store roof, like MacKenzie Farm — is usually the fastest and cheapest route onto solar, for a few practical reasons:
The structure and footings already exist, so there’s no new land take and generally less consent friction than a ground-mount array.
Most rural sheds are structurally sound enough for panels without expensive reinforcement.
Cool stores convert particularly well, since continuous refrigeration load matches daytime solar output almost exactly.
It’s still licensed electrical work — a shed conversion at farm scale is not a DIY project once you’re past a basic off-grid kit.
Consent treatment also shifts sharply with scale. Rewiring Aotearoa’s Mike Casey has drawn a useful line here: farm-scale solar powering a shed or irrigator is generally treated as a temporary, removable structure — no different to fence posts — while ground-mount arrays above roughly 1 MW face genuinely different consent requirements. MacKenzie Farm’s 145 kW sits well inside the first category, which is part of why shed conversions move faster from quote to commissioning than paddock-based farms.
What this means for your farm
The pattern across every reliable New Zealand data source — EECA, DairyNZ, and projects like MacKenzie Farm — is the same: farm solar performs best when it’s sized against your actual load, not a generic percentage of roof space. Milking sheds, cool stores, and irrigation pumps all carry different daily and seasonal demand curves, and the systems that hold up (McKenzie Farm, Kaiwaiwai Dairies, Forest Lodge Orchard) were all designed around measured on-farm usage rather than a standard package.
Ready to see what this looks like on your farm?
Every number in this article — the $30,000 starting point, the 4-year payback, the 112,100 kWh season, the 145.145kW at MacKenzie — came from a real quote, a real audit, or a real installation. None of it is a generic estimate, and neither should your system be.
Trilect Solar designs farm solar systems around your actual load: milking times, irrigation schedules, cool store runtime, whatever’s driving your power bill. That’s what made MacKenzie Farm work, and it’s the same process we’d run for your property.
If you’re ready to find out what a solar shed conversion, milk shed solar system, or irrigation solar setup would look like on your farm, get in touch with Trilect Solar today. Request a quote, and we’ll model your numbers against current EECA cost and payback benchmarks — no generic package, just a system sized to what your farm actually uses. You can also browse our commercial solar energy system installations or see more completed solar projects like MacKenzie Farm.
frequently asked questions
Is solar worth it for a dairy farm?
Based on EECA’s real farm quote data, a solar-only system with high self-consumption can pay back in around 4 years, then run largely free for the rest of its 25-year life. Farms with heavy daytime loads — milking, irrigation, refrigeration — see faster returns than farms with flatter usage.
How much does a farm solar system cost in NZ?
Small systems (around 20 kWp) start from about $30,000 excl. GST; larger 200 kWp systems typically run $250,000–$300,000 excl. GST, before batteries. Batteries add $700–$1,200 per kWh installed.
Is there government funding for solar on farm projects?
Yes. EECA’s Solar on Farms programme has funded up to 40% of inverter-and-battery costs and up to 20% of the rest of a solar array, capped per site. The current round is fully allocated across roughly 40 demonstration farms, but it signals real, ongoing government appetite to support agriculture solar — and EECA runs a dedicated solar helpline for farmers year-round.
Do I need resource consent for farm solar?
Small, farm-scale solar for a shed or irrigator is generally treated as a temporary structure and typically doesn’t need consent — McKenzie Farm’s 145 kW system falls into this category. Ground-mount arrays above roughly 1 MW are assessed differently and usually do require consent. Rules vary by council, so check locally before committing to a layout.
Should I mount panels on my shed roof or on the ground?
Roof-mounted shed conversions are usually cheaper and faster where the roof structure and orientation suit it, and they don’t use up productive land — that’s the approach behind McKenzie Farm. Ground mounting gets chosen where roof strength or angle isn’t ideal, or site access favours it.
Is a battery necessary?
No, and it can be added later. But without one, a solar system typically won’t run your shed during a grid outage — the genset-backed battery setup at McKenzie Farm is what actually removes outages as a concern, not the panels alone.
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