The complete guide
Commercial solar in New Zealand: costs, payback and how to decide
Michael Wilkins · Updated 2 October 2026 · 5 min read
The short answer
Commercial solar in New Zealand costs roughly $1,400 to $1,800 per kW installed at 100 kW in 2026. Our worked examples pay back in 4.5 to 10 years where load runs in daylight, longer on dairy farms that milk before dawn. The Investment Boost deduction returns about 5.6 percent of cost in year-one tax cash for a company.
How much does commercial solar cost in NZ?
Installed cost falls fast with scale. As at mid 2026 we work to roughly $1,800 to $2,600 per kW at 30 kW, $1,400 to $1,800 per kW at 100 kW, and $1,100 to $1,500 per kW at 250 kW and beyond. These are the same bands our public calculator uses, and EECA's commercial guidance of $1,500 to $2,000 per kW (October 2024) sits inside them. The table puts whole-project numbers on it, with what each size makes a year in Canterbury.
| System size | Cost per kW | Installed cost | Investment Boost, year-one tax cash | Output a year, Canterbury |
|---|---|---|---|---|
| 30 kW | $1,800 to $2,600 | $54,000 to $78,000 | $3,000 to $4,400 | 39,000 kWh |
| 50 kW | $1,690 to $2,370 | $84,000 to $119,000 | $4,700 to $6,600 | 66,000 kWh |
| 100 kW | $1,400 to $1,800 | $140,000 to $180,000 | $7,800 to $10,100 | 131,000 kWh |
| 250 kW | $1,100 to $1,500 | $275,000 to $375,000 | $15,400 to $21,000 | 328,000 kWh |
| 500 kW | $1,100 to $1,500 | $550,000 to $750,000 | $30,800 to $42,000 | 655,000 kWh |
Two things move you inside the band: roof complexity (steel trapezoidal roofs in good condition are cheapest; ground mounts add structure but can chase better angles) and how competitive the installer tender is. We run that tender across SEANZ-certified installers rather than taking a single quote.
From 22 May 2025 the Investment Boost deduction lets a business deduct 20 percent of a new solar system's cost immediately, with the remaining 80 percent depreciating as normal. For a company taxpayer at the 28 percent rate that is worth roughly 5.6 percent of the project cost in year-one tax cash. It is a deduction, not a discount, and we state it that way everywhere.
What payback should you expect?
Vendor marketing claims four to eight year paybacks and 15 to 25 percent returns for good sites. Treat those as the optimistic end. What actually decides your payback is the share of generation you consume on site: every kWh you self-consume avoids the per-kWh charges on your bill, 20.4 to 25.5 cents in our model, while every kWh you export earns a retailer buy-back of typically 7 to 17 cents. That gap is the whole game.
Region matters too. Our modelled yields, derated about 10 percent from satellite data to reflect real commercial installs, run from about 1,220 kWh per kW a year in Central Otago to 1,310 in Canterbury and 1,140 in Southland. Sunnier sites generate more, but a Southland dairy shed with the right daytime load can still beat a poorly matched Central Otago site. Load shape beats latitude.
| Region | kWh per kW a year | What 100 kW makes a year |
|---|---|---|
| Marlborough | 1,390 | 139,000 kWh |
| Nelson Tasman | 1,330 | 133,000 kWh |
| Canterbury | 1,310 | 131,000 kWh |
| Central Otago | 1,220 | 122,000 kWh |
| Coastal Otago | 1,220 | 122,000 kWh |
| Southland | 1,140 | 114,000 kWh |
| West Coast | 1,120 | 112,000 kWh |
The same data for 21 individual towns, from Blenheim to Westport, is in South Island solar by town.
The full mechanics, including why export rates barely move the result, are in our guide to buy-back rates for businesses.
Is commercial solar worth it for your business?
Commercial customers paid an average 25.5 cents a kWh ex GST in the year to March 2026, 52.5 percent more than in the year to March 2018 (MBIE), and the Commerce Commission's 2025 reset lets several South Island lines companies raise their revenue faster than inflation each year to March 2030. Solar is a hedge you own: it turns part of an open-ended operating cost into an asset we model over 25 years.
The businesses where the numbers work hardest share three things:
- Daytime load: refrigeration, processing, compressed air, cool stores, or irrigation pumping moved into daylight, running while the sun is up.
- A usable roof or land: north-facing steel roofs in sound condition, or paddock corners for ground mounts.
- A planning horizon past five years, so the owner, not the next tenant, banks the savings.
Our answer by daily pattern and region, including where solar is not worth it, is in is solar worth it for a NZ business. To go deeper by kind of business: farm solar for dairy, irrigation, orchards and vineyards; commercial solar in Christchurch for warehouses, workshops, offices and schools; and manufacturing and logistics in Canterbury for plants with day shifts.
Payback by industry: worked examples
Payback depends far more on when you use power than on what you make. The table runs one example site per industry through our calculator, each sized to the share of its bill that falls in daylight hours. Refrigeration and processing loads run with the sun and pay back fastest; irrigation pays only where pumping moves into daylight.
| Example site | Power bill a month | System | Installed cost | Saving a year | Payback |
|---|---|---|---|---|---|
| Dairy farm, Canterbury | $3,500 | 34 kW | $60,000 to $87,000 | $6,600 to $7,900 | 7.5 to 12.5 years |
| Irrigation pumping site, Canterbury | $5,000 | 97 kW | $137,000 to $178,000 | $14,900 to $19,700 | 6.5 to 11 years |
| Packhouse and cold store, Central Otago | $6,000 | 125 kW | $169,000 to $219,000 | $27,300 to $33,600 | 4.5 to 7.5 years |
| Winery, Marlborough | $4,000 | 55 kW | $91,000 to $127,000 | $12,800 to $15,500 | 5.5 to 9.5 years |
| Seafood processor, Marlborough | $8,000 | 110 kW | $152,000 to $196,000 | $25,500 to $31,000 | 4.5 to 7 years |
| Manufacturing and logistics site, Canterbury | $8,000 | 116 kW | $159,000 to $205,000 | $25,300 to $30,800 | 5 to 7.5 years |
| Commercial site, Canterbury | $4,000 | 58 kW | $95,000 to $132,000 | $12,700 to $15,400 | 6 to 10 years |
Dairy is the honest outlier: milking peaks before dawn, so less of the generation lands on the farm's own load. Dairy solar pays on effluent pumping, chilling and water heating instead, which is why our dairy guide sizes to those loads. How every number here is built, and what the calculator cannot know about your site, is set out in how we model.
How the buying process works
01
Analyse a year of usage
Half-hourly consumption data for 12 months, the method EECA recommends, shows exactly when you use power and how much a panel array would actually offset.
02
Independent feasibility study
Sizing, satellite irradiance for your site, costs from current bands, financing and incentives, and a 25-year cash flow with disclosed assumptions.
03
Arrange the financing stack
Green loans, the Investment Boost deduction and any live offers, stacked cheapest rate first. Claims like cashflow positive only get made when the whole cost is covered.
04
Tender and install
SEANZ-certified installers price the specified system competitively. Installation on a commercial roof typically runs days to a few weeks, not months.
What a proper study contains, and the red flags in free vendor assessments, is covered in our feasibility study guide.
Commercial solar is the laggard, which is the opportunity
Financing has also caught up: between the Investment Boost deduction and bank green lending, including dated offers like the ASB Smart Solar Loan for rural customers, most viable projects can now be structured so repayments sit below the power-bill savings for a sensible term. The financing guide compares the options honestly, including what happens when offers lapse.
Your numbers
Run your own numbers
Your farm or business
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
- 83 kW
- Sized to your daytime load.
- Generates
- 101,260 kWh a year
- Used on site
- 80%
- The rest exports at 8c a kWh.
- Installed cost
- $124,263 to $165,526
- Confirmed with certified installers.
Finance
- Investment Boost, year one
- about $8,114
- A 20% immediate tax deduction, worth this in cash at the 28% company rate. Not a discount.
- ASB Smart Solar Loan
- $2,415 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
- $1,684 a month
- Mid estimate, set against the repayment while the loan runs.
Outcome
- Saving
- $18,146 to $22,277 a year
- Payback
- 5.5 to 8.5 years
- Net of the Investment Boost benefit.
- Emissions avoided
- 6.0 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.
- Central Otago and Queenstown Lakes yield modelled at 1220 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
How much does commercial solar cost in NZ?
As at mid 2026, expect roughly $1,800 to $2,600 per kW installed at 30 kW, $1,400 to $1,800 per kW at 100 kW, and $1,100 to $1,500 per kW at 250 to 500 kW. A 100 kW system therefore lands around $140,000 to $180,000 before the Investment Boost tax deduction. EECA's published guidance of $1,500 to $2,000 per kW sits inside these ranges.
What is the difference between residential and commercial solar?
Scale, load and tax. Commercial systems run from about 30 kW to 500 kW or more, against 5 to 10 kW on a house, and cost less per kW as they grow. Businesses use most of their power in daylight, so more of the output is used on site. Systems over 10 kW go through the lines company's full connection application, and a business can claim the Investment Boost deduction and depreciation, which households generally cannot.
What payback can a business expect from solar?
Vendors commonly claim four to eight years for good commercial sites. The honest answer depends on how much generation you use on site: self-consumed power avoids the per-kWh charges on your bill, 20.4 to 25.5 cents in our model, while exports earn only 7 to 17 cents. High daytime loads in sunny regions sit at the fast end; we model conservatively and show the assumptions.
How long do commercial solar panels last?
EECA's commercial solar guidance puts panel life at 30 plus years with output declining around 0.8 percent a year, and inverter life around 15 years. We model 0.5 percent annual degradation, between vendor claims of 0.4 and EECA's conservative figure, and include an inverter replacement in the cash flow at year 13.
Does a business need a battery with solar?
Not to start. A battery shifts daytime generation into evening use and can keep critical loads running through outages, but it adds cost that often slows the headline payback. If your load is mostly in daylight hours, panels alone usually stack first. We model batteries separately so the numbers, not the bundle, decide.
What size solar system does my business need?
Size to your daytime consumption, not your roof. The aim is to cover most of what you use while the sun is up without exporting heavily, because exports earn far less than the retail rate you avoid. A monthly power spend of $2,000 to $5,000 with daytime operations typically points at 30 to 100 kW; a half-hourly analysis of 12 months of usage settles it.
What is the 20% rule for solar?
A household rule of thumb: build enough panels to produce about 20 percent more than you use in a year, so the surplus covers cloudy months. It comes from markets that credit exports near the retail rate. In New Zealand exports earn 7 to 17 cents per kWh while power used on site avoids 20.4 to 25.5 cents in our model, so a business should size to its daytime load instead. It has nothing to do with the Investment Boost, a 20 percent tax deduction.
For your industry and region
Put your own numbers on it
Two minutes in the calculator with conservative, disclosed assumptions, or book an independent feasibility study and get the full model.