Is solar worth it for a NZ business? Payback by sector and region

Most answers to this question are written for households, which pay more per kWh than a business: MBIE's average was 38.3 cents including GST for households against 25.5 cents ex GST for commercial customers in the year to March 2026. A business is different in three ways: it pays less per kWh, its power use often follows a working day while the sun is up, and it can claim the Investment Boost deduction and depreciation. So the answer comes down to one thing above all: how much of the output your site uses as it is generated.

Businesses are installing it. In the year to August 2026, connections with solar in the Electricity Authority's commercial category (wholesale, retail, transport and service industries; farms and manufacturers are counted separately) rose from 2,950 to 3,586, and their capacity from 102 to 180 MW.

Our answer, by daily pattern and region

We call solar worth it when even the slow end of the payback lands inside 12.5 years, the first half of the 25 years a feasibility study models. The system then saves for at least as long again as it took to pay for itself, before any rise in power prices. The table runs one business, spending $5,000 a month ex GST on power, through our calculator in every region with six daily patterns. The calculator tells industries apart by when they use power, so each row stands for the kinds of site below it.

• Mostly in daylight (cold stores, packhouses and daytime processing): 4.5 to 8.5 years. Worth it in every region: even the slow end pays back inside 12.5 years.
• Across the day (wineries, workshops, offices and day-shift plants): 5.5 to 10 years. Worth it in every region: even the slow end pays back inside 12.5 years.
• Early and late (dairy sheds that milk before dawn): 6.5 to 13 years. Worth it in Central Otago, Canterbury, Marlborough, Nelson Tasman and Coastal Otago; only at the fast end in Southland and the West Coast.
• Pump run in daylight (irrigation with pumping moved into daylight): 6.5 to 12.5 years. Worth it in every region: even the slow end pays back inside 12.5 years.
• Pump run day and night (irrigation spread evenly across the day and night): 10 to 18 years. Only at the fast end, in every region: the slow end runs past 12.5 years.
• Pump run mostly at night (irrigation run mostly at night): 13 to 22.5 years. Not worth it anywhere: even the fast end takes longer than 12.5 years.

What moves the payback

Change one thing at a time on the same business and the region matters least. Moving it from the West Coast to Marlborough changes its payback by about a year, because the calculator gives a lower-yield site a larger system for the same bill. Moving its power use from early and late into daylight changes it by about 3.5 years, and a bill of $20,000 a month against $1,500 by about 3.5 years, since cost per kW falls with size.

A small bill does not rule solar out, but below about $1,050 a month with power used across the day ($1,550 if it is used early and late) the system sizes under 15 kW, where a home-style system is the better comparison. Without taxable income to claim the Investment Boost against, payback stretches only a little, to 6 to 9.5 years for this site. Cost by system size is in the commercial solar guide, and every assumption is set out in how we model.

Where solar is not worth it

• Power used mostly at night. An irrigation pump run mostly at night takes 13 to 22.5 years in our calculator, because the pump uses about 10 percent of the output and the rest exports. Moving pumping into daylight brings it to 6.5 to 12.5 years; the irrigation guide shows how.
• A system sized to the roof rather than the load. Exports earn about 8 cents a kWh in our model against 20.4 to 25.5 for power used on site, so a 73 kW array that exported everything would take 14 to 19 years to pay back in Canterbury. More on buy-back rates for businesses.
• Power used early and late, in some regions. A dairy shed milking before dawn models 6.5 to 13 years, and in Southland and the West Coast only the fast end pays back inside 12.5 years. It pays on the daytime loads (effluent pumping, chilling and water heating), which our dairy guide sizes to.
• A battery bought only to store surplus solar. In our battery model, storing midday solar for the evening pays back in 24.5 years or more; a battery pays only where a network charges for peak demand it can cut (battery storage for business).
• Less time on the site than the payback. If the lease ends or you expect to sell before the system has paid for itself, the savings go to whoever comes next, unless the lease or sale prices them in.
• A roof that needs work soon. EECA advises doing roof replacement or major work due within the next ten years before installing, so the panels do not have to come off and go back on.

What the payback leaves out

The calculator's payback is the cost after the Investment Boost divided by the first year's saving at today's rates. A feasibility study goes further and models 25 years from your own bills and site: output falling 0.5 percent a year, $15 per kW a year for cleaning, monitoring and repairs, and an inverter replacement of $150 per kW in year 13. EECA's commercial guidance (October 2024) expects panels to last 30 years or more and inverters about 15, and suggests a business case assume output falls 0.8 percent a year; its farm guidance puts the fall at about 0.5. Neither the calculator nor the study assumes power prices rise. Commercial prices rose 52.5 percent from the year to March 2018 to the year to March 2026 (MBIE), though wholesale prices fell in 2026; the business electricity prices guide has the detail.

How to answer it for your own site

1. 01

   Find your daylight share

   Twelve months of bills give your annual use; half-hourly readings, if your meter records them, show how much of it falls while the sun is up. That share decides the answer more than anything else on this page.

2. 02

   Run the calculator

   Your monthly spend, region and daily pattern give an indicative system size, cost, saving and payback in about two minutes, with the Investment Boost stated as tax cash.

3. 03

   Check the roof and your time on the site

   EECA advises doing roof replacement or major work due within the next ten years before installing. The payback should also land well inside the time you expect to stay.

4. 04

   Get a feasibility study

   We model your site from twelve months of bills and satellite data for your exact location, for a fixed fee credited against the project if you go ahead.