Commercial Solar Payback: What New Zealand Businesses Can Expect

For most New Zealand businesses, commercial solar pays for itself in roughly 4 to 8 years, with the strongest cases (a dairy shed running pumps and chillers through the day, or a workshop humming from 8am to 5pm) landing nearer 4 to 6 years, and the weaker ones (an office that's busy but uses little actual power, or a building empty by mid-afternoon) stretching out to 8 to 10 years. The single biggest lever is not the size of your roof or the price of panels. It's how much of your power you use during daylight hours. Get that right and the maths is genuinely good. Get it wrong and you're exporting low-value power and buying it back at the full retail rate.

That gap matters because a commercial system is real money. A 30kW commercial install typically runs $45,000 to $70,000 before GST in 2025, depending on roof type, switchboard work and whether you need new cabling, per pricing across SEANZ-affiliated installers and MBIE commercial solar data. So a year or two either way on payback is tens of thousands of dollars of difference. It pays to understand what's actually driving your number before you sign anything.

Why daytime load is the whole ballgame

Solar only generates while the sun is up. The value you get from it depends entirely on what you do with that power the moment it's produced.

Every kilowatt-hour you use on site as it's generated is worth the full retail rate you'd otherwise pay, commonly 22 to 35 cents per kWh for a commercial connection depending on your retailer and network. Every kilowatt-hour you export to the grid because you weren't using it is worth only the buy-back rate, which sits far lower. We break down how those rates actually work, and why they vary so much, over here: https://nzsolaris.co.nz/commercial-and-rural-solar-in-nz/.

That difference is the entire game. A business that consumes 80% of its solar generation on site can have a payback under five years. The identical system on the identical roof, owned by a business that exports half its generation, might take eight. Same panels, same sun, wildly different return.

This is the piece installers don't always volunteer, because it's about your behaviour, not their product. The best commercial solar design starts with your load profile: a half-hourly picture of when you actually draw power across a typical week. Your retailer can usually supply this. If they can't, that's your first phone call.

What a good load profile looks like for solar

• Strong fit: consistent daytime demand, Monday to Friday and ideally weekends too; refrigeration, pumps, compressors, machinery, EV charging, HVAC running through the day.
• Average fit: standard office or retail hours with moderate daytime load, weekends quiet.
• Poor fit: evening-heavy operations (restaurants, bars), businesses that close by early afternoon, or sites with low overall consumption relative to roof size.

SME payback: the realistic range

For a typical small-to-medium business (a light-industrial unit, a workshop, a retailer, a medium office), payback usually lands in the 5 to 8 year band, with a system life well beyond that. Quality panels carry 25-year performance warranties and inverters typically 10 to 12 years, so you're looking at a decade or more of effectively free generation after payback.

Here's a worked example to make it concrete.

Worked example: an engineering workshop in Hamilton

Picture a steel-fabrication workshop on the outskirts of Hamilton, in the WEL Networks area. Big flat-ish roof, machinery running 7.30am to 5pm weekdays, a couple of compressors, decent lighting load. Annual power bill around $24,000.

• System: 40kW, fully installed at roughly $58,000 + GST
• Annual generation: around 52,000 kWh (Waikato gets solid sun; NIWA's solar resource data backs this out)
• Self-consumption: 75%, because the machinery runs through the day
• Value of self-consumed power (at ~28c/kWh avoided): about $10,900/year
• Value of exported power (at a buy-back rate of, say, 12c/kWh): about $1,560/year
• Total annual benefit: roughly $12,400

On those numbers, simple payback is around 4.7 years on the GST-exclusive cost. A registered business claims the GST back, so the real cash figure that matters is the ex-GST price. That's a return most business owners would take all day.

Now change one thing. Make it a print shop that's busy in the mornings but winds down by 2pm. Self-consumption drops to 45%, far more power gets exported at the low rate, and the same system's payback drifts out past 7 years. Same roof, same region, same install cost. The difference is purely when the power gets used.

Agribusiness payback: usually the strongest case in the country

Rural and agricultural operations often have the best commercial solar economics in New Zealand, and it comes down to load profile again. A lot of farm power demand is daytime, continuous, and unavoidable.

Dairy is the standout. Milking happens in daylight (or close to it), and the vat refrigeration, milk pumps, water pumps and effluent systems draw steady power through the day. That's close to a perfect match for solar generation. We go deep on the milking-shed and irrigation maths over here: https://nzsolaris.co.nz/dairy-farm-solar-nz/.

For a well-matched dairy or irrigation operation, payback frequently lands in the 4 to 6 year range, and self-consumption can sit at 85% or higher because the load is so consistent.

Worked example: a Canterbury dairy shed

Take a 700-cow operation on the Canterbury plains, in the Orion network area. Twice-a-day milking, vat refrigeration running hard, water and effluent pumps, plenty of clear Canterbury sun.

• System: 50kW, fully installed at roughly $70,000 + GST
• Annual generation: around 68,000 kWh (Canterbury's clear-sky days lift output; NIWA data supports the higher yield)
• Self-consumption: 85%
• Annual benefit (avoided power at ~26c plus a small export credit): roughly $15,500
• Simple payback: around 4.5 years

Irrigation is the other big agribusiness win, with a twist: pivot pumps draw enormous power, but only seasonally. If your irrigation runs hard through the sunny months (which it does, by definition), solar can shave a serious chunk off the summer demand charges that hammer rural connections. The key is sizing the system to the irrigation season without leaving it stranded and over-exporting in winter.

The thing that quietly changes every commercial payback number in 2025

Here's the piece that genuinely moves the needle and that a lot of older payback figures online completely miss: the 20% Investment Boost introduced in Budget 2025.

For qualifying new business assets (and commercial solar generally qualifies), a business can immediately deduct 20% of the asset's cost in the year it's installed, on top of normal depreciation. For a $58,000 ex-GST system, that's an extra $11,600 of deductible expense in year one. At the 28% company tax rate, that's roughly $3,250 of tax saved upfront.

Fold that back into the workshop example and the effective net cost drops from $58,000 toward the mid-$54,000s, pulling payback in by several months. It's not a handout, it's a timing benefit, but it's real cash flow in year one and it materially improves the return. We've laid out exactly how it works, what qualifies, and how to talk to your accountant about it here: https://nzsolaris.co.nz/ird-commercial-solar-tax-boost/.

One honest caveat: tax treatment depends on your structure and circumstances. Always confirm with your accountant before you bank on the number. But if you're comparing solar quotes and none of your installers has mentioned the Investment Boost, they're working off out-of-date economics.

What actually drives your number (and what doesn't)

In rough order of impact on payback:

• Self-consumption rate. By a mile the biggest factor. Move from 50% to 80% self-consumption and you can knock years off.
• Your current power price. The higher the rate you're paying now, the more each self-consumed unit saves you. Businesses on demand-charge tariffs often benefit more than the headline unit rate suggests.
• Demand charges. Many commercial connections pay a charge based on peak demand. Solar can trim daytime peaks, and on some tariffs that's worth more than the energy savings. This is genuinely under-discussed and worth modelling specifically for your connection.
• Network area and buy-back rate. Vector (Auckland), Orion (Canterbury), Powerco and the rest all set different lines charges, and retailers set wildly different buy-back rates. The export rate matters less the more you self-consume.
• Region and roof orientation. Real, but smaller than people assume. A north-facing roof in Christchurch with clear winter skies can out-generate a similar roof in cloudier Auckland or the West Coast. NIWA's solar data shows Canterbury and Central Otago among the best in the country for clear-sky generation.
• Install quality and price. Matters, but a low-cost system that's poorly designed for your load profile is a false economy.

Where commercial solar doesn't pencil out

The brand here is honesty, so let's be straight about who should think twice.

• Evening-heavy businesses. Restaurants, bars and late-trading hospitality generate solar at midday and need power at night. Without a battery (which lengthens payback considerably) the maths is weak.
• Low-consumption sites with big roofs. A warehouse with a huge roof but modest power use will export most of its generation at low rates. Tempting visually, poor financially.
• Short tenancy or uncertain occupancy. If you lease and you're not sure you'll be in the building in five years, the payback case gets shaky unless you can negotiate the system into the lease or building value.
• Businesses planning to relocate or sell soon. Solar adds value to a commercial building, but you may not capture the full payback if you move before year five or six.

None of these are dealbreakers in every case, but they all need a clear-eyed look at the load profile before you commit.

How to nail down your own payback number

Before you take an installer's payback figure at face value, do this:

• Get your half-hourly data. Ask your retailer for at least 12 months of half-hourly consumption data. This is the single most useful thing you can do. It shows your real load shape, not an assumption.
• Check your tariff structure. Find out whether you pay demand charges, and what your actual per-kWh rate is across the day. Many businesses don't know their own tariff in detail.
• Run the numbers yourself first. Before the sales conversation, get a feel for the ballpark using our commercial calculator: https://nzsolaris.co.nz/commercial-solar-roi-calculator/. If you want a simpler starting point, the general tool here is useful too: https://nzsolaris.co.nz/solar-roi-calculator/.
• Make every quote show the self-consumption assumption. If a payback figure doesn't state what self-consumption percentage it assumes, it's meaningless. Push for it.
• Confirm the Investment Boost is factored in. And check it with your accountant.

What to ask every installer

• "What self-consumption rate is your payback based on, and how did you work it out from my data?"
• "Have you sized this to my daytime load, or just to fill my roof?"
• "What happens to the export rate, and how much of my generation will I be exporting?"
• "Does your figure include the 20% Investment Boost and GST treatment for a registered business?"
• "What's the inverter warranty, and what's the expected replacement cost in year 12?"

A good commercial installer will welcome these questions and answer them with your data in hand. One that waves them away and pushes a roof-filling system is selling panels, not solving your power bill.

Frequently Asked Questions

What's a realistic payback period for commercial solar in NZ?

For most businesses, 5 to 8 years, with strong daytime-load operations like dairy sheds and workshops often hitting 4 to 6 years. Evening-heavy or low-consumption businesses can stretch beyond 8 years. The deciding factor is how much of your generation you use on site rather than exporting.

Why does self-consumption matter so much?

Power you use as it's generated saves you the full retail rate, commonly 22 to 35c/kWh for a commercial connection. Power you export earns only the buy-back rate, which is far lower. A business at 80% self-consumption can pay off the same system years faster than one at 50%, even with identical panels and sun.

Is solar better for farms than for offices?

Often, yes, because farm load tends to be steady and daytime-heavy. Dairy refrigeration, pumps and irrigation draw power right through the sunny part of the day, which matches solar generation almost perfectly. An office that empties by mid-afternoon exports more of its midday peak, weakening the return.

Does the 20% Investment Boost really change the payback?

It helps. The Budget 2025 measure lets a business immediately deduct 20% of a qualifying asset's cost in year one on top of normal depreciation, improving year-one cash flow and pulling payback in by several months on a typical system. Confirm how it applies to your situation with your accountant.

How much does a commercial system cost?

Roughly $45,000 to $70,000 + GST for a 30kW system in 2025, scaling up from there, per pricing across SEANZ-affiliated installers and MBIE data. Registered businesses claim the GST back, so the ex-GST figure is the one that matters for your return.

Do I need a battery to make commercial solar worth it?

Usually not, if your load is daytime-heavy. Batteries add significant cost and lengthen payback, so they tend to make sense for evening-heavy businesses or sites needing backup, not for operations that already use most of their power during daylight.

How do I find out my daytime load profile?

Ask your electricity retailer for at least 12 months of half-hourly consumption data. It's usually free and it shows exactly when you draw power across the day and week. This data is the foundation of any honest payback calculation, so get it before you take quotes.

Will solar wipe out my business power bill?

No, and be wary of anyone who says it will. A grid-connected system reduces your bill substantially but won't eliminate it, because you'll still draw from the grid at night and on dull days, and you'll still pay fixed and lines charges. The goal is a strong return on investment, not a zero bill.

Bottom Line

Commercial solar in New Zealand is a genuinely good investment for businesses that use power during the day, and the strongest cases (dairy, irrigation, daytime manufacturing) are among the best returns going. The number that decides everything is your self-consumption rate, which flows straight from your load profile. Get your half-hourly data, factor in the Investment Boost, and make every installer show their working.

If you'd like the fuller picture on rural and commercial systems generally, start here: https://nzsolaris.co.nz/commercial-and-rural-solar-in-nz/. And if dairy is your world, the shed-and-irrigation breakdown is worth a read before you talk to anyone: https://nzsolaris.co.nz/dairy-farm-solar-nz/.