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Solar Calculator New Zealand

Enter your region, electricity retailer, and system size — get annual savings in NZ$, buy-back income, and payback period for your NZ home.

Your solar setup
NZ$
kW
Your solar savings estimate
NZ$1,511/yr savings — 45% bill reduction
Annual solar production7709 kWh/yr
Panels needed17 × 400W panels
Self-consumption savingsNZ$956/yr
Buy-back income (12c/kWh)NZ$555/yr
Estimated system costNZ$11,880
Westpac 0% green loan (5yr)NZ$198/mo
Payback period7.9 yrs
CO2 saved per year0.66 tonnes CO2
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How to Use This Calculator

Enter your monthly bill and region

Start with your average monthly power bill — find this on your electricity invoice or in your retailer's online portal. New Zealand electricity prices average around 30-33c/kWh in 2026, but vary by retailer and plan. Select your region: Nelson and Tauranga get the most sun (4.3-4.5 PSH); Dunedin and Wellington are cloudier (3.5-3.8 PSH). Peak sun hours directly determine your system's annual output.

Choose your retailer and system size

Your electricity retailer's buy-back rate (also called solar export rate) is critical — it determines how much you earn from excess solar sent back to the grid. Ecotricity pays 21c/kWh for exported solar; Genesis pays just 8c/kWh. If you're considering switching retailers, compare buy-back rates carefully. System size: most NZ homes suit a 6.6kW system; add EV charging and you'll want 10-13kW.

Understand the results

The calculator splits savings into two components: self-consumption savings (solar you use directly, worth your retail rate) and buy-back income (excess solar exported to the grid). Self-consumption is worth more — 30-33c/kWh — versus buy-back at 8-21c/kWh, so maximising self-consumption (EV charging, heat pumps, hot water timers) improves your returns.

The Formula

Annual Production (kWh) = System kW × PSH × 365 × 0.80 efficiency × Orientation Factor Self-consumed kWh = Annual Production × 0.40 (40% self-consumption) Exported kWh = Annual Production × 0.60 (60% exported) Self-consumption Savings = Self-consumed kWh × Retail Rate (c/kWh) Buy-back Income = Exported kWh × Buy-back Rate (c/kWh) Total Annual Savings = Self-consumption Savings + Buy-back Income System Cost (NZ$) = System kW × 1000 × NZ$1.80/W Payback = System Cost ÷ Annual Savings Westpac 0% Monthly = System Cost ÷ 60 months CO2 Saved = Annual kWh × 0.085 kg/kWh (NZ grid factor)

New Zealand's grid is approximately 85% renewable (hydro, geothermal, wind) — so solar CO2 savings per kWh are lower than most countries. The grid CO2 intensity of ~85g/kWh compares to 450g/kWh in Australia and 380g/kWh in the UK. The 40% self-consumption rate is a conservative estimate for households without EV or controlled hot water — homes with EV charging or ripple-controlled hot water can achieve 50-60% self-consumption.

Example

Sarah — Medium Christchurch home with Meridian Energy (6.6kW)

Sarah owns a 3-bedroom house in Christchurch with a north-facing roof. She pays NZ$280/month to Meridian Energy and wants to know if solar makes sense for her family.

Monthly billNZ$280
RegionChristchurch (4.0 PSH)
RetailerMeridian (17c buy-back)
System size6.6 kW

Result

Annual production~6,950 kWh/yr
Panels needed17 × 400W panels
Self-consumption savingsNZ$837/yr
Buy-back incomeNZ$710/yr
Total annual savingsNZ$1,547/yr
System costNZ$11,880
Westpac 0% loan (5yr)NZ$198/mo
Payback period~7.7 years

Sarah's solar system pays for itself in under 8 years and then provides 17+ years of savings. With Meridian's 17c/kWh buy-back — above average for New Zealand — the returns are solid. If she switches to Ecotricity's 21c rate, payback drops to under 7 years. Adding a timer to shift her hot water heating to daytime solar hours would increase self-consumption from 40% to ~50%, further improving the economics.

FAQ

Solar is financially viable in New Zealand, but the economics are more marginal than Australia or the US. NZ electricity prices are moderate (28-33c/kWh), buy-back rates are low (8-21c/kWh depending on retailer), and the climate is cloudier than Australia. Payback periods of 7-12 years are typical. Solar makes the most sense if: you have a north-facing roof, you're in Nelson, Tauranga, or Blenheim, you can maximise self-consumption (EV, heat pump, controlled hot water), and you choose a retailer with a high buy-back rate like Ecotricity (21c).
Buy-back rates in New Zealand vary significantly and change frequently. In 2026: Ecotricity pays the highest at 21c/kWh flat. Meridian Energy pays 17c/kWh. Octopus Energy NZ pays 12c peak / 8c off-peak. Contact Energy pays 12c/kWh. Genesis Energy pays 8c/kWh. Rates are not regulated, so switching retailers for a better buy-back rate is a straightforward way to improve your solar returns without changing anything on your roof.
New Zealand does not have a direct solar rebate or tax credit system like Australia's STC or the US's ITC. However, there are financing incentives: Westpac's 0% green home loan provides up to NZ$20,000 interest-free over 5 years for solar installations. ASB Bank and ANZ also offer green home loans with discounted rates. Some councils offer low-interest loans through the EECA (Energy Efficiency and Conservation Authority). The main NZ incentive is net metering — the right to export surplus solar to the grid.
Solar system costs in New Zealand in 2026: 3 kW system: NZ$6,000–8,000. 6.6 kW system: NZ$11,000–15,000. 10 kW system: NZ$16,000–21,000. Prices include panels, inverter, mounting hardware, and installation. Battery storage (e.g., 10 kWh Powerwall) adds NZ$14,000–18,000. Most installers belong to the Solar Energy Association of NZ (SEANZ) and offer 10-year workmanship warranties. Panels typically carry 25-year product and performance warranties.
Absolutely — solar + EV is one of the best combinations in New Zealand. A 10-13 kW solar system can generate enough electricity to power both your home and an EV driving 15,000 km/year. An EV uses roughly 4,000-5,000 kWh/year, which a 13 kW system produces in addition to covering household needs. Timing EV charging during peak solar production (10am-3pm) maximises self-consumption and minimises grid import. Vehicles like the Tesla Model Y, Nissan Leaf, and BYD Atto 3 are popular in NZ and work well with home solar charging.

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