How solar payback is calculated
Simple payback divides the net installed cost by the first-year benefit after maintenance. The first-year benefit combines avoided electricity purchases and credits for exported generation.
New Zealand home solar planning
Solar payback calculator NZ
Estimate how long a household solar system could take to recover its upfront cost. Compare self-used electricity, exported generation, maintenance and a longer-term cash-flow scenario using your own NZ quote and power rates.
Last reviewed: 25 August 2026
Estimated simple payback
10.9 years
based on the first year’s net benefit and unchanged year-one conditions
First-year net benefit
$1,098
25-year net position
$21,721
Self-used solar
2,600 kWh
Exported solar
3,900 kWh
- Net installed cost
- $12,000
- First-year bill saving
- $780
- First-year export credit
- $468
- Annual maintenance
- −$150
- Modelled break-even year
- Year 11
- Generation per system kW
- 1,300 kWh/year
Projected cumulative benefit
Year 1Year 25
Simple payback is a screening measure, not a complete investment return. Compare multiple generation, price and self-consumption scenarios.
Scenario only: A calculator cannot assess your roof, shading, installation quality, future tariffs or equipment life. Obtain site-specific generation estimates and itemised quotes before making a decision.
Self-consumed versus exported solar
Electricity used in the home is valued at the entered retail rate avoided. Electricity sent to the grid is valued at the entered retailer buy-back rate, which may be different.
Annual generation and system size
Enter the expected first-year generation in kWh from a site-specific assessment. System size is shown separately so you can sense-check annual kWh per installed kW.
Long-term solar projection
The projection applies the entered annual panel degradation and electricity-price change, then subtracts the same annual maintenance allowance. It is not a guarantee or a discounted cash-flow valuation.
Solar panel payback in New Zealand
Solar payback depends on more than the purchase price. Roof direction, tilt, shading, local weather, equipment design and system losses affect annual generation. Household timing then determines how much generation is used onsite and how much is exported.
Use a recent electricity bill for the retail rate and check the actual solar buy-back offer available from a retailer. Avoid treating a national average, sales estimate or another household’s result as if it applied to your property.
Solar payback formula
Annual solar benefit
Self-consumed kWh × retail electricity rate + exported kWh × buy-back rate − annual maintenance.
Simple payback period
Net installed cost ÷ first-year net solar benefit.
Worked solar payback example
For a $12,000 system generating 6,500 kWh in year one, 40% self-consumption means 2,600 kWh is used at home and 3,900 kWh is exported. At 30 cents per kWh avoided and a 12-cent export rate, the gross first-year benefit is $1,248. After a $150 maintenance allowance, the simple payback estimate is about 10.9 years.
This example is arithmetic only. It is not a typical-price claim, quote, generation forecast or recommendation.
Is solar power worth it in NZ?
Solar may produce a stronger financial result when the installed cost is competitive, the roof has a useful generation profile and the household can use more electricity while the panels are generating. The result may be weaker when shading reduces output, most generation is exported at a lower rate, finance is expensive or major replacement costs occur.
Use the solar savings calculator to compare a conservative case, the installer estimate and a higher self-consumption case. A range is more informative than one solar return-on-investment figure.
Inputs to check before comparing solar quotes
Installed cost
Include panels, inverter, mounting, electrical work, metering, approvals and GST where they form part of the quote.
Generation estimate
Ask what shading, orientation, losses and degradation assumptions support the quoted annual kWh.
Self-consumption
Compare generation hours with when the household uses hot water, heating, appliances or EV charging.
Ongoing costs
Consider maintenance, monitoring, insurance implications and possible inverter or battery replacement separately.
Official New Zealand solar guidance
Use independent energy guidance and current electricity-market information alongside qualified installer advice and property-specific quotes.
Solar payback calculator FAQs
How is solar payback calculated?
Simple payback divides the net upfront installation cost by the first-year benefit after entered maintenance. The benefit combines electricity used in the home at the retail rate avoided and exported electricity at the entered buy-back rate.
Why does solar self-consumption matter?
A generated kWh used in the home can avoid buying a kWh at the retail rate, while an exported kWh earns only the applicable retailer buy-back rate. A higher self-consumption share can therefore improve the result when the retail rate is higher.
Where can I find estimated annual solar generation?
Use a site-specific installer assessment that considers location, roof direction, tilt, shading and system design. The calculator does not estimate sunlight or system output from an address.
Does the calculator include a home battery?
No. Enter generation and self-consumption assumptions that reflect the system being assessed, but model battery purchase, replacement, losses and financing separately.
Are solar export rates fixed in New Zealand?
No. Buy-back rates and terms depend on the electricity retailer and plan and can change. Use the rate available to the household rather than assuming the example value will apply.
Is the projected return guaranteed?
No. Generation, equipment performance, electricity prices, export rates, maintenance and household use can all differ from the assumptions. Obtain quotes and test conservative scenarios before deciding.
Is solar power worth it in New Zealand?
It depends on the installed price, site-specific generation, how much solar electricity the household uses directly, available export rates and future costs. Enter a quote and conservative assumptions rather than relying on one general payback claim.
What is a good solar panel payback period?
There is no universal target. Compare the modelled payback with equipment warranties, expected component life, financing costs, alternative uses of the money and the uncertainty in generation and future electricity prices.