Solar Payback Calculator
Estimate annual solar generation, self-consumption savings, export value, simple payback and long-term net benefit using fully editable assumptions.
Default project preview
11.7 years
Net system cost
$16,000.00
On-site generation
6,720 kWh
Exported generation
4,480 kWh
First-year gross value
$1,523.20
Calculator
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Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Solar system size
Enter this project assumption in kW. The current imperial default is 8 kW.
Annual yield per kW
Enter this project assumption in kWh/kW. The current imperial default is 1400 kWh/kW.
Generation used on site
Enter this project assumption in %. The current imperial default is 60 %. Minimum: 0. Maximum: 100.
Avoided electricity price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
Export credit
Enter this project assumption in per kWh. The current imperial default is 0.07 per kWh. Minimum: 0.
Installed system cost
Enter this project assumption in a unitless value. The current imperial default is 18000. Minimum: 0.
Incentives or rebates
Enter this project assumption in a unitless value. The current imperial default is 2000. Minimum: 0.
Annual maintenance
Enter this project assumption in a unitless value. The current imperial default is 150. Minimum: 0.
Analysis period
Enter this project assumption in years. The current imperial default is 25 years. Minimum: 1. Maximum: 40.
Annual production degradation
Enter this project assumption in %. The current imperial default is 0.5 %. Minimum: 0. Maximum: 5.
How to read the outputs
Net system cost
cost minus entered incentives. Default preview: $16,000.00.
On-site generation
avoided retail purchases. Default preview: 6,720 kWh.
Exported generation
credited at export rate. Default preview: 4,480 kWh.
First-year gross value
self-use plus exports. Default preview: $1,523.20.
First-year net benefit
after maintenance. Default preview: $1,373.20.
25-year net benefit
0.5% annual degradation. Default preview: $16,130.43.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Annual generation = system size × annual yield. Annual value = self-used energy × retail price + exports × export credit − maintenance. Simple payback = net installed cost ÷ first-year net benefit.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: August 19, 2026
Estimate first-year solar generation, self-consumption savings, export value, simple payback and long-term net benefit from editable yield, tariff and degradation assumptions.
Calculation steps
- 1Multiply system kW by site-specific annual yield per kW.
- 2Split generation into self-consumed and exported energy.
- 3Value self-consumed kWh at avoided retail price and exports at the entered credit.
- 4Subtract annual maintenance and compare first-year benefit with installed cost net of incentives.
Worked numerical example
An 8 kW system at 1,400 kWh/kW-year produces about 11,200 kWh in year one. If 60% offsets 0.18/kWh electricity and 40% earns 0.07/kWh export credit, gross energy value is about 1,523 before the entered annual maintenance cost.
Purchasing and rounding
Use actual installer production estimates, equipment warranties, tariff rules and incentive eligibility. Simple payback excludes financing, tax treatment and future tariff escalation unless modeled separately.
Interpret the result
Simple payback is a screening metric, not an investment guarantee. Long-term value is sensitive to production degradation, self-consumption and future electricity/export prices.
Page-specific assumptions
- Annual yield is appropriate for the site.
- Self-consumption percentage remains representative.
- Entered prices and maintenance are real planning assumptions.
Common mistakes
- Valuing exported energy at the full retail rate when the tariff pays less.
- Ignoring shading or orientation in annual yield.
- Treating simple payback as discounted cash-flow analysis.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Solar Payback Calculator questions
Is annual solar yield the same everywhere?+
No. Solar resource, orientation, tilt, shade, temperature and system losses all affect production.
Why separate self-consumption and exports?+
Energy used on site may offset a different price than energy exported to the grid.
Does simple payback include financing?+
No. Loan interest, discount rate, taxes and cash-flow timing require a more detailed financial model.