Solar installation
Solar installation supplied energy payback
Compare a supplied solar quote with separately entered self-used and exported energy values.
Your inputs
Complete the fields for your selected method. Zero means intentionally zero, not unknown. Currency selection labels amounts; it does not convert exchange rates.
How this calculation works
annual net value = self-used kWh × avoided price + exported kWh × credit - maintenance; simple payback = net installed cost/annual net value
Generation and self-use are supplied scenarios, not a roof or production model. Fixed utility charges are not avoided automatically. Export terms, tariff changes, degradation, finance, batteries, replacement, incentives eligibility and discounting are excluded. No electrical design or guaranteed savings. Use your own records for the same scope and period. Example figures are illustrative, not industry benchmarks. Results exclude income taxes and any cost you have not entered. Check the result before pricing work or committing resources.
What information do I need?
Use records for the same job, equipment or accounting period. Only the fields for your selected entry method are required. An unknown amount is not zero.
Input definitions and where to find them
- Net installed cost after already-confirmed credits (selected currency): Use a supplier quote, invoice, payroll record or allocated cost for the exact job or period named here. Include this amount only once.
- Supplied annual AC generation estimate (kWh/year): Use the matching measured quantity, time log, schedule or clearly stated estimate. Zero means intentionally none; an unknown amount is not zero.
- Share of generated energy used on site (%): Enter a percentage from your records or an explicitly chosen scenario. No typical or recommended rate is supplied.
- Actually avoided import cost per self-used kWh (selected currency): Use a supplier quote, invoice, payroll record or allocated cost for the exact job or period named here. Include this amount only once.
- Actual export credit per exported kWh (selected currency): Use a supplier quote, invoice, payroll record or allocated cost for the exact job or period named here. Include this amount only once.
- Annual maintenance and other operating cost (selected currency): Use a supplier quote, invoice, payroll record or allocated cost for the exact job or period named here. Include this amount only once.
Use the Where to find this value controls beside the inputs for available work-it-out helpers. Estimates remain your assumptions; a helper does not verify the source figures.
Worked example
Example amounts use US dollars (USD).
Example answer: Modeled first-year net energy value is $1,050.00 for the illustrative inputs below.
Example inputs
- Net installed cost after already-confirmed credits: $15,000.00
- Supplied annual AC generation estimate: 10,000.00 kWh/year
- Share of generated energy used on site: 70.00 %
- Actually avoided import cost per self-used kWh: $0.15
- Actual export credit per exported kWh: $0.05
- Annual maintenance and other operating cost: $150.00
- Modeled first-year net energy value
- $1,050.00
- Simple payback at constant annual value
- 14.29 years
- Self-used energy
- 7,000.00 kWh/year
- Exported energy
- 3,000.00 kWh/year
These illustrative values are not recommended rates or industry averages. Replace every example input with your own figures.
Use the result well
Compare a supplied solar quote with separately entered self-used and exported energy values. Inputs come from your own records and stated assumptions; no rates or legal limits are looked up.
Keep inputs on the same scope and time basis. Calculations retain precision internally; displayed values generally round to two decimal places, with extra precision for very small values and whole-unit rounding where required. Economic comparisons describe your supplied assumptions and do not guarantee future results.
This tool provides business arithmetic. It does not approve engineering designs, establish legal or tax treatment, select equipment or certify safe operating conditions.