Solar Electricity
Solar Payback Calculator
Use Solar Payback when simple payback is the quantity you need. Enter installed cost and annual savings, then compare the answer with the equipment or operating limits that apply to your case.
Set up the Solar Payback case
Check the source and units before calculating.
Input notes
Use site-specific irradiance, temperature, shading, and equipment data. Do not combine a worst-case value with unrelated nominal data.
Values used below a division bar must stay positive. Convert units once, retain the original reading, and verify the converted magnitude. If you also need annual energy savings, continue with Energy Efficiency Savings Calculator.
- Installed cost
- Default example: 14000 $. Enter installed cost in $.
- Annual savings
- Default example: 1600 $/year. Enter annual savings in $/year.
Common entry mistakes
Values recorded at different operating points should not share one case.
Verify sign, scale, and physical meaning before accepting the number.
Formula used on this page
Here, Simple payback is obtained from payback = cost ÷ annual savings. Only Installed cost and Annual savings enter the numerical result.
For the example shown, simple payback equals 8.75 years. Treat that value as a demonstration, not a recommendation.
Calculate simple payback from installed cost and annual savings. Another relevant worksheet is Off-Grid Solar Array Calculator.
Applying the result
Use Simple payback as one quantified check within the larger decision. Compare it with module, inverter, controller, and storage ratings.
Keep the input set beside the output so another reader can reproduce it.
Changing Installed cost
Change Installed cost from 14000 $ to 16800 $ with every other entry unchanged. The result changes from 8.75 years to 10.50 years.
Keep both cases when the changed input represents genuine uncertainty.
Assumptions and limitations
Financing, maintenance, degradation, and tariff changes are omitted.
Further engineering review can cover seasonal resource variation and controller or inverter operating windows. Test an additional scenario when an omitted effect has a plausible range.
Base energy estimates on the limiting season rather than an annual average alone.
A final reasonableness check
Review annual savings and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.
Use simple payback alongside a monthly or seasonal production case. Preserve the unrounded number until all dependent calculations and comparisons are complete.
Document any effect handled outside this page, especially seasonal resource variation and controller or inverter operating windows. That note prevents a later reader from assuming the simple equation covered it.
Before relying on the answer
How do I run a useful sensitivity check?
Use separate labeled cases when more than one condition changes. Use site-specific irradiance, temperature, shading, and equipment data.
Does the answer include a design margin?
No. Compare the value with a monthly or seasonal production case and apply relevant equipment and installation requirements.