Offline
No internet, no account required.
NREL
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact NREL reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
A solar quote only sells if the customer sees the payback. This app turns system cost, incentives, and energy savings into the numbers buyers ask for: simple payback, return on investment, and lifetime savings.
What it computes
- Net cost after the federal tax credit and any local rebates.
- Annual savings from offset electricity at the local rate (with optional rate escalation).
- Simple payback = net cost ÷ annual savings, plus 25-year cumulative savings.
Worked example
A $24,000 system with a 30% credit nets $16,800. If it saves $2,100/year, simple payback = 16,800 ÷ 2,100 = 8 years, with two decades of savings after that.
Related calculators
Estimate the savings input with the production estimate calculator after sizing with the panel sizing calculator.
Solar ROI FAQ
What is simple payback?
It is the net system cost divided by the annual energy savings — the number of years until the system has paid for itself. It is the figure most homeowners ask for first.
Does it include incentives?
Yes. You can enter the federal tax credit and local rebates so the payback is based on net cost, not sticker price.
Can it model rising rates?
Yes. An optional utility rate escalation increases annual savings over time, which shortens payback and raises lifetime savings.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Solar Roi Calculator on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.