You want the bottom line: How fast does solar pay for itself?
This page explains the logic behind the Solar ROI Calculator, what each input means, and how to read the results—without turning it into a math class.
What this calculator does (in plain English)
- Estimates payback period (years until your solar system “breaks even”).
- Projects lifetime savings vs staying on the grid.
- Lets you model loans vs cash, and with/without batteries.
- Adapts to your actual bill and local rates.
If you just want to try it, jump in here: Open the Solar ROI Calculator.
Inputs (the knobs you can turn)
- Average monthly bill ($): Your real monthly electricity spend.
- Grid rate ($/kWh): Your current price per kWh (with fees).
- System size (kW): Planned array size (or use our preset suggestions).
- Installed cost ($): Total project cost (before/after incentives—your call).
- Battery (optional): Add capacity to see how it affects payback.
- Financing: Cash vs loan (enter rate & term if using a loan).
- Annual bill increase (%): Utilities rarely go down. Model reality.
> Not sure what’s eating your power? Check our Appliance Cost Calculator to see the real hogs.
How the math flows (short version)
- Annual Grid Cost Today = monthly bill × 12
- Solar Production Value = (system kW × local yield) × grid rate
- Annual Savings ≈ current grid cost − (post-solar grid cost)
- Payback (years) = installed cost ÷ annual savings
- ROI grows as grid prices rise and your loan (if any) is paid down.
The calculator handles the messy bits (fees, bill growth, battery effect) so you can compare apples to apples.
Quick example
- Monthly bill: $250 → Yearly: $3,000
- Installed cost: $18,000
- Modeled annual savings: $3,000 (conservative, no rate hikes)
- Payback ≈ 6 years. After that, you’re largely just riding sunlight.
Run your own numbers here: Solar ROI Calculator.
Cash vs Loan (what changes)
- Cash: Highest upfront, fastest long-term gain.
- Loan: Smaller upfront; monthly loan payment can be lower than your old bill. Payback extends slightly but stays attractive if rates keep rising.
Tip: Compare 10–20 year totals, not just month-to-month.
Batteries: worth it?
Batteries add resilience (outages) and can speed savings if your utility has high evening rates. They also add cost. Use our Battery Sizing Calculator to pick a right-sized pack, then recheck ROI here.
Common questions (fast answers)
- Will shading ruin ROI? It hurts production. Size accordingly or trim trees.
- Move soon? Payback needs time. If you’ll sell soon, solar can still add resale value.
- Maintenance? Panels: rinse occasionally. Inverters: eventual replacement. Batteries: follow warranty cycle life.
Troubleshooting your inputs
- Bill fluctuates? Use a 12-month average.
- Don’t know grid rate? Divide a bill’s total charge by kWh used on that bill.
- Incentives? Subtract them from installed cost for a “net” scenario; save a copy with “gross” too.
What to do next
- Get your baseline: Run ROI.
- Find the leaks: Appliance Cost Calculator.
- Add resilience: Battery Sizing Calculator.
- Then decide: cash, loan, or wait.