Compare the total cash price
An installed price per watt makes quotes easier to compare only when both quotes include the same scope. Divide the complete cash price by the DC panel capacity in watts. A 6 kW system quoted at $18,000 is $3.00/W. A lower advertised price can exclude panel removal, roof repairs, electrical upgrades or permitting.
Ask for an itemized quote
| Item | What to check |
|---|---|
| Panels and inverter | Exact model, DC capacity, AC output, warranties and expected degradation. |
| Installation and mounting | Roof penetrations, flashing, structural checks and workmanship coverage. |
| Permits and interconnection | Who obtains approvals, included fees and expected permission-to-operate process. |
| Electrical upgrades | Main panel, meter, wiring and service changes included or excluded. |
| Battery and backup | Usable kWh, continuous/peak kW, backup circuits and any transfer equipment. |
| Production estimate | Address, orientation, shade assumptions and first-year annual kWh. |
Cash, loans, leases and PPAs
A financed quote can have dealer fees, interest or a higher equipment price. Compare total payments and any early repayment terms, not just the monthly payment. For a lease or power purchase agreement, examine escalation, minimum payments, maintenance obligations, buyout terms and what happens when you sell the property.
Solar Panel Calculator estimates cash ownership. It does not calculate a loan amortization schedule or a PPA bill. Entering a loan’s monthly payment as an electric bill produces a misleading result.
Include lifetime ownership costs
Inverter replacement, battery replacement and service visits can change net savings. A product warranty is not a guarantee that every labor or transportation cost is covered. Ask which failures are covered, who performs service and whether you must pay diagnostic or removal fees.
A consistent comparison
- Collect 12 months of household usage and charges.
- Get at least two itemized proposals using the same expected production target.
- Use your utility’s actual self-use and export terms.
- Compare gross bill savings with the full upfront and lifetime cost.
- Repeat with lower production and higher repair costs before committing.
Sources and verification
- EIA Electric Power Monthly: electricity prices
- PVWatts: location-specific solar production estimates
- IRS: Residential Clean Energy Credit
Links provide primary references or verification tools. Linking a source does not mean every calculator default is reproduced from it. See our data limitations.