Independent research guide
Estimate solar value from electricity use, local utility rates, and PVWatts production instead of relying on a national average alone.
Last updated: Oct 8, 2026
6 min readPrimary sources linked belowSolar pricing headlines are useful for orientation, but they cannot predict the value of panels on a particular home. Two identical arrays can produce different savings because sunlight, roof geometry, electricity prices, export credits, equipment choices, and financing terms vary by address.
This guide builds a transparent estimate from official U.S. Energy Information Administration data and NREL's PVWatts model. The goal is not a precise-looking promise. It is a calculation you can reproduce, challenge, and update when a proposal or utility rule changes.
Collect at least twelve consecutive utility bills and record kilowatt-hours, not only dollars. Monthly usage reveals seasonal peaks that an annual total hides. If the household recently added an electric vehicle, heat pump, pool, or addition, model a second scenario with the expected demand.
EIA reported a 2025 U.S. residential average of 17.30 cents per kWh. That benchmark is useful, but an estimate should use the household's rate structure. Fixed customer charges, tiers, demand charges, and time-of-use periods can all affect the amount solar generation avoids.
PVWatts estimates energy output for a grid-connected photovoltaic system using location, size, equipment, tilt, azimuth, and losses. Its defaults are a starting point. Replace them with the proposed design and review whether the weather file and shading assumptions fit the site.
Start with system design, then production, then price. A lower total price can describe a smaller system, while a higher quote may include a larger array, roof work, electrical upgrades, batteries, or a different warranty. Normalize proposals before comparing dollars.
| Quote field | What to record | Why it matters |
|---|---|---|
| System size | DC kW and AC inverter capacity | Sets the scale of expected production |
| Equipment | Panel, inverter, optimizer, battery models | Affects output, warranty, and replacement |
| Production | First-year kWh and assumptions | Drives the savings claim |
| Price | Cash price and financed total | Separates equipment value from financing |
| Scope | Permits, interconnection, roof, electrical work | Reveals exclusions and change-order risk |
System capacity is stated in DC kilowatts, while the utility bill measures energy in kWh. A 6 kW array does not produce 6 kWh every hour. Output rises and falls with sunlight, temperature, orientation, shading, equipment behavior, and downtime.
Enter the project address and actual proposed design in PVWatts. Save monthly output as well as the annual total. Monthly data helps reveal whether production aligns with summer air-conditioning, winter heating, or a time-of-use tariff.
Review total losses. NREL's documented default is 14%, covering effects such as soiling, wiring, mismatch, availability, and other system losses. If a proposal uses a materially lower number, ask for the site-specific evidence behind it.
The simplest starting formula multiplies usable generation by the avoided electricity rate. If 8,000 kWh offsets electricity worth $0.173 per kWh, first-year gross energy value is about $1,384.
That split matters. A kWh used in the home may avoid the full retail rate, while an exported kWh may receive a lower credit. Fixed monthly charges generally remain. Time-of-use tariffs can make a late-afternoon kWh more valuable than a midday export.
Simple payback divides net upfront cost by first-year savings. If net cost is $18,000 and first-year savings are $1,384, payback is roughly 13.0 years.
This is a screening result, not a full investment return. It ignores the timing of cash flows, module degradation, inverter replacement, maintenance, insurance, utility-rate changes, export-policy changes, and opportunity cost. A strong proposal shows conservative, base, and optimistic scenarios rather than one exact forecast.
Use the all-in installed cash price and confirm which permits, labor, interconnection, monitoring, and warranties are included. Compare the expected return with other uses of the money and keep an emergency reserve outside the project.
Record principal, interest rate, term, monthly payment, dealer fees, prepayment rules, and total paid. A low advertised rate can be purchased through a higher financed price. Compare the cash and financed proposals side by side using the same equipment and production.
Identify the starting payment or energy rate, annual escalator, contract term, transfer requirements, maintenance responsibility, and end-of-term options. Compare contract payments with the utility costs they are expected to replace.
Incentive eligibility depends on current law, ownership structure, tax situation, equipment, project timing, and location. Do not subtract an incentive from the quote until you have checked the official program requirements and whether you can use the benefit. A tax credit is not automatically the same as an immediate cash rebate.
Ask the installer to show gross price, each assumed incentive, and final net price on separate lines. Keep a scenario without uncertain incentives so the project remains understandable if eligibility changes.
| Assumption | Conservative | Base | Optimistic |
|---|---|---|---|
| Production | Lower output / more losses | PVWatts estimate | Installer case with support |
| Utility rates | Little or no escalation | Documented planning case | Higher escalation |
| Export value | Reduced credit | Current tariff | Retail credit where applicable |
| Repairs | Replacement allowance | Expected maintenance | Minimal out-of-pocket cost |
If the project only works under the optimistic case, the decision depends heavily on assumptions outside the homeowner's control. The conservative case exposes that risk early.
There is no universal cutoff. Compare payback with equipment life, warranties, financing, moving plans, risk tolerance, and alternative uses of the capital.
No. It is a screening model and an excellent independent checkpoint. Final design requires site inspection, engineering, equipment selection, utility rules, and permitting.
Compare utility escalation, export credits, degradation, financing, incentives, and fixed charges. Small annual assumptions compounded over many years can create a large difference.
Not automatically. Roof limits, future loads, export compensation, time-of-use rates, and utility sizing rules can make a smaller or larger system more sensible.
Start with bills, model the actual address, apply the real tariff, and separate system performance from financing. A transparent base case makes proposals comparable and shows exactly which assumptions drive the result. Recalculate whenever the design, price, tariff, or incentive changes.
Quick reference
| Data point | Value | Context |
|---|---|---|
| 2025 U.S. residential electricity price | 17.30¢/kWh | Annual average, preliminary EIA data |
| 2025 U.S. all-sector electricity price | 13.63¢/kWh | Annual average, preliminary EIA data |
| Highest 2025 state all-sector average | 35.72¢/kWh | Hawaii |
| Lowest 2025 state all-sector average | 8.20¢/kWh | North Dakota |
| PVWatts default system size | 4 kW DC | Documented preliminary-analysis default |
Research
| PVWatts default system losses | 14% | Documented default loss assumption |