Use this guide
Choose the questions relevant to your situation. Expand each answer, save the checklist and request written clarification where evidence is missing.
Questions homeowners ask
Which capacity belongs in the estimate?
The calculator asks for system size in DC kilowatts. Keep the panel nameplate total separate from inverter AC capacity. For illustration, twenty 400-watt panels total 8 DC kW; that arithmetic does not verify the proposed equipment or wiring.
Source: PVWatts: calculator assumptions and site-input limitations. Reviewed 2026-10-06.
Does drawing an area on a roof verify the proposed array?
No. PVWatts says its roof-area size estimate does not account for tilt, azimuth or shading. Obtain the actual equipment schedule and roof evidence rather than treating the drawn area as a completed design.
Source: PVWatts: calculator assumptions and site-input limitations. Reviewed 2026-10-06.
Does the weather file describe my last billing month?
Not automatically. The V8 documentation identifies typical meteorological year datasets and the weather-source fields returned with results. Retain the dataset, location and period. A typical-year estimate is a different record from measured weather during your actual operating month.
Source: PVWatts V8: input, weather and output definitions. Reviewed 2026-10-06.
Does the default shading loss prove my roof has little shade?
No. The calculator’s default shading assumption represents little or no shading. Ask what site assessment supports the selected value. Keep a default, a remote model and a measured observation distinctly labeled.
Source: PVWatts: calculator assumptions and site-input limitations. Reviewed 2026-10-06.
Which energy output should I retain?
V8 defines monthly and annual AC energy in kWh; hourly AC output is in watts. Preserve the output label and interval. Comparing an instantaneous power reading with a monthly energy total does not answer whether the estimate was met.
Source: PVWatts V8: input, weather and output definitions. Reviewed 2026-10-06.
Can a forecast establish an equipment fault or a warranty remedy?
No. DOE explains that model uncertainty depends on inputs and the underlying representation. A difference calls for checking configuration, data and conditions. A qualified investigation and the actual warranty are separate from the forecast.
Source: DOE: photovoltaic modeling uncertainty. Reviewed 2026-10-06.
Your decision checklist
- Obtain the complete estimate and its preparation date.
- Identify actual DC capacity, inverter and roof-plane layout.
- Retain weather dataset, location and model version.
- Label tilt, orientation and loss assumptions with their evidence.
- Keep monthly AC energy and warnings with the inputs.
- Compare estimates, measured generation and bills separately.
Save or print this guide from your browser. Keep completed records privately.
Prepare the questions and separate the records
| Record | Question to resolve |
|---|---|
| Equipment and layout | Which panel total, inverter and roof planes are represented? |
| Weather basis | Which location, source and representative period support the estimate? |
| Site assumptions | Which orientation, tilt and losses have evidence, and which remain defaults? |
| Comparable output | Which month, AC energy unit and scenario does each result describe? |
| Open question | What should the designer or scoped reviewer explain before reliance? |
Start with the complete proposal estimate, not a screenshot of its annual headline. Ask the author for the input record, monthly output, model version and important warnings. Mark each input documented, estimated or unresolved. Keep the original file privately so a later revised scenario can be compared with the version used in the proposal.
Next, match the represented system to the actual proposal. Record panel quantity and model, roof planes, orientation and the intended inverter. If a reviewer combines different roof planes into one representation, ask why that method is appropriate and what limits it introduces. Do not change assumptions merely to make the result match a sales promise.
Example: two proposals show similar annual generation, but one represents a different panel total and shading assumption. Ask both authors to explain those inputs before ranking the offers. An equal headline does not establish equal equipment, site evidence or performance.
Example: a homeowner compares a typical-year monthly estimate with an app total covering only part of that month. First retain the dates, missing-data status and what the app measures. A lower partial-period total cannot by itself establish a failed array. Use qualified support for an unresolved physical concern; do not open equipment or climb onto the roof.
The benefit of this record is a reproducible question: which assumption changed and why? Its limit is that a planning estimate cannot inspect concealed conditions, certify a design, establish delivered generation or decide a guarantee. Separate a technical forecast from any written production commitment and its measurement rules.
Generation is also separate from bill savings. Keep imports, exports, household use, tariff periods, recurring charges and solar payments in the financial comparison. Do not multiply every forecast kWh by a retail rate and call that a verified household benefit.
Reviewed October 6, 2026 against the current PVWatts calculator, its V8 definitions and DOE modeling guidance. Our worksheet and hypothetical examples are editorial aids. These references do not endorse Solar Survey AI or validate an individual estimate.
Continue with roof and shade planning, bill and export-credit records and safe system-problem checks. Solar Survey AI’s evidence methodology and shading services explain relevant scope; confirm availability, input quality and limitations. For installed-system observations, confirm inspection scope, qualifications and conflicts. A third-party review is not automatically independent. Homeowner monitoring connections and planned remote diagnosis remain coming soon.
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About these guides
Published by Solar Survey AI, a commercial survey-services company. Our original decision checklists are recommendations; linked authorities support the referenced facts. We may benefit if you purchase our services. This is not independent certification of our company, a project-specific engineering decision or personal tax/legal advice. Local rules, contracts and site evidence control individual decisions. Reviewed 2026-10-06.
For available survey or inspection services, confirm your project scope and availability with our team. Our planned free homeowner remote diagnosis remains coming soon.
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