Estimate rooftop solar production by location with PVWatts. Adjust system size, tilt, orientation and losses, then review monthly output and model limitations.
Quick answer
PVWatts estimates AC energy from weather, array size, orientation, tilt, losses and inverter assumptions.
Notes updated 2026-10-06
Best for
Homeowners pressure-testing solar proposals before signing.
Inputs needed
electric usage, local rate, system size or quote assumptions
Formula used
PVWatts estimates AC energy from weather, array size, orientation, tilt, losses and inverter assumptions.
Method references
NREL PVWatts production model
Author profile: Marcus Vance . Read the methodology and recheck local tariff, quote, and incentive details before deciding. Attribution is not a record of independent technical review.
We geocode your address and query NREL PVWatts for your roof’s exact sun data.
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Wattcrunch Solar Planning Report
Generated 10/25/2026 · Verify assumptions with your utility and installer.
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What does an address-based production estimate measure?
Geocoding identifies a location for weather and production modeling. PVWatts then uses array size, tilt, orientation and loss assumptions. The result is a planning estimate rather than an inspection of the roof.
What should the installer confirm?
Verify usable roof area, shade, structural suitability, setbacks, equipment, interconnection and the final production model. Compare monthly modeled output with actual operating data after installation.
Can an address-based solar calculator inspect my roof?
Not by geocoding alone. An address locates the weather model; array size, tilt, direction and losses still need appropriate inputs. PVWatts estimates energy, not roof structure, exact shade, usable area or permission to connect.
What changes when the assumed annual AC production ratio changes?
Assumed annual AC yield
8 kW annual output
Interpretation
1,100 kWh/kW/year
8,800 kWh/year
Sensitivity input, not an address prediction
1,400 kWh/kW/year
11,200 kWh/year
Sensitivity input, not an address prediction
1,700 kWh/kW/year
13,600 kWh/year
Sensitivity input, not an address prediction
Illustrative assumptions: 8 kW DC array. These three yields are illustrative sensitivity inputs, not PVWatts responses for specific addresses. Actual modeled monthly output requires a successful location/weather request and disclosed array settings.
What to check on your bill or installer proposal
Match the proposed DC system size, tilt and azimuth to the installer design.
Keep modeled weather variation separate from measured roof shading.
Ask for an annual production guarantee and exclusions; a model result is not a warranty.
Example and calculation notes updated . Method references are listed below; example rates are not verified utility tariffs.
How does this solar potential estimate work?
PVWatts estimates AC energy from weather, array size, orientation, tilt, losses and inverter assumptions.
A worked example with explicit assumptions
If a location model returns 1,400 kWh/kW/year, an 8 kW array implies 11,200 kWh/year under those settings. Changing shade or orientation requires a new production estimate.
What should I verify before using the result?
Geocoding finds a location, not usable roof area. Weather-model output is not a production guarantee or a shade survey.
Use your bill or written equipment quote, run a conservative scenario, and compare the result with the same inputs in another model.
Planning notes updated October 12, 2026. Example assumptions are not a local tariff.
Pressure-test the estimate
Treat the result as a planning range, not a promise. Re-run it with a lower and higher production estimate, your actual utility tariff, and the written installer quote.
Check roof shade, orientation, tilt, and equipment losses.
Separate cash price, financing fees, battery cost, and roof work.
Verify export credits, fixed charges, and interconnection rules.
Confirm incentive eligibility, deadlines, and tax treatment.
Sources behind this estimate
Use the method references below to check the formula and its limitations. Input defaults and illustrative scenarios are not current tariffs, guaranteed output or live installer quotes.
Utility export rates, eligibility rules, and installer pricing can change. Confirm the applicable tariff, interconnection requirements, and tax treatment before making a purchase decision.
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Frequently asked questions
Does an address estimate know the exact shade on my roof?+
No. Geocoding locates the property and PVWatts models production from weather and array inputs. It does not establish usable roof area, structural condition or exact obstructions. Compare tilt, azimuth and loss assumptions with an installer roof survey.
How do I use the solar potential calculator?+
Start with your actual usage, equipment or quote inputs, keep the displayed units, and change one assumption at a time. Geocoding finds a location, not usable roof area. Weather-model output is not a production guarantee or a shade survey.
What calculation does this tool use?+
PVWatts estimates AC energy from weather, array size, orientation, tilt, losses and inverter assumptions.
Can I check the arithmetic with an example?+
If a location model returns 1,400 kWh/kW/year, an 8 kW array implies 11,200 kWh/year under those settings. Changing shade or orientation requires a new production estimate.
What could change the accuracy of my result?+
Geocoding finds a location, not usable roof area. Weather-model output is not a production guarantee or a shade survey.
Can I use the estimate outside the United States?+
Physical kW and kWh calculations use the same units internationally. Dollar results, regional defaults, emissions factors, incentives and utility guidance are US-oriented. Replace rate and production assumptions with local values; do not apply US tax or export rules abroad.
Can I print or save results without registering?+
Use Print / PDF to save this page from your browser without an email address. The solar plan stores supported scenario inputs in your browser; private files should be checked and redacted before uploading for extraction.
Compare the decision, not just the number
Compare cash, loan, lease, and battery scenarios using the same production, rate, and quote assumptions before choosing a financing path.