Solar Resource Peak Sun Hours Chart

Use this chart to document the solar-resource basis behind a calculator result or PV production estimate: NREL PVWatts results, NSRDB or weather-data notes, peak sun hours, tilt, azimuth, date retrieved, seasonal basis, shading notes, and the production model that still needs verification.

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Quick reference table

A peak sun hours chart is an estimation worksheet: peak sun hours x system kWdc estimates daily kWh before losses. Record NREL PVWatts or NSRDB source data, tilt, azimuth, date retrieved, annual kWh, and seasonal assumptions before system sizing or ROI review.

Solar resource worksheet

Solar resource worksheet
Item	Record on worksheet	Why it matters
Location basis	Address, ZIP code, latitude/longitude, or station note	Solar resource varies by site and weather dataset
Resource source	NREL PVWatts, NSRDB, installer model, or user-entered value	The worksheet must show where peak sun hours came from
Array geometry	Tilt, azimuth, array type, and shade note	Geometry changes useful irradiance and seasonal output
Review date	Weather data year or dataset, date retrieved, reviewer	Resource data and project assumptions can change over time

Peak sun hours documentation

Peak sun hours documentation
Use case	Worksheet field	Boundary
System sizing	Peak sun hours, losses, performance ratio	Use as an early estimate before site-specific modeling
Row spacing	Tilt, latitude, seasonal sun angle note	Do not mix annual production tilt with winter shadow geometry without labeling it
ROI and emissions	Annual kWh source, date retrieved, degradation note	Financial and carbon worksheets need the production basis visible
Proposal review	PVWatts or model file, weather dataset, shade note	Use the worksheet before final engineering and production modeling

When to use the solar sizing calculator

When to use the solar sizing calculator
Use case	Open the calculator when	Keep on this chart
Peak sun hours lookup	You need to turn a documented resource value into daily or annual kWh	Resource source, date retrieved, and weather dataset
PVWatts production estimate	You have DC size, losses, tilt, and azimuth ready for a system-sizing run	PVWatts assumptions and model limitations
Row-spacing review	Tilt or seasonal sun angle changes the array layout decision	Tilt, azimuth, seasonal basis, and shade note
ROI or emissions review	Annual kWh needs to feed finance, carbon, or owner review	Selected production basis and date retrieved

Formula basis

Estimated daily kWh = system kWdc x peak sun hours x performance ratio. Annual kWh should be checked against NREL PVWatts or another documented production model before proposal use.

Peak sun hours is the equivalent full-sun resource used for an early estimate, not an assured production result.
NREL PVWatts records site location, selected weather data, tilt, azimuth, DC size, losses, DC/AC ratio, and inverter assumptions.
NSRDB identifies the solar radiation and meteorological dataset behind many U.S. solar-resource workflows.
Tilt is the array angle from horizontal and should match roof, rack, or design assumptions.
Azimuth records the array compass direction and helps explain production differences between south-, east-, and west-facing arrays.
Date retrieved records when the PVWatts, NSRDB, or other solar-resource value was retrieved or approved.

Worked examples

Residential PVWatts source recordRecord the address or ZIP, PVWatts run date, selected weather dataset, tilt, azimuth, losses, peak sun hours basis, first-year kWh, and whether shade modeling is still pending.

Ground-mount tilt comparisonDocument candidate tilt, azimuth, seasonal resource basis, row-spacing note, peak sun hours, PVWatts annual kWh, and review notes before moving to array sizing.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The worksheet is an estimating reference and does not guarantee production, utility approval, interconnection approval, or financial performance.
Non-U.S. regional resource tables and archived rows are not used as U.S. public defaults.
Peak sun hours should be user-entered or documented from a current documented workflow such as NREL PVWatts, NSRDB, or an installer model.
Tilt, azimuth, shading, soiling, temperature, inverter clipping, snow, and seasonal weather can all change actual production.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart to document source data and assumptions; verify NREL PVWatts inputs, weather dataset, date retrieved, address, tilt, azimuth, array type, losses, shade model, equipment assumptions, site-specific production model, interconnection requirements, and project review before relying on production values.

How to use this chart

1Record the resource sourceWrite whether the value came from NREL PVWatts, NSRDB, an installer model, a measured source, or a user-entered planning assumption.

2Attach array geometryRecord tilt, azimuth, array type, shade note, loss basis, and whether the value is annual, seasonal, or monthly.

3Route production reviewCarry the date retrieved and resource notes into system sizing, ROI, emissions, and project review.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Capture location and sourceRecord address or ZIP, weather dataset, date retrieved, PVWatts or model run, and reviewer.
Capture geometry and lossesWrite tilt, azimuth, array type, shade, soiling, temperature, inverter, wiring, and availability assumptions.
Record next stepDocument peak sun hours, annual kWh, seasonal note, production-model status, and next calculator or worksheet.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Using archived non-U.S. regional resource rows as U.S. defaults.
Treating peak sun hours as a production guarantee instead of an estimating input.
Comparing tilt cases without recording azimuth, shade, date retrieved, weather data, and seasonal boundary.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Is peak sun hours the same as expected daily production?

No. Peak sun hours is an early estimating input that compresses solar resource into an equivalent full-sun value. Weather, shade, tilt, azimuth, soiling, temperature, inverter clipping, and equipment availability can change actual production.

Should I use PVWatts or a simple peak sun hours estimate?

Use peak sun hours for early sizing estimates. Use NREL PVWatts, NSRDB-backed data, or a site-specific model before a proposal, finance case, or published production estimate.

When should I open the solar sizing calculator from this chart?

Open the calculator when the chart has a documented date retrieved, peak sun hours or PVWatts basis, tilt, azimuth, and loss assumptions ready to convert into daily or annual kWh.