Review notes
- 24 panels × 420 W = 10,080 W DC, or 10.080 kW DC.
- The quoted system size matches the module-group nameplate calculation when both are rounded to two decimal places.
- This checker verifies module nameplate arithmetic only. It does not estimate annual kWh production, clipping, temperature effects, bifacial gain, degradation, roof losses, inverter efficiency or utility export limits.
Using module values transferred from a proposal PDF
Quote Analyzer can send this checker one or two explicit module groups when the PDF text provides panel counts and module wattages clearly enough to validate the arithmetic. The handoff contains only the numeric group values and, when available, the separately quoted DC system size. It does not transfer the proposal PDF, installer name, street address, financing or production forecast.
If the proposal appears to contain more than two distinct module groups, an unsafe combined count or only a partial second group, Home Solar Atlas withholds the arithmetic handoff rather than choosing values on the homeowner's behalf. Confirm every transferred number against the original proposal before relying on the result.
How DC system size is calculated
For a single-module model, total DC nameplate is panel count × module nameplate watts. Divide total watts by 1,000 to express the result in kW DC. For example, 24 × 420 W = 10,080 W, or 10.08 kW DC.
If the proposal uses two module wattages, enter the primary group and optional Group B separately. For example, 16 × 420 W plus 8 × 405 W equals 9,960 W, or 9.96 kW DC. The checker intentionally requires both Group B fields so a partial second group cannot silently change the calculation.
DC system size is not inverter AC capacity
Panel nameplate is measured on the DC side. Inverter continuous output is an AC rating and may be lower or higher than the module DC total. If both numbers are available, review their relationship separately rather than treating one as a typo.
Nameplate kW does not predict annual kWh by itself
Two systems with the same DC nameplate can produce different annual energy because roof direction, tilt, shade, weather, equipment behavior and modeled losses differ. Use system-size arithmetic first, then review the installer's production claim independently.
Frequently asked questions
How do I calculate a solar system's DC size from panel count?
Multiply the number of modules by each module's DC nameplate wattage, add the watt totals for any separate module groups, then divide total watts by 1,000. For a single module model, 24 panels at 420 W each equal 10,080 W DC, or 10.08 kW DC.
Can I calculate a solar proposal that uses two different panel wattages?
Yes. Enter the main panel group in Group A and the second count and wattage in Group B. The checker adds both DC nameplate totals before comparing the result with the quoted system size. Leave both Group B fields blank for a single-module array.
Can Quote Analyzer load panel-count and wattage values into this checker?
Yes, when a supported text-based proposal PDF contains one or two explicit module groups that can be reduced safely to panel count and module wattage. The handoff transfers only those validated numeric values and an optional quoted DC system size. Ambiguous module-group detections are withheld rather than guessed, and every transferred value should still be confirmed against the original proposal.
Is solar DC system size the same as inverter AC capacity?
No. Module nameplate size is a DC rating. Inverter continuous output is an AC rating, so the two values can legitimately differ. Review their relationship with a DC/AC ratio check instead of assuming one value is wrong.
Why might panel count times wattage not match the quoted system size?
Possible reasons include the wrong panel count, the wrong module wattage, an omitted mixed-module group, rounding, a proposal revision, or a number that is actually AC capacity rather than DC capacity. The mismatch is a reason to verify the written design, not proof of an installer error.
Does a matching panel-count calculation mean the solar design is correct?
No. A match confirms only the arithmetic of module counts and nameplate wattages. It does not validate roof layout, electrical design, inverter compatibility, structural engineering, annual production, utility interconnection or installer quality.
How does the checker handle rounding differences?
The checker reports the exact calculated kW and the quoted-minus-calculated difference, and it also indicates whether the two values match when rounded to two decimal places. Verify the underlying module counts and wattages whenever the proposal uses different precision.
Can I use annual solar production kWh to calculate system size?
Not with this arithmetic check. Annual kWh is an energy estimate affected by irradiance, roof direction, shade, weather and losses. System nameplate kW should be checked from module counts and module DC wattages, while production claims should be reviewed separately.