Solar panels and panel brands

How Big Is a 400W Solar Panel, and How Many Fit on a Roof?

Published September 23, 2026 · By the SolarPanelX editors · Prices and specs as of that date, from the pages under Sources

Summary

Qcells' Q.PEAK DUO BLK ML-G10+ in its 400 W class measures 1,879 × 1,045 mm, about 1.96 m², and weighs 22.0 kg. An 8 kW system built from it takes 20 panels and roughly 39 m² of module area. Panels of nearly the same size can carry more watts, and Qcells' Q.TRON BLK M-G2+ reaches 440 W on 1,722 × 1,134 mm.

Watts per square meter

Model	Rating	Dimensions	Area	Per m²	Weight
Qcells Q.PEAK DUO BLK ML-G10+	400 W	1,879 × 1,045 × 32 mm	about 1.96 m²	about 204 W	22.0 kg
Qcells Q.TRON BLK M-G2+	440 W	1,722 × 1,134 × 30 mm	about 1.95 m²	about 225 W	21.2 kg

Both rows come from Qcells datasheets dated April 2026. Building 8 kW from 440 W Q.TRON modules takes 19 panels (8.36 kW) and about 37 m², some 2 m² less than twenty 400 W Q.PEAKs. A roof that is not a clean rectangle can fit fewer panels than its area suggests.

The Q.PEAK product page lists 395 to 415 W while its datasheet covers 395 to 420 W. We used the datasheet.

Scaled from NLR PVWatts estimates for a south-facing, 20-degree array with 14% losses, one 400 W panel averages about 1.9 kWh a day in Phoenix, 1.4 kWh in New York, and 1.2 kWh in Seattle over a year.

Sources

We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.

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