Off-grid solar system for an office — a LONGi array of 18 × 550 W

The count comes from the energy, not from the roof. Added up, the appliances of this profile draw close to 40.4 kWh in twenty-four hours; the sizing assumes 5.7 hours of peak sun, which puts the array at 9.5 kWp. The calculator then takes the LONGi listing nearest 550 W, the Hi-MO X10 Guardian LR7-60HVHL 550W, and rounds up: 18 × 550 W is 9.9 kWp.

The Hi-MO X10 Guardian LR7-60HVHL at 550 W converts 24.4% of the light on its face and measures 1990 × 1134 × 30 mm — 244 W for each square metre of module. At 16.3 kg it loads the roof with 7.2 kg per m², the lowest figure of any module in this catalogue. The front is single glass, 1.6mm coated semi-tempered glass.

Side by side, the 18 modules are 40.6 m² of glass; their 293 kg is counted without rails or clamps. The 47 m² this page shows is larger because it is the sizing's allowance per module, not the glass itself. The record rates each module for 3,600 Pa of static load on its front and 2,400 Pa on its rear, and its hail test reads: 25mm Hailstone at the speed of 23m/s.

Electrically, a string gains 45.08 V of open-circuit voltage with every module, and 37.31 V once the modules work at full power, where each carries 14.74 A (15.45 A short-circuit). Wired as two strings of 9, the array stands at 405.7 V open-circuit and works at 335.8 V per string. The module itself sets a limit of 1500 V of system voltage, with a 25 A series fuse — 33 modules in a string at test conditions; open-circuit voltage climbs 0.2% for every °C the cells cool below 25 °C. The inverter chosen for the kit sets a tighter limit, and its DC window is the one the strings must fit.

On a hot roof, read the power coefficient first: this module's record gives -0.26%/°C. Ten degrees of cell temperature above the 25 °C test point take 2.6% off the rating — about 0.26 kW across this array. The record's nominal operating cell temperature is 45±2°C.

The inverter line reads 10 kW: with the motors of this profile starting together, the draw peaks at 9.2 kW. The storage line reads 41 kWh: a full day of use with a reserve for a day without sun comes to about 40.4 kWh. Both are sizes to buy against, not LONGi products: what can be ordered on this page is the modules.