Choosing solar panels: read the exact model's datasheet
Sources checked
Compare panels using the manufacturer's datasheet for the exact model. Rated Wp, dimensions, weight, temperature coefficient, separate product and performance warranties, certification and electrical compatibility matter more than a brand or technology name.
Power, area and the number of modules
Panel count equals array power in kWp × 1,000 ÷ module power in Wp, rounded to a feasible whole-panel design. Nineteen 535 Wp modules give 10.165 kWp. A bigger wattage per module usually also means a larger module, so check the layout rather than choosing the largest headline rating.
The source's LONGi LR7-60HVH-535M example gives 535 Wp, 23.7% module efficiency, dimensions of 1,990 × 1,134 × 30 mm and a power temperature coefficient of −0.26%/°C. The older datasheet says 25.3 kg, whereas the manufacturer's later page says 24.8 kg. Confirm the delivered revision.
Electrical compatibility and test conditions
STC ratings use irradiance of 1,000 W/m² and cell temperature of 25°C. Actual output changes with light and temperature. Check open-circuit voltage and short-circuit current, together with operating voltage and current, against the inverter's string and MPPT limits, including cold conditions.
The example lists 15 years of product warranty and 30 years of linear performance warranty. Those cover different promises. Obtain the full regional terms and certificates for IEC 61215 and IEC 61730; a module certificate does not certify the whole roof installation.
Price is only part of selection
The three shop observations in the source were approximately €0.17–€0.21 per Wp including seller-displayed VAT on 21 October 2026. Delivery, mounting, inverter, protection and installation are additional parts of a system's cost.