BISOL, which describes itself as Europe's largest premium solar module manufacturer, began offering an enhanced warranty on its standard modules from 1 August 20251. The company announced the change in posts published on 18 September 2025 in French, English and German1.
The new terms cover a 30 year power output guarantee, linear to 90 per cent, and a 25 year product guarantee1. BISOL states that its modules show only 0.01 per cent degradation after 20 years, which it describes as verified real world performance rather than a laboratory projection1. The announcement also lists hail resistance of 40 mm diameter at 99.1 km/h, certified HW4, snow load up to 11,000 Pa on the BSO series, wind load of 2,400 Pa, three bypass diodes and MC4 compatible connectors1. The modules are described as 100 per cent designed and manufactured in the EU1.
"As of 1 August 2025, BISOL ® offers an upgraded warranty that sets a new benchmark for performance and trust in the solar industry."
The warranty applies to all standard BISOL modules, including the BDO, BBO and BSO ranges, to all new orders, and is globally applicable1. BISOL says it is already included in all updated datasheets and price lists1. The company states that the new guarantee applies only to standard modules, and that its BISOL Supreme range continues to carry what it calls the world's only 100 per cent power output guarantee for 25 years, without degradation1.
| Item | New standard module warranty |
|---|---|
| Power output guarantee | 30 years, linear to 90%1 |
| Product guarantee | 25 years1 |
| Stated degradation after 20 years | 0.01%1 |
| Hail resistance | 40 mm at 99.1 km/h, HW4 certified1 |
| Snow load | up to 11,000 Pa (BSO series)1 |
| Wind load | 2,400 Pa1 |
BISOL says its products operate in more than 120 countries and are manufactured under full internal control with no outsourcing1. The company claims more than 20 years of real world results and one of the lowest complaint rates in the industry1. No independent verification of the degradation figure or the complaint rate is given in the announcements, and no UK-specific pricing or availability has been reported.
Why it matters for households
A module's warranty length and its degradation rate determine how much of a system's original output is contractually promised over the decades a roof array is expected to work. A 30 year power guarantee linear to 90 per cent means the manufacturer commits to the panel still producing at least 90 per cent of its rated output at the end of that period, with the decline spread evenly rather than stepped1. The separate 25 year product guarantee covers defects in the panel itself rather than its output1.
For a household, the practical effect sits in the difference between the two figures. Output guarantees are common across the industry; product guarantees of this length are less so, and the split between them is what determines whether a fault in year 20 is a warranty claim or a replacement cost. The claimed 0.01 per cent degradation after 20 years, if it holds, would be far below the annual decline assumed in most performance estimates, though the figure comes from the manufacturer's own installations and has not been independently reported1.
Because the warranty applies to all new orders and is globally applicable, a UK household buying a standard BISOL module after 1 August 2025 would fall under the new terms, with the paperwork already reflected in updated datasheets and price lists1. The BISOL Supreme range sits outside this change and keeps its existing terms1.
What happens next
The warranty applies to new orders placed from 1 August 20251. No end date for the offer, and no UK-specific terms, have been reported.
Sources3 cited
- Post | BISOL, bisol.com
- The best solar guarantee. Now standard at BISOL, bisol.com
- Post | BISOL, bisol.com