Degradation
Modelling recommendations
In PV simulation software, an average annual degradation rate is typically needed as input.
Recommended degradation rate: In optimistic scenarios, 0.3%/year can be used as average annual degradation rate. In more neutral or conservative scenarios, we recommend using a value more in line with typical module performance warranties and large degradation studies published internationally, in the 0.5 to 0.8%/year range.
Background: State of the art & knowledge gaps
It is commonly hypothesized that degradation rates in the Nordic region are lower than in other regions. The rationale is that the Nordics experience lower irradiance, resulting in reduced UV exposure, as well as lower temperatures, both of which can reduce material degradation. This hypothesis find support in the literature published so far: While most reported degradation rates lie in the 0.5 to 0.8% per year range [1], degradation rates of 0.2% per year or lower have been found for systems installed in the Nordics [2–4]. Studies of climates similar to the Nordics internationally report degradation rates between 0.2 and 0.4% per year [5].
However, the sample size in existing studies is still small, and the analyzed time-series are short. Further, degradation is highly dependent on PV module design and bill of materials, which is evolving at a fast and accelerating pace. The resulting impacts on degradation are expected to vary across climates. An example is multiple recent trends that significantly change the module mechanical characteristics [6]. This creates uncertainties in mechanical reliability, which is potentially exacerbated by snow and ice loading experienced in a Nordic climate. These effects are so far not well understood and require further research.
ReFERENCES
[1] H. Hieslmair et al., DNV’s views on long-term degradation of PV systems, DNV Whitepaper, 2024.
[2] E.B. Sveen, M.B. Øgaard, J.H. Selj, G. Otnes, PV system degradation rates in the Nordics, EUPVSEC proceedings, 2020.
[3] B.R. Paudyal, A.G. Imenes, Performance assessment of field deployed multi-crystalline PV modules in Nordic conditions, PVSC proceedings, 2019.
[4] M. Rinio, U. Enarsson, C. Hansen, A fast software check for PV systems, EUPVSEC proceedings, 2022.
[5] E. Tonita, D. Jordan, S. Ovaitt, H. Toal, K. Hinzer, C. Pike, C. Deline, Long-term photovoltaic system performance in cold, snowy climates, Progress in Photovoltaics: Research and Applications, 2025.
[6] J. Zuboy et al., Getting ahead of the curve: Assessment of new photovoltaic module reliability risks associated with projected technological changes, IEEE Journal of Photovoltaics, 2024.
Last update: 27.4.2026