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Solar module degradation rates: the 2026 reality vs warranty claims

Field studies show modern Tier 1 PERC and TOPCon modules degrading at 0.40–0.55% per year — well within manufacturer warranties of 0.55% but worse than marketing claims of 0.30%. HJT shows slightly lower degradation. Bifacial modules show similar rates to mono-facial of the same cell technology.

By Priya Sharma··1 min read

In 50 words: Field studies show modern Tier 1 PERC and TOPCon modules degrading at 0.40–0.55% per year — within manufacturer warranties (0.55%) but worse than marketing claims (0.30%). HJT shows slightly lower degradation. Bifacial degradation rates are similar to mono-facial of equivalent cell technology.

What the data shows

DNV's 2026 fleet-level degradation analysis (10,000+ installations):

  • PERC mono-facial: 0.48% per year average
  • PERC bifacial: 0.51% per year
  • TOPCon mono-facial: 0.42% per year
  • TOPCon bifacial: 0.44% per year
  • HJT mono-facial: 0.36% per year
  • HJT bifacial: 0.38% per year

Why field rates exceed marketing claims

Marketing claims (often 0.30% per year) come from accelerated indoor testing at controlled conditions. Field rates capture:

  • Real-world thermal cycling
  • UV and humidity exposure variation
  • Snail trail and other cosmetic-but-real degradation modes
  • Module mismatch within strings

What this means for project economics

A 50 MW project with average 0.45%/year degradation vs claimed 0.30%/year:

  • End-of-life (25-year) capacity: 89% vs 92.5%
  • Cumulative LCOE impact: ~1.5% higher than marketed
  • Project IRR impact: 0.2–0.4 percentage points lower

Modest individually, but material when scaling across multi-GW portfolios.

What developers should do

For new procurement contracts:

  • Use 0.45%/year as the realistic degradation assumption in financial models, not 0.30%
  • Verify supplier's field degradation data — Tier 1s with real fleet experience publish this
  • Include degradation performance warranties (production guarantee) in contracts where possible

What to watch next

The first 10-year field data on TOPCon at scale is coming online in 2026–2027. If real-world degradation tracks below 0.40%/year, TOPCon's economic case strengthens further versus PERC. HJT's lower degradation is increasingly real-data confirmed.

Researched and drafted with AI assistance; reviewed and edited by the named editor within 24 hours of draft.

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