{
  "slug": "solar-heat-penalty",
  "title": "The Heat Penalty: What Warming Does, and Does Not Do, to Solar Yield",
  "url": "https://solaranalytica.com/solar-heat-penalty",
  "summary": "Panels are rated at 25°C but run at a modelled 53°C in the average market, giving up 9.8% of nameplate to heat before climate change is counted. Twenty years of NASA record put the additional 25-year warming penalty at a third of a percent on average: the heat tax is large, the drift is a decimal, and the module choice is worth several times more.",
  "license": "Free to use with attribution to Solar Analytica (solaranalytica.com). Underlying figures are named to their public sources below.",
  "csv": "https://solaranalytica.com/reports/solar-heat-penalty/data.csv",
  "datePublished": "2026-04-16",
  "lastReviewed": "2026-04-16",
  "sources": [
    {
      "title": "NASA GISTEMP v4: GLB.Ts+dSST global annual means (1951-1980 baseline)",
      "url": "https://data.giss.nasa.gov/gistemp/"
    },
    {
      "title": "NASA MERRA-2 reanalysis (market temperature series, 1994-2024)",
      "url": "https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/"
    },
    {
      "title": "NASA CERES EBAF (surface and plane-of-array irradiance)",
      "url": "https://ceres.larc.nasa.gov/"
    },
    {
      "title": "Solar Analytica methodology (yield model and data standards)",
      "url": "https://solaranalytica.com/methodology"
    }
  ],
  "figures": [
    {
      "id": "static-heat-tax",
      "title": "The static heat tax. PERC vs HJT annual loss, sorted, plus the set average",
      "unit": "%",
      "valueLabel": "PERC heat loss",
      "valueBLabel": "HJT heat loss",
      "caption": "Annual output lost to cell temperature: PERC (grey) against HJT (blue), per market. Solar Analytica yield model on NASA MERRA-2 and CERES; full figures in the table below.",
      "series": [
        {
          "label": "Bamako, Mali",
          "value": 14.3,
          "valueB": 9.8
        },
        {
          "label": "Jodhpur, India",
          "value": 14.3,
          "valueB": 9.8
        },
        {
          "label": "São Paulo",
          "value": 11.1,
          "valueB": 7.6
        },
        {
          "label": "Seville",
          "value": 11.1,
          "valueB": 7.6
        },
        {
          "label": "Perth",
          "value": 9.9,
          "valueB": 6.8
        },
        {
          "label": "Berlin",
          "value": 7.1,
          "valueB": 4.9
        },
        {
          "label": "Helsinki",
          "value": 5,
          "valueB": 3.4
        },
        {
          "label": "Reykjavik",
          "value": 4.4,
          "valueB": 3
        },
        {
          "label": "40-market average",
          "value": 9.8,
          "valueB": 6.7,
          "average": true
        }
      ]
    },
    {
      "id": "gistemp-anomaly",
      "title": "The record. NASA GISTEMP anomalies, the 2024 record as the one signal reading",
      "unit": "°C",
      "caption": "Global surface anomaly against the 1951-1980 baseline, 2004 to 2025. One reading is the record: 2024. NASA GISTEMP v4, verified against the published NASA table.",
      "series": [
        {
          "label": "2004",
          "value": 0.53
        },
        {
          "label": "2005",
          "value": 0.68
        },
        {
          "label": "2006",
          "value": 0.64
        },
        {
          "label": "2007",
          "value": 0.67
        },
        {
          "label": "2008",
          "value": 0.54
        },
        {
          "label": "2009",
          "value": 0.66
        },
        {
          "label": "2010",
          "value": 0.73
        },
        {
          "label": "2011",
          "value": 0.61
        },
        {
          "label": "2012",
          "value": 0.65
        },
        {
          "label": "2013",
          "value": 0.68
        },
        {
          "label": "2014",
          "value": 0.75
        },
        {
          "label": "2015",
          "value": 0.9
        },
        {
          "label": "2016",
          "value": 1.01
        },
        {
          "label": "2017",
          "value": 0.92
        },
        {
          "label": "2018",
          "value": 0.85
        },
        {
          "label": "2019",
          "value": 0.98
        },
        {
          "label": "2020",
          "value": 1.01
        },
        {
          "label": "2021",
          "value": 0.85
        },
        {
          "label": "2022",
          "value": 0.9
        },
        {
          "label": "2023",
          "value": 1.17
        },
        {
          "label": "2024",
          "value": 1.28
        },
        {
          "label": "2025",
          "value": 1.19
        }
      ]
    },
    {
      "id": "warming-drift",
      "title": "The warming drift, market by market. Berlin is the extreme; four run negative",
      "unit": "%",
      "caption": "Added loss by year 25 at each market's own 1994-2024 MERRA-2 trend, PERC modules. Negative bars reflect a negative local trend in the window, not a cooling forecast.",
      "series": [
        {
          "label": "Berlin",
          "value": 0.83
        },
        {
          "label": "Seoul",
          "value": 0.7
        },
        {
          "label": "São Paulo",
          "value": 0.67
        },
        {
          "label": "Albuquerque",
          "value": 0.65
        },
        {
          "label": "Madrid",
          "value": 0.63
        },
        {
          "label": "Perth",
          "value": 0.33
        },
        {
          "label": "Jodhpur",
          "value": -0.15
        },
        {
          "label": "Cape Town",
          "value": -0.33
        }
      ]
    },
    {
      "id": "what-each-effect-costs",
      "title": "What each effect costs. The module choice against the warming drift, in dollars",
      "unit": "US$ per kW per year",
      "valueLabel": "Warming drift at year 25",
      "valueBLabel": "Choosing HJT over PERC",
      "caption": "US dollars per kilowatt of panels per year at 2025 retail tariffs: the modelled warming penalty at year 25 beside the value of choosing an HJT module over PERC, via the price and yield join.",
      "series": [
        {
          "label": "Berlin",
          "value": 3.8,
          "valueB": 10.9
        },
        {
          "label": "Perth",
          "value": 1.2,
          "valueB": 12.8
        }
      ]
    }
  ]
}