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ref: Carbon calculation to v4

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Alicia Sykes
2026-05-11 08:38:32 +01:00
parent 57d5454cd0
commit b1aea27f20
1 changed files with 8 additions and 10 deletions
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18
api/carbon.js
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@@ -7,25 +7,23 @@ const log = createLogger('carbon');
const TIMEOUT = 8000;
const MAX_BYTES = 10 * 1024 * 1024;
// Sustainable Web Design model v3 constants, matches websitecarbon.com formula
const KWH_PER_GB = 0.81;
// Sustainable Web Design model v4 constants, matches websitecarbon.com formula
const KWH_PER_GB = 0.3;
const FIRST_VISIT = 0.25;
const RETURN_VISIT = 0.75;
const RETURN_DATA_PCT = 0.02;
const GRID_INTENSITY = 442;
const GRID_INTENSITY = 494;
const RENEWABLE_INTENSITY = 50;
const LITRES_PER_GRAM = 0.5562;
// Reference median grams CO2 per visit, drawn from websitecarbon's published average.
// Used to estimate a percentile rank since we lack their measured-sites dataset
const REFERENCE_MEDIAN_GRAMS = 0.8;
// Median CO2 for an HTML-only fetch at HTTP Archive's ~30 KB median
const REFERENCE_MEDIAN_GRAMS = 0.001;
// Approximate percentile via log2 distance from the reference median.
// 1 doubling above median drops 25 points; clamp to [1, 99]
// Percentile rank via log2 distance from the median, clamped to [1, 95]
const estimateCleanerThan = (grams) => {
if (!grams || grams <= 0) return 0;
const pct = 50 - 25 * Math.log2(grams / REFERENCE_MEDIAN_GRAMS);
return Math.max(1, Math.min(99, Math.round(pct)));
const pct = 50 - 15 * Math.log2(grams / REFERENCE_MEDIAN_GRAMS);
return Math.max(1, Math.min(95, Math.round(pct)));
};
// Stream the response, cap at MAX_BYTES so huge pages can't blow memory or time