Methodology — Gera Cold Home Risk Index

The formula

-- Step 1: depth-of-gap weight per region
depth_weight = region_avg_gap_per_FP_household / national_avg_gap
national_avg_gap = £407/yr  (England 2024, DESNZ Table 1)

-- Step 2: raw risk score per local authority
raw = pct_households_in_fuel_poverty × depth_weight

-- Step 3: normalise to 0–100 across all 296 LAs
GCHRI = round( (raw − min_raw) / (max_raw − min_raw) × 100 )

-- Example: Isles of Scilly (highest GCHRI)
raw = 17.3267 × 1.3794 = 23.9004
GCHRI = 100  (top of the normalised range)

GCHRI = 100 is the highest cold-home risk area; 0 is the lowest. The normalisation means the index is relative across the included set of English LAs — it does not imply a fuel-poverty rate of 0% at GCHRI 0.

Data sources

Both datasets are Open Government Licence v3.0. No registration or API key is required to download them.

What we deliberately do not do

• We do not impute depth-of-gap at LA level from LSOA data. DESNZ publishes aggregate gap at regional level only (not per-LA or per-LSOA). We use the published regional figure — stated openly.
• We do not extrapolate to Wales, Scotland, or Northern Ireland. DESNZ sub-regional statistics cover England only.
• We do not invent a GCHRI for areas not in the DESNZ Table 2 dataset. Crown dependencies and other non-LA geographies are omitted.
• We do not assert that GCHRI = 0 means 0% fuel poverty. City of London has the lowest rate in the dataset (6.3%) and still has a meaningful fuel poverty rate — GCHRI is relative.

Coverage

296 English local authority districts, unitary authorities, metropolitan districts, and London boroughs — all LA-level rows in the DESNZ 2024 sub-regional dataset (Table 2). England only; 2024 data period; LILEE metric. National fuel poverty rate: 9.9%. National average fuel poverty gap: £407/yr.

Frequently asked questions

What does the Gera Cold Home Risk Index (GCHRI) measure?

The GCHRI is a 0–100 index where 100 = highest cold-home risk and 0 = lowest, across 296 English local authorities. It combines the official DESNZ proportion of households in fuel poverty with a regional depth-of-gap weight that reflects how severe fuel poverty is in that region — not just how common it is.

What is the depth-of-gap weighting?

The depth-of-gap weight for each region is: region average fuel poverty gap (£/yr per fuel-poor household) ÷ national average gap (£407/yr, England 2024). Regions where fuel-poor households face a larger average financial shortfall get a weight above 1.0. This is why the South West, despite having a lower raw % than the West Midlands, can have a higher GCHRI — its fuel-poor households face a larger typical gap (older housing stock, off-gas heating, rural location).

Are any numbers estimated or invented?

No. Every underlying number is a real published figure read verbatim from DESNZ datasets (OGL v3.0). The fuel poverty proportions are from DESNZ Table 2 (LA level). The regional gap figures are from DESNZ Detailed Tables Table 6. The only computation Gera performs is the depth-weight calculation and the 0–100 normalisation — both are reproducible from the published source data.

What is the LILEE metric?

The Low Income Low Energy Efficiency (LILEE) metric is the official English fuel poverty measure since 2021. A household is fuel-poor if its dwelling is rated Band D or below on energy efficiency AND, after meeting its modelled fuel costs to a minimum standard, its residual income falls below the poverty line. LILEE replaced the older 10% metric (spending ≥10% of income on fuel) because it better targets households where energy-efficiency improvements would have most impact.

How often is the GCHRI updated?

Annually, in step with the DESNZ sub-regional fuel poverty release (typically April–May each year, covering data from the prior calendar year). The current figures are for 2024, published 14 May 2026. Each page is version-stamped with its as-of date.