Gera Trade Cost Index (GTCI) — Methodology
Published 20 June 2026 · Data: ONS Consumer Price Inflation (published 17 June 2026)
What is the GTCI?
The Gera Trade Cost Index (GTCI) is a proprietary, reproducible cost-benchmarking metric that answers the question: "What should a household in [location] expect to pay for a [trade] in 2026, given official UK inflation data?" It is not a measured transaction price. It is an inflation-adjusted planning estimate built entirely from two real, free, government-published UK datasets.
GTCI scores run from 0 to 100, where 100 = the CPIH-adjusted national average for that trade. Scores above 85 indicate the area is at or below the national CPIH-adjusted average; scores below 65 indicate the area is notably above the national average (i.e. more expensive).
Data sources
Source 1 — ONS CPIH 04.3: Regular Maintenance and Repair of the Dwelling
- Series code
- L537 (L537)
- Dataset
- Consumer Price Inflation (MM23)
- Publisher
- Office for National Statistics (ONS)
- Published
- 17 June 2026
- Fetched
- 2026-06-20
- Licence
- Open Government Licence v3.0
- Download
- ONS Consumer Price Inflation dataset
The ONS CPIH 04.3 series (L537) measures the price change in regular maintenance and repair of the dwelling in the United Kingdom, with a base of 100 in 2015. This is the official government inflation tracker specifically for trade and maintenance services — the appropriate index for home-service cost adjustment.
Source 2 — ONS Relative Regional Consumer Price Levels (RRCPL) 2016
- Publication
- Relative regional consumer price levels of goods and services, UK: 2016
- Publisher
- Office for National Statistics (ONS)
- Index
- All-items relative price level, UK = 100
- Licence
- Open Government Licence v3.0
The ONS RRCPL is the only official UK statistic that directly measures regional differences in the general price level. We use the conservative all-items index (rather than the wider services-only dispersion) to keep regional adjustments defensible. This is the most recent RRCPL release ONS has published; it is applied as a multiplicative regional factor.
Source 3 — National typical trade rate ranges (2025)
Published UK tradesperson rate surveys (2025/2026 editions) provide the national low-to-high band per trade used as the starting point before CPIH adjustment. These are the same sources documented in apps/gera-home-web/src/lib/trade-cost-cluster.ts. They are used only to anchor the 2015-equivalent base cost (by deflating the 2025 midpoint by the 2025 CPIH 04.3 index), from which the CPIH-adjusted forward estimate is then computed.
Formula
// Step 1: Deflate 2025 national lower bound to 2015 baseline
base_2015_low = national_low_2025 / (CPIH_04_3_2025 / 100)
// Step 2: Apply CPIH + regional adjustment
adjusted_low = base_2015_low × (CPIH_04_3_latest / 100) × (RRCPL_region / 100)
adjusted_high = adjusted_low × (national_high / national_low)
adjusted_mid = (adjusted_low + adjusted_high) / 2
// Step 3: Compute GTCI score (0–100)
nat_low_adj = base_2015_low × (CPIH_04_3_latest / 100) // RRCPL=100 (national)
nat_mid_adj = (nat_low_adj + nat_low_adj × band_ratio) / 2
delta = (adjusted_mid - nat_mid_adj) / nat_mid_adj
GTCI = clamp(round(100 × (1 - delta)), 0, 100)
- CPIH_04_3_2025
- 121.04 (2025 annual average, L537, published ONS)
- CPIH_04_3_latest
- 122.026 (2026 Jan–May average, L537, published ONS)
- RRCPL_region
- ONS 2016 all-items relative price level for the ONS region (UK = 100)
- band_ratio
- national_high / national_low (preserves the published band width)
ONS CPIH 04.3 index (L537) — annual averages
Real values from ONS Consumer Price Inflation dataset, Table 37. 2015 = 100. Source: Office for National Statistics (ONS), published 17 June 2026.
| Year | CPIH 04.3 (L537) | CPIH All Items (L522) | Months in avg |
|---|---|---|---|
| 2019 | 101.942 | 107.803 | 12 |
| 2020 | 103.300 | 108.884 | 12 |
| 2021 | 107.279 | 111.614 | 12 |
| 2022 | 115.990 | 120.458 | 12 |
| 2023 | 120.191 | 128.640 | 12 |
| 2024 | 120.849 | 132.857 | 12 |
| 2025 | 121.040 | 137.990 | 12 |
| 2026 * | 122.026 | 140.818 | 5 |
* 2026 figure is Jan–May average (5 months); all other years are full-year averages. Source: ONS Consumer Price Inflation, Table 37, CDID L537 and L522. Licence: Open Government Licence v3.0.
Per-trade base costs (2025)
National typical ranges used as starting points before CPIH adjustment. The 2015-equivalent base cost is derived by deflating the 2025 midpoint using the 2025 CPIH 04.3 index (121.04).
| Trade | 2025 range | Basis | 2015 base low cost |
|---|---|---|---|
| Plumber | £40–£80 | per hour | £33.05 |
| Electrician | £40–£90 | per hour | £33.05 |
| Cleaner | £15–£20 | per hour | £12.39 |
| Handyman | £30–£60 | per hour | £24.79 |
| Boiler Engineer | £50–£100 | per hour | £41.31 |
| Gardener | £25–£50 | per hour | £20.65 |
| Painter & Decorator | £150–£250 | per day | £123.93 |
| Carpenter | £150–£300 | per day | £123.93 |
| Locksmith | £60–£120 | per hour | £49.57 |
| Pest Controller | £80–£200 | per treatment | £66.09 |
| Drainage Specialist | £70–£150 | per job | £57.83 |
Limitations and disclaimers
- Not a measured transaction price. The GTCI is an inflation-adjusted planning estimate, not a price collected from actual GeraHome bookings. Always obtain an itemised quote before committing.
- Regional adjustment is from 2016 data. The ONS RRCPL 2016 is the most recent all-items regional price level published by ONS. Regional price differentials may have shifted since 2016.
- 2026 index is partial. The 2026 CPIH 04.3 value (122.026) is an average of January–May 2026 only (5 months). It will be updated when the full-year figure is available.
- City vs region. Cities inherit the ONS region's RRCPL index. Intra-region variation (e.g. Cambridge vs Norwich within East of England) is not captured.
- National typical ranges. The base rate ranges (e.g. £40–£80/hr for plumbers) are compiled from published UK tradesperson rate surveys; they represent the typical national spread, not GeraHome-measured prices.
Compare CPIH-adjusted trade costs by location
See how your region or city compares to the national CPIH-adjusted average across 11 home trades.
Explore the UK Trade Cost Index →Contains public sector information licensed under the Open Government Licence v3.0. Sources: ONS Consumer Price Inflation (dataset consumerpriceinflation), published 17 June 2026; ONS Relative Regional Consumer Price Levels UK: 2016. Data fetched 2026-06-20.