ESOS makes large UK undertakings audit their energy use every four years. Since Phase 3, it grew teeth: a public action plan with annual progress updates. Phase 4 compliance is due by 5 December 2027 — and the assessor's report will list your bare valves whether you read it or not.
UK undertakings with ≥250 employees, or turnover > £44M together with a balance sheet > £38M — assessed at the qualification date (31 Dec 2026 for Phase 4). Corporate groups qualify together if any UK member qualifies.
| New requirement | Status |
|---|---|
| Energy intensity ratios | mandatory in the report |
| Action plan | public, filed after the audit, with the measures you intend to take |
| Annual progress updates | you report against your own plan every year |
| Net-zero element | consultation to align audits with net-zero pathways |
Source: Environment Agency ESOS guidance; Energy Act 2023 enabling powers.
Boilers, kilns, heat exchangers, valves and steam lines lose energy continuously. Inzonex makes patented (UK GB2508992.1) removable modular insulation — snap-fastened covers engineered per temperature tier, not generic off-the-shelf jackets:
ESOS lead assessors work from site walk-rounds and bills. The classic first-page findings in any steam- or hot-water-using plant: bare valves, flanges and fittings (each DN150 valve at 180 °C ≈ 13 MWh/yr, ASTM C680), failed steam traps, and uninsulated condensate return. They appear first because the payback is shortest — typically under 2 years — and the evidence is a thermal image.
Once it's in the report, it's in your action plan, and you update progress on it annually. The cheapest way to make that update positive: fix the heat losses and book the saving — format it here.
