Unlocking Energy Efficiency with ESOS Phase 4

Phase 4 Is No Longer “Expected” — the Rules Are Published

The old version of this article said Phase 4 was “expected” to introduce tougher requirements and mandatory net-zero assessments. The Environment Agency published dedicated Phase 4 guidance on 30 July 2026, reflecting the ESOS Regulations as amended in 2026.

That means businesses should now work from the final rules rather than older consultation-era predictions.

Current ESOS Phase 4 Timeline

Who Qualifies?

Subject to the detailed ESOS rules and group provisions, an organisation can qualify as a large undertaking if it meets either of these tests:

• 250 or more employees; or
• Annual turnover above £44 million and annual balance-sheet total above £38 million.

Group structure and accounting history can affect whether an undertaking is in scope, so businesses near the thresholds should confirm their position using the official guidance or their ESOS compliance adviser.

What Actually Changed for Phase 4?

Where Compressed Air Fits In

Compressed air can be one of the larger electrical loads on a manufacturing site, particularly where compressors run for long hours, pressure is set too high, leaks are widespread or control is poor.

A compressed-air assessment can therefore provide useful evidence and recommendations within a wider ESOS energy assessment.

What a Measured Compressed-Air Audit Can Reveal

Use Logged Data, Not Headline Savings Percentages

The current Tanair energy-saving audit service uses a minimum 14-day logging period to capture real operating conditions and demand variation. That is much stronger than estimating savings from compressor motor size alone.

VSD Can Be an ESOS Opportunity — Not an Automatic Answer

The old article strongly positioned variable-speed compressors as the central Phase 4 solution. VSD can reduce wasted energy where site demand genuinely varies, but it should be justified by the load profile.

Current Tanair VSD Range

The live article contains a large product feed. The most useful Tanair VSD routes are retained here without embedding prices that may become stale.

From Audit Recommendation to Action Plan Evidence

Phase 4 places greater emphasis on reporting achieved savings and reviewing action-plan commitments. That makes measured project evidence more useful.

How Compressed Air Systems UK Can Help

Compressed Air Systems UK can support the compressed-air part of an energy-efficiency programme with measured audits, system analysis, leak detection, equipment selection and implementation support.