Energy audits are not just for ESOS-mandated large enterprises — SMEs can save tens of thousands of pounds a year by identifying waste they did not know existed. This guide explains the three audit levels, what each costs, what they uncover, and how to commission one.
The three levels of business energy audit
Level 1: Walk-through audit
A 1-3 hour site visit by an auditor who reviews your bills, meter setup, lighting, heating and obvious waste sources. Cost: free to £500. Output: a short report with 5-10 quick-win recommendations and rough payback estimates.
Level 2: Targeted audit
A 1-3 day investigation including sub-metering, equipment inventory, occupancy analysis and detailed bill validation. Cost: £1,000-5,000. Output: a 30-50 page report with quantified savings, capital cost estimates, payback periods and an implementation roadmap.
Level 3: Investment-grade audit
A 1-4 week deep-dive including building performance modelling, full equipment lifecycle analysis and risk-adjusted ROI for each intervention. Cost: £5,000-25,000. Often required for capital approval or external grant applications.
What a business energy audit typically uncovers
- Lighting left on out-of-hours (15-30% of typical office lighting load).
- Heating set above the comfort range or running outside occupancy.
- Cooling and heating fighting each other (mis-set thermostats, opposing systems).
- Always-on equipment (chargers, vending, idle machinery).
- Compressed air leaks (10-30% of compressor load in many factories).
- Old motors, fans and pumps running at full speed when variable-speed drives could match demand.
- Wrong tariff for the consumption profile (e.g. single-rate where Economy 7 or HH would save).
- Missed bill errors, wrong VAT rate, missed CCL exemption.
ESOS: when audits become mandatory
The Energy Savings Opportunity Scheme (ESOS) requires UK enterprises with >250 employees, >£44m turnover, or >£38m balance sheet to undergo a Phase 4 ESOS audit by 5 December 2027. Audits must cover at least 90% of total energy use across all UK operations and be signed off by a registered Lead Assessor.
How to commission a business energy audit
- Define scope: which sites, which energy types, which level of audit.
- Tender to 3-5 audit firms (BREEAM-trained or CIBSE-LCEA accredited preferred).
- Provide 12 months of bills, meter list and floor plans upfront.
- Schedule site visits.
- Review draft report and challenge assumptions.
- Build implementation plan with priority, cost and payback for each recommendation.
Frequently Asked Questions
A walk-through audit costs £0-500, a targeted audit costs £1,000-5,000 and an investment-grade audit costs £5,000-25,000+. Free audits are often offered by suppliers or brokers as a sales aid.
UK SMEs typically save 10-25% on annual energy spend after implementing audit recommendations; large industrial users save 20-40%. Payback on audit fees is usually under 6 months.
Only for large enterprises under ESOS (>250 employees or >£44m turnover) every 4 years. Other businesses are not legally required to audit but most do voluntarily because the savings far outweigh the cost.
An EPC rates a building’s asset performance based on construction; an energy audit reviews actual operational consumption and behaviour. An EPC is a legal certificate; an audit is an advisory report with quantified savings opportunities.
Look for CIBSE-LCEA accredited assessors, BREEAM AP qualified firms, or ESOS Lead Assessor registered consultancies. Avoid auditors tied to a single supplier or technology vendor.
Want to combine a free walk-through audit with an energy procurement review? Get a free 60-second business energy quote and ask for the audit add-on.
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