The defensible starting point is the broader plumbing, heating and air-conditioning installation category—not a purported census of AI-ready HVAC firms. ONS publishes business counts, employment and turnover by employee-size band for SIC 43.22/0, alongside a separate electrical-installation category. These classifications do not directly identify field-engineer numbers, enquiry volume, software readiness or willingness to buy automation. (ons.gov.uk)
What figures can buyers and suppliers actually use?
| Measure | Figure and reference period | Source and evidence date | Interpretation and limitation |
|---|---|---|---|
| Plumbing, heating and air-conditioning installation turnover | £24.032bn, 2024 | Verified Market Size’s reproduction of ONS Annual Business Survey data; checked by that publisher 24 September 2026; ONS dataset released 26 May 2026. (verifiedmarketsize.com) | Secondary-reported official statistic. Broad contractor-industry turnover; not independently re-extracted here. |
| Nominal turnover growth | Approximately 3.4%, 2023–2024 | Desk calculation from the same reproduction: £23.238bn to £24.032bn; calculated 27 October 2026. (verifiedmarketsize.com) | Not inflation-adjusted; not AI-spending growth. |
| Registered enterprises in the category | 47,050, 2025 | Tom Riley SEO’s reproduction of ONS/Nomis UK Business Counts; page reviewed 27 October 2026. (tom-riley.co.uk) | Secondary-reported count, not a verified 2026 total. VAT/PAYE-based enterprises, rather than a list of qualified agency buyers. |
| Enterprises with 0–4 employees | 40,340, 2025 | Same secondary reproduction, reviewed 27 October 2026. (tom-riley.co.uk) | Shows why a broad company list substantially overstates the established-employer audience. |
| Indicative pool with at least five employees | 6,710, 2025 | Desk subtraction: 47,050 − 40,340; calculated 27 October 2026 from the reported counts. (tom-riley.co.uk) | A screening denominator only. It includes larger firms and office employees, not just field engineers. |
Freshness warning: Nomis announced a new UK Business Counts release on 24 September 2026. This report did not obtain a verified 2026 SIC 43.22 employment-band extract, so the 2025 figures above must not be presented as the latest available official count. (nomisweb.co.uk)
Does this validate the earlier estimate of 5,000–15,000 target businesses?
No. That range in the supplied desk notes remains an unvalidated planning assumption. The reported employee distribution suggests that a tightly defined established-employer audience is substantially smaller than the entire contractor population. (tom-riley.co.uk)
A proper addressable-market exercise should separately identify:
- Businesses in the core installation category with sufficient office and field capacity.
- Relevant maintenance, facilities-management and engineering businesses classified elsewhere.
- Groups and branches that share one procurement decision.
- Businesses with a measurable workflow problem and delivery capacity to benefit.
- Businesses whose existing software cannot already solve that problem economically.
Desk recommendation: treat headcount as an initial filter, then qualify on transaction volume, process ownership and contribution economics. Do not treat every registered heating business as a prospect for a bespoke agency retainer.
Sources cited on this page
- ons.gov.uk ↗www.ons.gov.uk
- verifiedmarketsize.com ↗www.verifiedmarketsize.com
- tom-riley.co.uk ↗tom-riley.co.uk
- nomisweb.co.uk ↗www.nomisweb.co.uk