Mite said that the purchase would support its ambition to be a leading provider of green energy solutions.
Mite will pay an initial of £8m, with deferred payments of up to £4.4m by 2025, linked to performance targets. The transaction is expected to complete on 30th June.
For the year to 31st March 2022, employee-owned Custom Solar generated revenues of £15m and pre-tax profit of £2m. It has gross assets valued at £7m.
The staff and senior management of Chesterfield-based Custom Solar, including managing director Matthew Brailsford, will join Mitie with the business.
Simon Venn, Mite managing director, technical services, said: “The acquisition of Custom Solar continues Mitie’s strategy of investing in high growth, high return businesses within the energy and decarbonisation market to help our customers accelerate their path to net zero.
“Custom Solar’s expertise in large scale commercial solar deployments, combined with Mitie’s high voltage connection and project management expertise, will enable us to offer end-to-end renewable power generation at scale. With our client base including national brands, public sector organisations and critical infrastructure providers, this is yet another element of our support to help decarbonise Britain.”