The latest round was led by Brookfield, one of the largest global investors in infrastructure. Brookfield has also invested in residential infrastructure specialists Thermondo in Germany and Enercare in Canada and the US.
Founders Mel Butler, Andy Kerr and Keith Jones launched BOXT in 2017, after developing a digital platform.
A spokesman said: “Growing to over 70 employees since its inception in 2017, BOXT aims to double its workforce in the next 18 months. The digital heating disruptor has amassed a network of over 3,000 engineers, with a view to increasing this to 6,000 by 2023 to meet customer demand.”
BOXT founder and CEO, Andy Kerr, said: “The company has continually delivered double-digit growth since 2017.”
Mr Kerr added: “Bucking the trend of the traditional UK heating industry, we’ve achieved over 50 per cent underlying sales growth despite the challenging economic circumstances throughout the Covid-19 pandemic."