Aquaheat's engineering and contracting business, with offices in Auckland, Wellington and Christchurch were purchased in September 2012 and has been integrated into the Horizon Energy and is pursuing a range of business and growth initiatives.
Aquaheat's commercial building services include refrigeration, heating systems, fire protection, plumbing and drainage and specialist wall and roof cladding systems.
"We are on track with our business plans and the loss of this key long-term customer will be a serious set-back for Aquaheat."
Tait said Horizon Energy is committed to building a successful business model outside of its core electricity lines distribution business which is in the eastern Bay of Plenty.
"I expect we will have a clearer picture of our financial exposure as a result of this receivership within a few days once we have reviewed our commitments and obligations under the many contracts we have with Mainzeal. We will advise shareholders and the market as soon as we have more certainty," said Mr Tait.
Horizon's after tax profit was $6.4 million for the year ended 31 March 2012.