The heat battery manufacturer has signed a memorandum of understanding with Leicester-based Fischer Future Heat to supply its Aquafficient heat batteries.
It marks the first large-scale original equipment manufacturer agreement for the Scottish firm and sets out the basis of an ongoing partnership with shared product development goals.
Fischer, which specialises in smart electric heating systems manufactured in Germany, is already replacing traditional hot water cylinders with compact heat batteries supplied by Sunamp.
Fischer said it expects to "rapidly ramp up" its activities to deliver "thousands of units per annum".
This follows a high-level appointment at Tranent-based Sunamp, which named Martin Bloom as its new chairman in April, and comes hot on the heels of a funding boost of just over £3 million as it looks to scale up.
Andrew Bissell, chief executive at Sunamp, said: “This agreement sets out the terms for our first major contract in the UK at this scale, and is a significant milestone in our long-term business plan to explore strategic opportunities nationally and internationally, and to develop meaningful collaborations."
He said that the two companies have "a shared ambition to bring new choices for consumers who care about home comfort, efficiency and the environment", adding that Sunamp heat batteries "can store four times more heat than the hot water tanks they replace, as well as cutting carbon emissions and fuel costs".
Fischer Future Heat founder and chief executive Keith Bastian said: “Our agreement with Sunamp paves the way for less reliance on fossil fuels and an increase in cleaner air and energy efficiency. The future is electric.”