Among the firms offering R290-based heat pumps are Octopus Energy, a renewable energy company. It recently announced a heat pump called Cosy 6, which can heat water up to a maximum of 80C. In principle, homeowners could change their heating system over with little fuss, says Alex Schoch, head of flexibility. “Combi boiler out, heat pump in,” as he puts it. This could make heat pumps viable in a broader range of UK homes, which are notoriously poorly insulated in comparison with much of Europe.