"I'm an early adopter of new technology," says Gavin Tait, a 69-year-old from Glasgow, with a hint of pride.
So when he received a lump sum on retirement a decade or so ago, he invested in renewable energy: solar panels on the roof, a home battery and a heat pump. "It seemed like a no-brainer," he recalls. "I could save money and help the environment - why wouldn't I?"
At first, it worked. His well-insulated home stayed warm and his energy bills fell. But over the past couple of winters, things began to change. "I noticed my electricity bills were going through the roof," he says.
This winter, he and his wife switched it off and went back to their gas boiler, which they had kept as a backup.
Gavin - who wrote in to BBC Your Voice about his experiences - says he knows what the problem was. At best gas delivers nearly one unit of heat for each unit of energy put in; his heat pump can deliver up to three or four units of heat for every unit of power. But as heat pumps run on electricity, he is now paying around 27p per kilowatt-hour, compared with less than 6p for gas that powers a boiler - more than four times as much.
