The plant was grown in Mr Hilliard's solar room
A 16ft (5m) banana plant with four hands of fruit has been grown in an energy-efficient house in Stroud, Gloucestershire.
When Mike Hillard, 64, bought the plants to provide shade, he was told they would not bear fruit.
"I will probably cook them like a plantain fried with rice," he said.
Mr Hilliard, an ecology campaigner said the bananas bloomed in his solar room which stays between 10C and 16C above the outside temperature all year round.
"This has all been done by the English sunshine in my solar room, which provides my house with an oxygen-rich atmosphere," he said.
"It has been called the most energy-efficient house in the world," he said.
He added: "Now they are growing into a forest, and I've got seven babies.
"Mine have grown to four or five inches and they are edible."
A spokesman for the Royal Horticultural Society said: "It's definitely pretty unusual but given the right temperature it is possible for them to flower and bear fruit.
"He is certainly blazing a trail in the sense that not many people who have had a go at growing tropical fruit have succeeded."
Mr Hillard, an environmental architect, designed his home called Tranquility as a four-bedroom 'eco-house' made of Cotswold stone, which has total annual energy costs amounting to less than £150 a year.
In October Graham and Daphne Bath, from Hampshire, revealed that a banana tree they had been growing in their garden for the past nine years had borne fruit for the first time.