The street in Cornwall heated by the world's first underground energy network

• Watch Charlotte Gay's report.

A Cornish street has begun to be heated by energy generated below the ground and pumped to the surface, in a pioneering new trial to retrofit homes.

The multimillion pound "Heat the Street" project has drilled 42 boreholes to make a heat energy network under the Collins Parc estate in Stithians.

What makes it a world first is how the network has been plumbed into the public road and is giving the option for all of the homes on the street to be connected to the grid.

Caroline Bolitho's ground source heat pump was the first to be switched on today (23 March) and she said she's "amazed" at how quiet it is compared to her old oil burner.

"Just whirr and then it just started up, it's just so efficient. With the oil boiler it was a huge pump, and the noise and the smell, even if you're in another room, you could smell it."

She added it cost a grand to fill up her tanker and she now has high hopes this will be a cheaper and greener alternative.

Lisa Treseder, from the Cornwall-based Kensa Group behind the project, said: "We're trying to show that there's a really good alternative to the gas networks."

"This would save houses about 80 percent of the carbon they currently use with the gas central heating system, and if you use the road, you can install this kind of infrastructure anywhere in the UK so we could decarbonise any house in the whole of the UK."

The village of Stithians is not connected to mains gas, so this heat pump network hopes to replicate the grid structure for the houses in the "Heat the Street" project.

It has been highly subsidised, using £3.6m from the EU Regional Development Fund to significantly reduce the cost of putting in the heat pump network, which would have otherwise been an expensive installation for homeowners.

Lisa said at the moment only 40-50,000 heat pumps are being installed annually in the UK. For the UK Government to meet its 600,000 target, they need to support projects like this, according to those behind it.

"This is our showpiece in Cornwall. So, Stithians is our example of how we're going to make this happen across the rest of the UK. We can prove that we can do this engineering we can prove that people want it and therefore this is a business model that could really work for the UK."

How does a ground source heat pump work?

A ground source heat pump is a way to transfer heat from the ground outside your home to heat your radiators, underfloor heating, and hot water cylinder for your hot taps and showers.

The Energy Saving Trust describes the process as a mixture of water and antifreeze flowing around a loop of pipe, buried in your garden or outdoor space.

Heat from the ground is absorbed into the fluid, which then passes through a heat exchanger into the heat pump. This raises the temperature of the fluid and then transfers that heat to water.

The trust also says the typical costs of a GSHP is around £24,000 if your ground loop is buried in trenches, and could be around £49,000 if you need to dig a borehole.