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Outside a 100-year-old house on the edge of the Peak District in northern England, a heat pump’s fan blades are swiftly spinning. They’re drawing outdoor air over coils of refrigerant, harvesting warmth from that air. All air-source heat pumps do this—and they can glean heat even on cold days. But this heat pump is special. It is one of the most efficient installations of its kind in the country.

“I’m number two on there,” fizzes owner Rob Ritchie, a retired chemistry teacher, referring to the system’s position on HeatPumpMonitor.org, a kind of online leaderboard for heat pumps around the UK and beyond. “I should say it isn’t important—but it is. It’s nice being there.”

At the time of writing, real-time data suggests that for every kilowatt-hour of electricity Ritchie’s heat pump consumes, it delivers 5.5 kilowatt-hours of heat—a coefficient of performance, or COP, of 5.5. Achieving a COP of 5 or above is “absolutely incredible,” says Emma-Louise Bennett, active transition support lead at Viessmann, the company that made Ritchie’s heat pump. In the UK, average heat pump COPs tend to be between 2 and 3.

Enlarge / Fungus samples are seen on display inside the Fungarium at the Royal Botanic Gardens in Kew, west London in 2023. The Fungarium was founded in 1879 and holds an estimated 380,000 specimens from the UK. (credit: Henry Nicholls/AFP via Getty Images)

It’s hard to miss the headliners at Kew Gardens. The botanical collection in London is home to towering redwoods and giant Amazonian water lilies capable of holding up a small child. Each spring, its huge greenhouses pop with the Technicolor displays of multiple orchid species.

But for the really good stuff at Kew, you have to look below the ground. Tucked underneath a laboratory at the garden’s eastern edge is the fungarium: the largest collection of fungi anywhere in the world. Nestled inside a series of green cardboard boxes are some 1.3 million specimens of fruiting bodies—the parts of the fungi that appear above ground and release spores.