Radiator Labs becomes Kelvin, takes $30M to push radiator retrofits into heat pumps

A climate-tech company making smart radiator covers that give tenants app control over steam heat, sold to buildings on subscription.

$30M Series A led by climate-tech investor 2150, with the Schmidt Family Foundation, Partnership Fund for NYC and several previous investors; valuation undisclosed.

Radiator Labs was born to solve steam radiator night sweats, a common problem in cities like New York. Founder Marshall Cox's Cozy debuted on Kickstarter as a cloth cover for renters — think giant oven mitts — and evolved into sleeker metal covers offered to whole buildings on subscription.

In May 2023 the company rebranded as Kelvin — 'a name that was concise and descriptive of our mission' of upgrading temperature control for occupied spaces as cheaply as possible — and closed a $30M Series A led by 2150. It said the money would fund expansion into the UK, Germany and other parts of Europe, and that it planned to start offering heat pumps, heating tech crucial to building decarbonization, later that year.

The radiator cover gave Kelvin a paid foothold in exactly the older, steam-heated buildings where heat-pump conversion is hardest.

Subscription pricing per apartment proved tenants and landlords would pay for comfort retrofits, de-risking the wider platform bet.

Climate-focused capital (2150, Schmidt Family Foundation) matched the expansion thesis: decarbonization economics, not gadget novelty.

A wedge product can earn the right to a platform: fix one unbearable problem first, then rebrand around the system the fix made possible.

As of May 18, 2023, Kelvin was a newly renamed, $30M-funded company planning European expansion and a heat-pump offer before the end of the year, with Cozy subscriptions running at $10–15 per apartment per month.