Boiler + hot water circulation through radiators is also pretty common in US and will also use a low voltage thermostat. The only exception I can think of is o

Boiler + hot water circulation through radiators is also pretty common in US and will also use a low voltage thermostat. The only exception I can think of is older gas-powered steam boilers which may use a millivolt thermostat (which have the advantage of working when the power is out). (Or electric baseboards...but who can afford to heat that way?)