Across most of the U.S., residential geothermal heating systems
depend on electric heat pumps to boost low-grade heat collected
from soil or groundwater to temperatures high enough to be
useful. But the lucky inhabitants of a few geologically
privileged areas can heat their homes by tapping directly into
naturally occurring hot groundwater.
One such place is Klamath Falls, Ore. Most of the city's
downtown core - including its sidewalks - has been heated by an
elaborate municipal geothermal plant since the early 1990s.
Area homes and ranches, however, have relied on simpler systems
at least since the 1930s....