If a
space heater
is a w
ire which heats up, then it is not
100% efficient at producing heat. They also produce
visible
light, as you can easily see by
looking at one. Even
if all types of
energy produced by a
heater will
eventually be converted to
heat, if the energy like
light energy converts to heat 1000
km
away, then
it's not going to warm you up. This can
happen because of a
new-fangled architectural
invention called the window,
which can allow
light to
escape.
Nothing is 100% efficient.