K & H makes heaters specifically designed for what you want:
http://www.khmfg.com/products/heatedDogBeds.htm

We bought the cat version (just a smaller version) and I'm impressed with
the construction and build quality. Their products are available online,
but my wife found one at a local pet store. The cat version uses the
equivalent of a 40-watt bulb, so we just plugged it in for the winter and
will unplug it in spring.


"DoDa" wrote in message
...
Looking for any ideas on the best way to heat a doghouse for the winter?

Donna