"Steam systems are generally less efficient than hot water heating systems, but the efficiency gain of upgrading to hot water is probably not worth the expense"
I have heard this asserted just about everywhere universally, without a single justification. Why is steam heat less efficient? Is it intrinsically less efficient than hot water-based heating systems, or is it simply because its typical installation is more wasteful? My guess is that steam is less efficient because all the old steam pipes have had their asbestos insulation removed and haven't been reinsulated since. Add to that the fact that steam is much hotter and has less heat capacity than water and you have a recipe for a very inefficient system.
But bad practice doesn't mean steam heat is less efficient.
And what about other types of home heating systems, like forced hot air? How efficient are they? Does the energy source matter as far as efficiency goes? Are oil-burning boilers/furnaces more efficient than gas burning ones?
josh