Stealing heat, or not? Say I hook a 1KW steam engine to the steam heat in my apartment, and generate 1KW of electricity (the engine is 1KW mechanical, not 1KW thermal) from it, so I don't have to pay ConEd. 
That means I am getting 1KW less heating power for the same amount of steam. Does it take the landlord's heating plant 1KW more to keep my room at the same temperature?
 A: Before you hook up your generator you're using electricity from the mains. If, as you say, the electricity is used only in your room then it ends up as heat and heats your room. For example the electricity used by your PC is expelled by the cooling fan as hot air and heats your room that way.
Because your room has been heated by the electricity you use, the temperature difference between the steam radiator and your room is lower, which means heating your room requires less heat from the steam and therefore your landlord needs to spend less on fuel.
If you don't use any electricity from the mains all the heat has to come from the steam. Some of the heat comes directly from cooling the steam, and some comes from generating electricity and (eventually) turning that into heat, but in the end it all comes from the steam. That means the landlord needs to burn more fuel to keep the steam at the right temperature, so you are taking the energy from the landlord.
A: The answer is yes, you are stealing energy. You are removing steam from the circuit of heating by your engine. 
The heating plant  is supplying this energy to you and it will replace it by heating more cool water to bring the steam pressure to the necessary level to keep all radiators at the desired temperature, including your radiators.The parameters of the steam are designed with a specific temperature and pressure to cover the geometry of the radiators and the building.
Maybe it will be easier to understand the "stealing" if you think of doing something similar to hot water radiators, i.e. take your hot bath from the hot water in the radiator. (it has been done).
