Steam boilers are a less effective way to heat a house then hot-water boilers, according to Energy.gov. Steam boilers can be used to distribute heat evenly to a home in several ways but cannot be set on a time delay the way a hot-water boiler can.
The best way to rate a steam-fired boiler is in its annual fuel utilization efficiency or AFUE, states Energy.gov. This number does not take into account heat loss to ducting and the circulation system. About 10 percent of fuel is wasted as exhaust and escapes out the flue of the boiler unless it is electric. Using a condensation boiler that takes water left over from the ignition process and uses it to continue the heating process can further improve the efficiency of a steam boiler
If used for additional applications, such as radiant heat flooring, the benefits can make up for lack of efficiency. Steam boilers operate at a higher temperature, so more energy is lost to the process of maintaining heat, as compared to lower-heat systems. When replacing an old system or retrofitting it, several innovations in technology can be applied to make the unit consume less fuel and produce more heat. Derating gas burners is one simple way to lower the fuel consumption while maintaining the heat provided by the system.