Todays marketable light water reactor (LWR) nuclear power plants allow an appropriate design to extract heat for the purpose of district heating. Besides the desired reduction of thermal emission, the electrical output will also decrease. With helium-cooled lugh-temperature reactors or modified LWRs, nuclear generation of low-temperature heat can possibly be made more economical The presence of widespread district heat networks would allow distribution of more than 1000 MJ/s from these power plants. The desired saving of primary energy, however, can be attained only by high investments.