In the Czech Republic, the condition of buildings may be evaluated as very bad. Residential estates get old and the maintenance of houses has been neglected in the long run. The technical condition of buildings is not good, sometimes substandard, maintenance is neglected, power consumption is high and operation and maintenance costs are ever increasing. To set the priorities and time schedules of modernisation is the matter of not only the owners, designers and contractors, but also architects and urban planners. The regeneration of residential areas is to be a continual process resulting in conceptual transformation of residential areas into an agreeable, well organised, friendly and safe place to live in. The result of modernisation is the increase of utility value and space standards of houses, improvement of their aesthetic quality, and of other spaces in residential houses. The subject's aim is to make an analysis of power saving measures, to find suitable solutions and to evaluate the effect of modernisation on the load of the environment and on the return on investments.