Various estimates have stated that if solar heating and cooling of buildings is proved to be practical, 10% of new buildings may be solar heated within ten years. It is expected that ultimately up to 80% of thermal energy, used for heating/cooling buildings, may be obtained from the sun. At the average yearly rate of two million housing units, 20,000 new housing units represent only one percent of the yearly construction total. A total of 10% could be regarded as a crucial goal to be attained within five years at the most.

Thermal energy storage is an unavoidable necessity to spread daytime excess solar heat for use at night and possibly for another cloudy day and night. It is convenient to assume that the storage of one million Btu would be a "yardstick" to consider for winter heating applications.