Underlying trends of heating and cooling degree-days (HDDs and CDDs) in major climate zones across China in the 20th and 21st centuries were investigated using measured data and predictions from general circulation models for the low and medium emissions scenarios. There are five major climate types, namely severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter. Because of the varying topology and elevations, the severe cold and cold climates cover three different regions. Within China there are, therefore, nine climate zones altogether. All the nine climate zones displayed distinct decreasing and increasing trends in the HDDs and CDDs, respectively. A reduction in HDDs would result in less winter heating and an increase in CDDs would lead to more cooling requirement. In the severe cold climate zones reduction in heating requirement tend to outweigh the modest increase in summer cooling. In the hot summer and cold winter climate zones where both winter heating and summer cooling requirements are important, the magnitude of reduction in heating and the magnitude of increase in cooling could be comparable. In general, the impact on the total building energy use would be either positive or negative. But for non-domestic buildings with large internal heat gains (e.g. people, electric lighting and equipment) where the annual cooling load tends to be larger than the heating load, the overall impact would certainly be an increase in the total building energy use. The most significant impact on energy use in the built environment, however, would occur in the hot summer and warm winter climate zone where building energy use is dominated by cooling requirement. Space heating is provided largely by oil-or gas-fired boiler plants, whereas space cooling mainly relies on electricity. This would result in a shift towards more electrical demand and could have important implications for the nationwide energy policy. Electricity has a much higher carbon footprint than natural gas. More work is required especially on the costs of changing electricity demand and carbon emissions from different fuel mix in the energy sector to cater for the likely impact of climate change on the energy use in the built environment.