This depends on specific circumstances, such as the amount of the original gas consumption and the type of heating system. With a simple replacement of the condensing boiler with a high-temperature heating system, approximately 30% less gas is required compared to the existing condensing boiler. The emission of CO2 is also 30% lower. With heating systems with lower output temperatures (such as underfloor heating), the savings can be up to 40%. Savings of up to 50% can be achieved by replacing older (VR) heating appliances or combining complementary sustainable techniques in the heating system. By insulating the house, much higher combined savings can be achieved, depending, of course, entirely on the degree of insulation.