Whether it's a new building or the modernisation of an old building: Anyone planning an upgrade of their heating system should take a closer look at the heating systems of the future. Because while fossil fuel heating systems are usually cheap to buy, they will cost a lot of money to operate over the next few years. Natural gas and heating oil are dependent on the world market and at the same time are only available in limited quantities. This is why heating systems based on heating oil or natural gas are not future-proof. Fossil fuels are also subject to carbon tax, which makes them even more expensive. Modern heating systems using renewable energy sources such as solar or heat pumps protect the environment. Energy from the sun, the air, the earth or the water is available for free. This greatly reduces energy costs in the future. Energy-efficient heating systems make property owners more independent of energy suppliers and politics. Heating systems such as heat pumps, solar thermal energy or heating with biomass contribute to the transition of the heating sector as a significant part of the energy transition. But which heating system of the future is the right one for old or new buildings?