Knowledge in the form of data is important for not only increasing the energy efficiency of buildings but also for having buildings support the future Danish energy system. However, data needs to be as accessible in a digital form for easy use. The Danish Building and Housing Register (BBR) was established in 1977. BBR is a digital and online database containing information of all Danish buildings. Together with the digital EPCs, BBR gives the Danish government an overview of the Danish buildings stock, which make it possible to design e.g. subsidy schemes for energy renovation.

Much has happened since 1977. Today all Danish buildings have smart electricity billing meters and a roll-out of smart heat meters for district heating customers is well under way. Readings from smart meters contain information on the hourly energy demand. This knowledge is very important in the transition of the energy system away from fossil fuels to renewable energy sources such as wind and solar. Energy production from wind and solar is, however, very fluctuating. The energy production will thus in the future often not be in phase with the demand. There is, therefore, a need for the demand to become flexible for preventing both shortage and curtailment of energy. Denmark is aiming at an electrification of the energy system using large heat pumps in district heating systems and individual heat pumps in more rural areas. Buildings can help to stabilise the power grid as they can store heat from periods with much energy to periods with shortage. Danish buildings have large thermal mass in their constructions to store heat. However, it is important that only little heat is lost. So, energy efficient buildings play a key role for the stability of the future energy system. Buildings will especially become valuable as they can solve problems in the distribution grid, – e.g. reduce congestion problems when many charge EVs, but also increase energy use, when individual PV system produces excess electricity.

For this, online data from e.g. smart meters is a prerequisite, so that the energy utilities know how their customers react in different situations. The utilities may send out e.g. a price signal on which the control of the building reacts to. The control in the building will based on historic measured energy demands dispatch the energy use to periods with much energy in the energy system. But as each building only can deliver little energy flexibility, there is a need for an entity, which can collect the flexibility from buildings and bit this into the flexibility market. This entity is an aggregator. Denmark have started to establish the legislation for both making data from smart meters “free” (with respect for data protection and privacy) and for having a smooth phase in of aggregators making energy flexibility from e.g. buildings a valuable asset for the future Danish energy system. The control for enabling energy flexibility may also be utilised for making buildings more energy efficient.