A redesign of lighting systems in office or public buildings helps to save electricity and improve lighting quality, as the office building of the Austrian company Bartenbach on the photos shows. However, lighting systems are rarely upgraded: For example, in Germany, retrofits can only be found in 3 % of the existing building stock and 75 % of lighting systems are out of date, as they are older than 25 years. To support planners and investors in their decision on what would be the most apt lighting retrofit, the researchers of Task 50 of the IEA Solar Heating and Cooling Programme, Advanced Lighting Solutions for Retrofitting Buildings, have launched a website called www.lightingretrofitadviser.com and an app for Android and iOS devices. Both provide stakeholders with information about successful case studies of lighting retrofits in buildings, a database of technologies as well as tools, for example, to give direct onsite support for decision making, whether it is sensible to retrofit a lighting system. A webinar on 21 March explained all the services and features of the new website and app. A recording of it is available online.