The Delft University of Technology has built a solar powered mouse, testing whether renewable energy products, with higher functionality and a touch of design, can encourage users to adopt modern and consistently sustainable conduct. They even have the Minister of Housing and the Environment using one. They are testing the "willingness of the user to adapt his behaviour to favourable light conditions by regularly charging the unit with daylight from the window, and the computer usage pattern. With solar energy, under ideal circumstances charging can occur a factor of five times quicker than in the current situation. Over time it is estimated that several hundred million batteries could be saved annually on a global scale."