Advanced energy tech will cost more at the build stage but reduce bills in use – or will it? The Building for 2050 project, in which four developments have been built and lived in over the last five years, examines the drivers, attitudes, barriers and challenges relating to low cost, low carbon housing. How to build more such houses, which will notionally reduce energy bills for residents? But there is a payoff between the higher initial cost of clean energy technologies and the supposed reduction in bills. Will this equation work? And where does embodied energy come in?