The heightened interest in building energy performance has exposed problems with reporting and benchmarking.  Established conventions may no longer suit current needs, and new complications are emerging as national and corporate reporting (e.g. for carbon accounting and trading) begin to impact on the certification and labelling of building energy performance. If we are to achieve genuinely low-energy and carbon buildings, we need to get much better at reporting and benchmarking our intentions and outcomes, and particularly making performance visible and communicating it to all the people concerned.  In design, this could help us to reduce the persistent differences between regulatory expectations, design estimates, modelling results, and actual performance in-use.  In use, it needs to focus building owners and operators on purposeful improvement. Bill will consider how communication of energy performance might be improved, reporting errors reduced, and benchmarking become more oriented towards practical action.  He will draw on his experience in Britain and Europe (most recently with Display Energy Certificates, Landlord's Energy Statements, and CIBSE benchmarks), and his recent work at LBL for the California Energy Commission.