The micro-scale wind turbine industry is expanding in the UK with institutional support and UK legislation encouraging the development of numerous companies with a profusion of design options. The application of micro wind turbines in urban environment is encouraged in the UK via a grant scheme which provides a proportion of the initial capital costs. This development is predicated on the assumption that micro wind turbines have the potential to reduce built environment CO2 emissions. Current methods of estimating the wind speed are reported to over predict by approximately 2.0 m/s. The energy yields of a range of typical micro wind turbines (in the 0.4-2.5 kW size range) were estimated here using two wind speed datasets sited within I km of each other recorded with a temporal precision of 10 min. The annual energy yield of a 1.5 kW turbine was found to be 277 kWh and 2541 kWh for the two sites analysed indicating the problem with the current method of yield estimation. Between 33 and 55% of the electricity generated would be exported dependant on the dwelling's electrical demand. For the high yield site, the simple economic payback of this turbine was found to be 26.8 years i.e. beyond the likely life time of the turbine with CO2 savings of 1093 kg CO2 The research suggests that this technology does represent a possible route for reducing CO2 emissions but this is unlikely to be realised unless an adequate method is found for more accurately predicting energy yield at a specific site. (C) 2007 Elsevier B.V. All rights reserved.