The development of a Thermo-Electric Generator (TEG) for a sports saloon with a 2.0 l turbo charged gasoline direct injection (GDI) engine is described. The TEG is to be fitted in the exhaust path and is designed to reduce overall vehicle CO₂ emissions both within the New European Driving Cycle (NEDC) and the overall performance envelope of the vehicle. The stages in the design process are outlined, these include; selecting an optimal operating point within the NEDC, a detailed survey of the available volume for the TEG installation in the exhaust path and comparisons of estimates for the pressure drop and overall heat transfer for two different types of fin within a cylindrical coaxial TEG at the design point. These estimates are obtained from previously published empirical relationships and are compared with the results of numerical simulations for one fin arrangement with three different thicknesses of thermoelectric material. The results indicate that for a given fin spacing, offset fins produce a higher rate of heat transfer than plain fins but with a higher pressure drop, as reported elsewhere. For the cases studied, the agreement between the numerical simulations and the previously published methods of calculation is good, better than 85% agreement for both pressure losses and overall heat transfer. This is in part due to the uniformity of the velocity distribution on the inlet side of the fins in the simulation. One of the features of the coaxial TEG is this lack of skewness in the velocity distribution to the annular heat exchanger. To generate 300 W of electricity with current conversion efficiencies requires the extraction of at least 6 kW of thermal energy from the exhaust gas. The results indicate that this can be achieved with this initial TEG concept using a thermoelectric material thickness of 2 mm with either fin type but with the plain fins requiring closer spacing, which will entail a corresponding weight penalty. With closer spacing, the offset fins exceed design limits on the pressure drop; however, across the TEG as a whole, simulations indicate that there is pressure recovery. Hence, this drop may be acceptable.