In practice, for effective exhaust waste heat recovery, a heat exchanger must exhibit a high heat transfer performance and a reasonable pressure drop to achieve a high net power output. Therefore, a complete numerical thermoelectric generator (TEG) model used for engine exhaust gas heat recovery is presented in this paper, based on a common plate-type exhaust heat exchanger. The model not only considered the temperature gradient along the fluid flow direction, but also included the fluid heat transfer and the flow resistance characteristics. The interaction relationships between the exchanger scales, heat transfer and flow resistance characteristics, and thermoelectric performance were mainly studied in this study by numerical simulations using the Fortran program. Results show that the high TEG power can be achieved at the small cross section area, and corresponding to a small optimal module area. A small height is required when the cross section area is constant. To obtain the maximum net power with fluid flow resistance, the optimal cross section area should be 0.0056 m(2), with the optimal scales at a height of 0.005 m, and length of 0.56 m, when applied in an automotive vehicle. Exchanger scales are available in a wide optimal design range to help achieve a high net power output, if the scale optimization match is met. (C) 2016 Elsevier Ltd. All rights reserved.