In this paper, the primary energy consumption and the economic viability of a combined heating, cooling and power (CHCP) system are derived. The focus is on small-scale applications in the range below 100 kW(H)/70 kW(C)/58 kW(el). CHCP is discussed between the boundaries of combined heating and power (CHP) and combined cooling and power (CCP) using a lumped parameter model. The method used is independent of a specific load profile for a building; only the full-load hours for heating and cooling are needed to predict the economic viability. German data is used for the example. A sensitivity analysis reveals the parameters with the highest impact on the primary energy consumption and the energy costs. The primary energy factors, the energy prices and the electric efficiency of the CHP are the dominating parameters. Increasing electricity prices favour the introduction of CHP and CHCP systems whereas increasing gas prices inhibit it. The energy cost analysis is extended to an economic analysis taking maintenance and investment costs into account. One result of this paper is a simple diagram which shows how many annual operation hours are needed for heating and cooling with CHCP to be more economical than a reference system. (C) 2010 Elsevier Ltd. All rights reserved.