In the residential sector, heat pumps are applied for domestic hot water and space heating. Simulations are widely used for general research in the field of heat pumps and to some extend to plan such installations. The advantages are low expenditure of time and costs compared to laboratory or field tests. Validation of simulation models is mandatory to guarantee a sufficient quality. In the presented paper, the field monitoring results of five ground-source installations are utilised for the validation of a black-box heat pump model. The model is similar to TRNSYS Type 201, but implemented in IDA ICE and then modified to handle the difficulties caused by non-standard mass flow and rampant polynomials. As overall result, deviations between 1% and 32% regarding modelled and measured efficiency are seen on monthly basis. The overall result appears as convincing, taking into account typical inaccuracies of laboratory and field tests as well as tolerances during heat pump production. As a side effect, the influence of standby consumption was quantified. For the five presented installations, standby amounts to fractions between 2 and 5% of the annual electricity consumption of the heat pump units. (C) 2014 Elsevier B.V. All rights reserved.