With increasing cost for power generation opportunities for small scale power generation from waste heat have increased. The awareness of untapped resources such as local waste heat streams as well as the available range of technology and products to harvest such streams is increasing steadily though field data is scarce for applications below 100 degrees C entry temperature. ORC applications have a large number of open parameters and therefore require field data for correlation of models. This paper presents field data and analysis of an ORC power generation plant operating with NH3. The unit operates on waste heat from a Swedish pulp mill at an available temperature of 75 to 85 degrees C. Performance at varying heat source conditions and capacity is reported as well as an analysis of the particular investment case. The data was generated during a 15 day period and show a thermal efficiency of 8-9% at capacities from 50 to 100%. The results indicate a flat thermal efficiency from 20 to 100% capacity. Investment case analysis is based on a purchase model while the chosen economic model is a supplier own-and-operate arrangement supplying the mill with power at a predefined cost during an extended period of time. (C) 2012 Elsevier Ltd. All rights reserved.