Flexible consumption devices are often able to quickly adjust the power consumption making these devices very well suited as providers of fast ancillary services such as primary and secondary reserves. As these reserves are among the most well-paid ancillary services, it is an interesting idea to let an aggregator control a portfolio of flexible consumption devices and sell the accumulated flexibility in the primary and secondary reserve markets. However, two issues make it difficult for a portfolio of consumption devices to provide ancillary services: First, flexible consumption devices only have a limited energy capacity and are therefore not able to provide actual energy deliveries. Second, it is often difficult to make an accurate consumption baseline estimate for a portfolio of flexible consumption devices. These two issues do not fit the current regulations for providing ancillary services. In this work we present a simple method based on the existing ancillary service markets that resolves these issues via increased information and communication technology. The method allows an aggregator to continuously utilize the markets for slower ancillary service to ensure that its portfolio is not driven towards the energy limitations resolving both the baseline issue and the energy limitation issue. (C) 2014 Elsevier Ltd. All rights reserved.