The growing share of electricity generation from renewable energy creates difficulties in maintaining the balance of generation and demand. This is mainly due to uncertainties caused by prediction errors in renewable generation. In order to maintain power system security, the participation of demand side response to the balancing services such as operating reserve is critical. In this paper, the capability of smart appliances to act as operating reserves for the system operator is investigated. The smart appliances considered are washing machines, dish washers and tumble dryers equipped with communication modules. A novel framework is introduced which enables system operators to access demand response from smart appliances in a timeframe suitable for operating reserves. A mathematical model is developed to simulate appliances with multiple discrete power phases. The delay and interruption of appliances cycles are considered in the model. A multiple time-step simulation is introduced that assesses the load reduction from a number of households as a response to a reserve instruction which is modelled as a price increase with a short notification period. The results are used to estimate the available demand response from Great Britain (GB) households at any moment of the day. With a 20% penetration of smart appliances, the demand response can provide up to 54% of the operating reserve requirements of the GB power system depending on the time of day. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.