The Paris Palais des Congrès, a vast building comprising a Congress centre, a hotel and a shopping mall is equipped with an ice storage system allowing it to optimize its power-bill management in winter, but also to shave summer peaks and to generally improve the efficiency of its cooling systems. The system was installed in 1999, but had to be strengthened in 2004, in order to compensate for the heat produced by ever-increasing lighting. The initial system comprised three refrigeration systems providing water at 6-12°C (entry/outlet temperatures) with an overall capacity of 4 MW. It is completed with a 6000 kWh Fafco ice storage system operating with a 10.1 x 3.8 x 3.2 m tank. After the 2003 heat wave, a 3 MW McQuay refrigeration plant was added in 2004, along with a 7.6 x 5.1 x 3.65 m tank. Ice water plants represent an overall capacity of 17.5 MW. This potential amounts to 22 MW once ice discharging is taken into account. Ice-storage levels should take into account factors such as hotel bookings, the show and congress agenda and weather forecasts. In general, both ice-storage systems are loaded at levels of 70-80% during off-peak periods. In winter, when demand for cooling is lower, one ice-storage load is sufficient to provide for cooling needs for 2 days without having to operate the cooling system. The ice tanks are refilled at night during off-peak hours, when electricity is cheaper. In summer, when demand for cooling is higher, the ice-storage system makes it possible to avoid using electricity during peak hours by using the stored cold rather than the less energy-efficient option of operating an extra compressor at partial load. The system cuts the Palais des Congrès power bills by 15%.