The ECAT is a short form for Energy Catalyzer. It is basically a table-top fusion reactor, i.e. a fusor, that can produce nuclear size energy output at room temperature or temperatures close to room temperature.
The process utilized is called the Rossi Effect and is a proprietary of Leonardo Corporation with IP rights through the patent. A very small cylindrical reactor core (20cm x 5cm) is capable of producing kW sized output for a long duration of time (months) at negligible fuel cost.
This technology is revolutionary and the implications are vast. It will define the next era of energy production and render fossil fuels obsolete as it is cheap and 100% environmentally friendly.
The first generation of ECATs will primarily be used for heating.