The nova spin is an electric generator that stores and makes kinetic energy. It makes energy by first using excess electricity of the house to spin a heavy metal rotor, then using the initial energy that it made from that spin to keep spinning itself and the house that it connected to. It can deliver full power output almost instantaneously without any consumption of fuel ( 500 megawatts)
Since it is electric and uses the energy that it creates to power itself so it requires 0 fuel, compared to a normal gas generator that uses about a gallon of gas per hour. Gas generators last about 14 hours on one tank and has to be replaced every 8 years, while the nova lasts 25 years without having to be replaced. Another benefit of the spin is that it can work in any weather and it avoids the aspects of chemical batteries polluting our planet.