In the above description of the 2-stage machine, the terminology and description are somewhat mixed up. The 1st stage that the snow encounters is the auger, which is the corkscrew/spiral thingy that collects the snow and directs it towards the 2nd stage, which is the impeller. The impeller is basically a centrifugal fan that hurls (impells) the snow up the chute. It is similar to the impellers in leaf vacuums/blowers, grain harvesters, and centrifugal water pumps.

In a large single-stage snow blower, the center of the spiral auger has axial vanes that serve as an impeller of sorts. The auger and impeller are a single rotating part, and because of this, the auger must spin quite quickly, lest the vanes fail to throw the snow far enough out of the chute. Also because of this combination of functions, the whole rotating part might be called the impeller. This nomenclature is most appropriate for small single-stage snow blowers (snow brooms) that lack a spiral auger-like portion on the rotating part.

Compared to a small single-stage, impeller-only machine, a 2-stage machine adds an auger as stage 1. Compared to a large single-stage machine that has an auger, a 2-stage machine adds a separate, purpose-built impeller as a 2nd stage. Thus in a 2-stage machine, the auger and impeller can rotate at speeds suited to their respective functions.

I landed on this site in a search for consumer opinions and information on the Ariens AMP-24 electric snow blower. As far as I’ve seen, it is the only electric 2-stage snow blower, and it is also the only rechargable battery-operated model, so no messing with extension cords. But I don’t want to buy one without seeing how well it compares to gas-powered 2-stage snow blowers.