I've seen residential units in the 5 KW range available from other vendors. It seems pretty simple to scale this technology to different sizes. The 1 KW unit is too small to be much good in a typical American household but it could easily be scaled to 3-10 KW. The size depends on sustained verses peak loads. There are a lot of things in a typical household that draw a surprising amount of current, such as hairdryers (1500 watts), clothes dryers, and electric ovens. If you're looking for a unit to be completely independent of the power grid, then you'll want to see what you can do to reduce the peak loads. For example, you can use gas clothes dryers and stoves. If you're going to stay on the grid, much smaller fuel cells are practical. You just handle your peak loads by drawing electricity from the grid.

The 250 KW units could be suitable for neighborhoods or businesses. I wonder how their efficiency compares per kilowatt/hour with the smaller units. For most conventional generator systems, larger units are much more efficient than smaller ones. This might not be the case for fuel cells.

Plug Power

GE MicroGen

Northwest Power