Why do utility companies sometimes offer incentives for having equipment that uses less of their product?
The utility company wants to reduce PEAK demand -- it is much cheaper to ensure that power demand never goes above X than to build a new power plant.  Furthermore, balancing the peaks and valleys of demand means that they can generally use cheaper power sources (nuclear/hydro) and avoid the expensive gas/oil fired plants.

A washing machine has a giant heater in it, and a front-loader uses less water and thus less heat to heat it up.  Hence the utility no longer has to plan for so much more peak demand...