Distribution is generally a monopoly, generation is not.
And "less than they pay for utility power" is a very, very high bar. Installation of a parallel grid, storage, and solar collection? Ignoring the grid, most solar companies I work with will contract to use your rooftop and install a solar system to tie into your grid-based power. You agree to pay $0.30(!) per kWh for all the generated power, they maintain the system. The cost of energy is fixed for the life of the contract (usu 20-30 years), and that's how the financing of the project is secured.
It's all find and dandy, but to break even you have to assume a large annual increase in local electricity cost (>10% inflation every year iirc). That's a pretty big bet to make, and one that relatively few companies are taking for cost reasons.