Here are three reasons to like PV mounted on Denver houses, even though it's expensive:
1. Transmission losses - - Although grid-tied PV needs a functioning grid, most of the PV kilowatthours generated at a PV-equipped house stay in the neighborhood and aren't diminished by transmission losses which are usually quoted at 30%.
2. Autonomy - - Let's say you are building a spec house that you want to have low net energy usage. If you install PV, you have added value to that house. If Xcel invests directly in wind energy, that doesn't help you or your buyer.
3. Utility power outage avoidance - - Once PV market share reaches a crucial point, the Xcel will see the potential of outage avoidance that distributed PV inherently has. At that point they will start providing direct inverters and distributed batteries. Utilities receive big rewards for reducing outages.
In Colorado, Xcel is required by law to reach 30% renewable energy by 2020. Neighborhood PV is one of the top 3 ways this will happen, partly because it's easy and incremental compared to larger, more cost effective but cost intensive measures.
Is a Renewable Energy Portfolio Standard an artificial incentive? Of course it is, but until a carbon tax is implemented, there is no other incentive to reduce the use of fossil fuel.