That was the not so subtle message from the recently released NREL Western Wind and Solar Integration Study confirmed what many have been saying for years—there are no significant impediments to integrating wind and solar renewable energy into the power grid. The NREL study went further saying that it is operationally possible to add up to 30% wind energy and 5% solar energy share to the power generation mix.
Achieving this objective still requires work and change. Utilities must cooperate and improve coordination of their power operations across the grid to accommodate the intermittency of renewable generation for wind and solar energy.
Bonneville Power Administration and some other transmission owners have resisted such changes or even charged fees for integrating renewables into the grid well above their actual costs. Those old habits also appear to be subject to changes ahead as the market participants adjust to new realities since the NREL study found existing transmission capacity more than adequate to take all this renewable generation without as much new transmission build as transmission owners wanted.
For several years, our WECC power markets team at Global Energy Decisions asserted that transmission congestion was not an impediment to integrating renewables, now it appears that the NREL study confirmed their market analytics judgment. To be sure there are still congestion points on the power grid and need attention, but the main message is better integration and better collaboration are the key to scalable growth of renewable resources.
As a politically correct added bonus greenhouse gas emissions will be reduced by 25% to 45% if renewable energy market share grows to 27 percent of their electricity demand from wind and solar energy sources. The study says emissions costs would fall by 40 percent, depending on the future price of natural gas, by adding more diverse renewable resources and reducing the need for back-up generation typically natural gas-burning plants.
The NREL WECC study and its companion Eastern Wind Integration and Transmission Study both live into the 2008 US DOE study asserting that wind energy could reach 20% market share without adverse affects on the grid. 
Renewable energy is mainstream by almost every metric except one. No mainstream resource is sustainable as long as it depends upon unsustainable subsidies, feed-in-tariffs and other policy actions that force the ruthless competition of the markets to assure that ratepayers and investors have a least cost, best fit portfolio that is both affordable and sustainable.