Hey @dolmosm actually there is some operational cost of renewable energy, such as the upkeep of the turbines and employing engineers and mechanics. Although the running costs tend to be much less than a non-renewable generation as you don’t need to buy any fuel
The cost to us as your supplier to buy energy is the same for renewable and non-renewable as they are pooled together, so in fact, it ends up that greater renewable generation drives down the overall cost of wholesale prices.
What @sj_han meant by “underutilized renewable generation” is that a lot of renewable generation, being so quick to start up, is stopped from producing any energy into the grid if the grid is already at full capacity. It’s much easier to switch wind turbines and solar panels on and off that a coal-fired power plant that takes 14 hours and A LOT of fuel just to warm up and get going.
This is why sometimes on really windy days you’ll see turbines that aren’t even moving. Here’s a link that explains a bit more detail http://www.telegraph.co.uk/news/earth/energy/windpower/7840035/Firms-paid-to-shut-down-wind-farms-when-the-wind-is-blowing.html
So it all really comes down to the development of more dependable and predictable sources of energy or battery storage to help increase our capacity for renewables