The public is repeatedly told that wind and solar are “free” energy sources. Of course, this statement relates to costs once the plant is constructed and operating because, like hydropower, there is no ‘fuel cost’ with wind and solar power as there is with fossil fuel and nuclear generating technologies. But even that statement is a bit misleading, for intermittent technologies like wind and solar cannot be relied upon to produce power when needed, and must have other technologies to back them up. The cost of the back-up power, usually gas-fired or coal-fired generation, is not added to the cost of wind and solar power, so the public is less aware of the issues of using these intermittent technologies.
