Paul Chesser’s column today for the National Legal and Policy Center provokes that question. Chesser shows that “public records show the company [Apple] has received permits to install 44 pollutant-spewing diesel generators for back-up power” to its server facility in Maiden, N.C., served by its 100-acre solar facility. He writes:

The diesel generators for the western North Carolina data center are the normal redundancy you’d expect a power-dependent corporation to install to insure continual service (such as cloud computing and iTunes) for customers. But even though the back-ups will run for only a few hours a year (unless there’s a catastrophe), the fact that they’re fossil-fueled highlights how next-to-useless the “green” alternatives are. After all, have you heard of solar- or wind-powered backup generators?

See, it’s normal redundancy — i.e., normal if you’re talking about a power source that is nondispatchable. That’s a term to describe that power from solar or wind aren’t necessarily available when you want it (when a consumer turns on the switch expecting power to be dispatched there at that precise moment). Their availability depends on the cooperation of the natural elements of sunlight and blowing wind.

Nondispatchability, intermittency, or whatever term you give it, that’s what makes solar and wind more expensive (including the most expensive sources for curbing greenhouse emissions).

That’s also why state renewable energy portfolio standards (REPS) mandates are known rate hikers. They require a set percentage of inescapably more expensive energy in the mix of generation. The North Carolina General Assembly is currently debating capping and studying this state’s REPS mandate before it more than doubles.

It is also debating studying “known and measurable costs and benefits of distributed generation, including grid issues and standby generation issues associated with nondispatchable sources and unseen costs imposed by consumers not participating in net metering.”

Chesser’s report reveals why that aspect would be important:

Power generated by the 100-acre solar expanse – dubbed an “iSore” by the U.K. Daily Mail – is absorbed by Duke onto its grid at great expense, while Apple accesses nonstop, round-the-clock electricity at super discount rates. Net result: The rest of Duke’s customers pay more for having to accept additional solar into the mix, thanks to Apple.