How Does Solar “Take Cars off the Road”?

April 24th, 2015 by Susan Kraemer

As a CleanTechnica reader, you’ve likely come across this: “The greenhouse gas reductions of this solar project is the equivalent of taking X cars off the road.”

“Going solar with us is the equivalent of taking 28,953 cars off the road.” Or “This 400 MW solar project is the equivalent of taking 147,897 cars off the road.” Or whatever.

Sorry, no. Pleasant thought, but completely beside the point. No amount of solar capacity is going to empty our roads of cars. Forget cars. This or that solar project takes houses off the grid.

It is mystifying how this dumbed-down greenhouse gas reduction metric came to be so widely used.

Getting houses off the grid is the far bigger deal in terms of GHGs than cars. Cars are not nearly the greenhouse gas problem that electricity is, because we are already moving towards EVs.

In most states in the US, utility-scale electricity produces more CO2 emissions than cars do. Even California has far too much natural gas providing electricity.

Cars off the road obscures the real benefit

The worst thing about this odd metric is that the solar project that makes enough electricity for, say, 100,000 houses actually is taking something off the dirty grid — 100,000 houses.

Those 100,000 or however many houses are now running on solar, and will be for at least the next 25 years, and very likely forever.

Most utilities that are signing contracts with solar or wind developers for 20 to 25 years have now begun to sign the second rounds of contracts for the next 25 years when the first is over.

Just as old coal plants get retrofitted and upgraded and carry on running, old solar plants and wind farms have started to be retrofitted and upgraded and carry on running.

Two examples are right in California. The old turbines installed in the Altamont Pass in the 80s and 90s are being retrofitted with fewer but larger turbines, and have new 25-year PPAs with California utilities. The oldest utility-scale solar farm in the world, the SEGS project from BrightSource brains at Luz, began its 2nd round of contracts with California utilities in 2013.

This is because a good wind or solar resource doesn’t move around geographically. The windy or sunny regions now will also be windy or sunny regions at the end of their 25-year contracts in 2030, 2055, 2080, and so on. This geographic fact virtually ensures that both solar and wind contracts will simply renew four times a century, probably pretty much indefinitely.

So you can think about it this way: “such and such” solar project generates enough megawatt-hours of power a year to take 100,000 houses off the grid for at least 25 years, and perhaps for centuries. That is a clean comparison.

And as we add more solar and wind projects, you could say they will take coal plants and natural gas plants off the grid.

But likening renewable projects’ benefits to taking cars off the road implies that we must give up something — using cars to get around — rather than simply make the switch from using dirty energy to using clean energy.

Taking a coal plant off the grid — well, meh. That is the utility’s problem. Yeah, they’ll have to replace it with clean power, but that doesn’t change things for me. But take my car off the road? Uh… I don’t think that solar project is such a great idea after all. It is almost as if the scariness of the analogy is intentional. But in any case, it is simply dumb.

The “taking cars off the road” analogy feeds into the Rush Limbaugh–fed fear of the Eco-Nazi as someone who is just itching to take something away from me: my car! Those commies in China apparently did actually enforce a “cars off the road” ban, preceding the Olympics in Beijing.

I’m sure Frank Luntz loves it that our side stumbled on this dumb talking point. But it is not even accurate. Buses, trains — and even bad drivers — take cars off the road. But wind or solar projects help reduce emissions from electricity use.

If we want to make analogies to hammer home more viscerally the very real greenhouse gas benefits of solar or wind energy, why not use an analogy that has some truth.

Take this fact, for example. We know that Iowa now provides 27% of its electricity from wind. So Iowa in a sense is supplying everything that runs on electricity in the state with wind power for just over a quarter of every year, right?

So, you could say: Iowa gets 27% of its electricity from wind. “That’s like the equivalent of running the entire state 100% on wind power from January till the middle of April every year.”

That’s a metric that would at least make sense.









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