You have probably noticed that I tend to focus a lot on today’s technology rather the big breakthrough around the corner.

Part of this is for obvious reasons: I want to show we can get off fossil fuel even with conservative assumptions. Also, while we know what is possible, and even have good guesses as to what can be cheaper, we can’t know the timing.

But there is another reason.

We want to be very careful in constraining our future. Picking winners is always dangerous — you can promote unintended consequences, or even help kill a more promising technology. But you don’t want paralysis by analysis either. We do have an emergency situation. What makes sense is to follow a no-regrets path, as far as possible. Beyond that, follow the path that offers maximum choices — while understanding that we must make choices, and as human beings won’t always make the optimum ones. So ultimately, while we would like the best answers, it’s better pick ones that will work well enough than wait forever for perfection.

Efficiency contributes no matter what technology provides the energy supply. Even if consumption increases, better efficiency lets you use more expensive sources. Storage is good because there is no form of electricity generation that cannot benefit from it. Long distance transmission lines are good because they reduce the need for storage or backup if we use variable sources to generate electricity. (Storage is good, but transmission is almost always cheaper.)

But for every efficiency technique, there is another “just down the road” that will provide better efficiency. For every type of renewable supply, there is breakthrough “only a year away” that will do the job more cheaply.

Problem is, breakthroughs can stay “just down the road” for hundreds of miles and “only a year away” for decades.

We are pouring greenhouse gases into the atmosphere now. Start putting the things we know how to do in place. We won’t replace fossil fuels all at once, regardless. So if something better comes along before we are done, we switch new capital investment to that — and live with obsolete but working renewable and efficiency techniques until more primitive renewables wear out, as the price of having shut down some coal plants decades sooner than if we had waited.