Can we meet all our energy needs with renewable sources by mid-century?

The answer is most assuredly yes; anything is possible with unlimited resources. But the key question is always at what cost?

Some research suggests a 100 per cent renewable future is achievable at reasonable cost. In a high-profile 2015 study, researchers led by Stanford’s Mark Jacobson argued that the entire continental United States could be powered by water, wind and solar by 2050 at low-cost. The study excluded alternative technologies and fuels such as natural gas, biofuels, nuclear power, and stationary batteries. The study’s conclusions have garnered quite a bit of attention. Celebrities like Leonardo DiCaprio have cited it, and politicians armed with the study’s findings have introduced legislation mandating 100 per cent renewable energy in states like California.

Unfortunately, Jacobson et al.’s findings may not hold water – specifically, enough water to generate over ten times more hydroelectric output than will likely ever exist in the United States. That is just one of the critiques put forward by a new study published earlier this week, which launched the energy policy world into heated debate. The new study – led by former U.S. National Oceanic and Atmospheric Administration scientist Christopher Clack and co-authored by 20 other energy, economics and policy experts – finds significant modeling errors and implausible assumptions among other critiques of the Jacobson study. In particular, the Clack report points out that the original study relies on peak hydroelectric output in excess of 1,300 gigawatts to balance intermittent renewables – an implausibly large amount considering the original study assumes roughly 150 gigawatts of installed hydroelectric capacity.

I don’t want to go into detail on the new study’s other findings, but the original paper, critique and subsequent responses from Jacobson et al. and Clack et al. are worth reading, even if only for some insight into the world of academic debate. Instead, I want to focus on a larger, more existential debate this academic dispute set off – whether 100 per cent renewable energy is the goal we should seek to achieve as we design policy to mitigate climate change.

It’s hard to predict the future in the world of energy – especially in a carbon constrained future. New technologies are constantly emerging, and costs are constantly changing. It is possible that renewable technology breakthroughs will allow us to achieve our climate goals easier and at lower cost than anyone can currently imagine. But it is also possible that the next big “game-changing” solution will always be five years away. Other options, such as nuclear or carbon-capture technology, may be needed to achieve climate goals.

So should policy-makers today act as if the game-changing solutions are a guarantee as Jacobson et al. suggest? Some argue that it’s okay. Even if the potential for a fully renewable future is uncertain, plowing resources into intermittent renewables today is a no regrets option, at least until real reliability concerns start coming into play (see this tweet storm by Vox’s David Roberts for a longer, more nuanced argument).

There is some merit to this argument. It is highly likely that resources such as solar and wind will play a large role in a low-carbon future – especially at levels higher than today. They argue that policy focusing exclusively on renewables is okay because policy can always adapt later if technology and other circumstances necessitate a different path.

The issue with this line of reasoning, however, is that our energy system is a large and slow moving system. Research and development and investment cycles for energy infrastructure are often very long. Decisions made today can have wide ranging impacts decades down the road. In a system characterized by such high levels of uncertainty, policies designed to propagate specific technologies, as opposed to specific outcomes, could have the negative impact of locking out future promising solutions to the climate dilemma. Technologies that are not ready today, may be available in the future if investors and other market actors believe there will be a place for them.

For this reason, policy should reflect the long term and highly uncertain nature of the energy system. Claims that a certain pathway is the best pathway should be viewed with skepticism, as Clark et al. have shown. It is entirely possible that a 100 per cent renewable energy system will be the best way to achieve our climate goals by 2050, but it’s also possible that this is not true. We simply do not know the exact technological mix that is best.

Luckily, the one thing we do know is what we want our energy system to do. We want our energy system to continue to provide the high standard of living it has unlocked over the past century, but we want it to do it in a sustainable way. This means we must achieve this goal at the lowest possible cost, and the best way is policy that will allow any solution that can achieve this goal to succeed if the price is right.

Our policy should be geared towards getting the energy system to do what we want, and not dictating how it should get there.