Does Rooftop Solar Actually Help the Climate?

For a few weeks now, Heatmap’s staff writer, Emily Pontecorvo, has been trying to figure out if installing rooftop solar panels on your home actually reduces carbon pollution in a systematic way. In other words: If you own a home, and install solar panels on it, are you doing anything to change how much fossil fuel gets burned in your region or around the world? Or — somewhat counterintuitively — will your panels just increase the cost of electricity near you while shifting demand for those fossil fuels around?

On this week’s episode, we try to answer these questions in a satisfying way. Princeton Professor Jesse Jenkins and I welcome Emily to the podcast to discuss the messy truth of distributed solar power.

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Here is an excerpt from our conversation:

Emily Pontecorvo: My question is, if you're taking this solar-shaped hole out of electricity demand and that's displacing a cheaper utility-scale solar project, how do we go from that to you're not having an effect on emissions? Why is displacing that cheaper option than meaning that it's not as an effective climate action?

Jesse Jenkins: Well, because basically there's a certain amount of demand for solar-shaped production in the electricity system, right? And if you're reducing demand for electricity at exactly the time that a utility solar project would produce, then you're making the economics of building more solar incrementally worse as you add more distributed solar.

We still get basically the same amount of overall solar power in equilibrium. Like, you know, that's the amount that's profitable for people to invest in. It's just that you've shifted it from, again, cheaper projects at larger scale to more expensive projects at smaller scale, particularly in the U.S. We can come back to why the U.S. market is so, I think, broken and so much more expensive than it needs to be.

But particularly in the US, it is much more expensive, like three or four times more expensive, to build a megawatt worth of solar panels in 10 kilowatt increments at a bunch of different homes than it is to build one megawatt of solar on a big landfill or in a farm or on a big box store.

Pontecorvo : So is the idea that, do you get less solar overall or is it?

Jenkins : No, you basically get the same amount. You just get the same amount of solar and it's just more expensive.

Pontecorvo : Why does it matter then? I mean, obviously it matters. It's a better outcome to have a cheaper clean electricity system. But ...

Jenkins: No, it's a great question.

So why does it matter? I mean, there's two questions.

You were asking before, like, does it amount to an effective climate action? Well, if it doesn't increase the overall supply of solar power in the regional grid, then no, it's not an effective climate action.

It might be fine for you to do it as a personal decision for other reasons like economics or feeling like you don't want to keep paying your utility because you don't like the utility and you want to generate your own power. Like there's lots of other reasons why you might do this. Or because you want to save land, right? We can talk about the sort of land-saving potential distributed generation, which I think is probably the best case for it.

But in terms of climate impact, it's null. If you're not increasing the supply of clean energy overall, you're just substituting one clean megawatt hour for another clean megawatt hour.

Why does it matter that we're making that megawatt hour more expensive? Well, at the end of the day, we have to keep our electricity supply affordable as we decarbonize. Both because it's important for equity reasons, because we don't want people who have a hard time paying their bills to have to pay a lot more. But from a climate perspective, because we have to radically expand the amount of electricity supply and decarbonize transportation and heating and industry and make hydrogen and do all these other things, that are going to require electricity to be relatively competitive against the fossil fuels that they're trying to displace in those sectors.

This episode of Shift Key is sponsored by…

KORE Power provides the commercial, industrial, and utility markets with functional solutions that advance the clean energy transition worldwide. KORE Power's technology and manufacturing capabilities provide direct access to next generation battery cells, energy storage systems that scale to grid+, EV power & infrastructure, and intuitive asset management to unlock energy strategies across a myriad of applications. Explore more at korepower.com.

Music for Shift Key is by Adam Kromelow.