While distributed solar can’t solve the region’s transmission woes alone, Idaho and Washington would be smart to follow Oregon’s lead in boosting it for a cleaner future.

To meet climate targets, the Northwest needs to build unprecedented amounts of wind and solar power and the electric transmission lines to carry it. Easier said than done.

Utility-scale renewable projects—like acres-large solar installations or miles-long corridors of wind turbines—and the electric wires that connect them to cities and towns increasingly inspire opposition. They can require vast tracts of land, and, if not planned responsibly, can threaten sensitive habitats, prime farmland, and tribal rights.

In light of these challenges, some advocates argue that the region could avoid building transmission lines and large renewable projects if it instead dramatically scaled up what is known as “distributed solar.” Unlike their utility-scale counterparts, distributed solar projects generate electricity close to where it is consumed—say, on home and business rooftops, over parking lots, on small, unused fields—and bypass the transmission grid altogether. Distributed solar typically ranges in size from small, 0.001 megawatt (1 kilowatt) projects to medium, roughly 5-megawatt (MW) projects. For comparison, utility-scale solar farms in the United States tend to have installed capacities of 100 to 200 MW. The biggest farms in the country top 500 MW.

Unlike other parts of the United States, though, distributed solar has limited potential to offset the need for new transmission capacity in Cascadia. That’s in large part because most places in the region that are on the receiving end of transmission constraints need most of their power in the winter, when the sun is weakest. The biggest exception is southern Idaho, which, with its strong sun and high demand for summer power to irrigate farms, could be a prime candidate for scaling up distributed solar.

Even so, distributed solar, especially when combined with storage, can help decarbonize Cascadia. Local generation helps the region hedge against the risk that we simply won’t build new transmission lines and utility-scale renewable projects fast enough. But the Northwest is lagging in installing the most promising type of distributed solar infrastructure: midsize projects in the range of 1–5 MW. Idaho and Washington are especially behind. Policymakers in these states would be smart to lift project size limits to net metering and look closely at community solar, which has catalyzed midsize solar growth in other states, including Oregon.

DISTRIBUTED SOLAR HOLDS THE MOST POTENTIAL FOR OFFSETTING TRANSMISSION BUILDOUT IN THE FEW “SUMMER PEAKING” PARTS OF CASCADIA

In the Pacific Northwest, as elsewhere, more transmission capacity is needed to 1) meet rising electricity demand associated with electrifying everything from cars to stoves and 2) replace the supply of power that today comes from burning gas or coal. We’re especially short of transmission lines to bring clean power to cities and towns in western Oregon and Washington and southern Idaho. The argument that distributed solar can prevent transmission buildout is that by producing more power close to the people who use it, you won’t need to generate as much far away and thus won’t need to build transmission lines. Plus, you’ll lose less electricity in transit.

Indeed, in 2018, California’s independent grid operator recommended canceling 18 transmission expansion projects to save $2.6 billion. It cited reductions in projected electricity demand thanks to increasing levels of rooftop solar and energy efficiency. (And note that distributed solar isn’t the only way some places could prevent or defer building transmission lines. Others include upgrading existing lines, increasing energy efficiency, rolling out demand response programs, and installing distributed storage—all with different potential in different locales. These are not the focus of this article but are...