What a 500 kV Power Line Is

Electricity moves across California in tiers of voltage. Local lines run at 69 kV or below; the regional grid steps up to 115 and 230 kV; and at the very top sits 500 kV — “extra-high voltage,” the backbone that carries bulk power across the West. A single 500 kV line can move roughly 1,000 to 1,500 megawatts, enough for well over a million homes. ^{[1] [2]}

That capacity is the whole point of this project: the Golden Pacific Powerlink is a bulk transmission line built to move power between regions — by the grid operator's own account, to serve San Diego and the Los Angeles basin and connect remote desert renewables — not a local line built to serve Temecula. ^[3]

A 500 kV line is not a taller version of the wooden poles along the highway. It rides on steel lattice towers that here would stand 180 to 200 feet — taller than a 15-story building — across a cleared right-of-way on the order of 250 feet wide. ^{[2] [4]}

That scale is why the comparison SDG&E draws — that it would merely “co-locate” with the 1930s 69 kV line on roughly 50-foot wooden poles nearby — understates what is being built. The U.S. Department of Energy notes a structure's size scales with its power rating; a 500 kV tower dwarfs a 69 kV pole. ^[1]

High-voltage power lines have started some of the worst fires in California history. The state auditor found that power lines caused six of California's twenty most destructive wildfires since 2015. ^[5]

The deadliest was the 2018 Camp Fire — ignited by failed hardware on a PG&E high-voltage transmission line — which killed 85 people, destroyed nearly 19,000 structures, and pushed PG&E into bankruptcy, even though the company had flagged that line's “high” failure risk years earlier. Southern California Edison's lines sparked the 2017 Thomas Fire, and SDG&E's own lines caused the catastrophic 2007 fires covered on our wildfire page. The state's own regulator notes utility equipment causes a small share of fires but roughly half of the most destructive ones. ^{[5] [6]}

Beyond fire, extra-high-voltage lines carry effects the environmental review has to examine. In wet weather the conductors “corona” — an electrical discharge that produces an audible hum, radio and television interference, and small amounts of ozone — and the lines' fields can induce currents in nearby metal such as fences and pipelines. That is the documented basis for residents' reports of interference with electronics and appliances. ^[7]

These overlap the concerns detailed on our other pages — audible noise, electromagnetic fields, and night-lighting — and, stacked with the fire, water, habitat, and property impacts, are why a line of this class draws the scrutiny it does.