Powerhouses
A desert nuclear plant, a coal plant on the plateau, a steam field, a mountain battery and an oil field. A story in 5 stops on the Wattlas map of the North American grid.
Palo Verde
West of Phoenix, out past the last of the suburbs, three reactor containments rise from the desert flats near Tonopah, and there is no river anywhere in sight. A reactor has to shed enormous amounts of heat, which is why nuclear plants are built beside open water. Palo Verde's builders went into the desert anyway and brought their water with them. APS calls Palo Verde the nation's only nuclear plant not located on a body of water. Every year it recycles more than 20 billion gallons of municipal wastewater to cool the plant, piped out from the cities of the Valley, so water that once ran down their drains ends up carrying heat away from three reactors. Units 1 and 2 entered commercial operation in 1986 and Unit 3 in 1988, with utilities from Arizona, New Mexico, Texas and California sharing the cost and the output. APS says that for more than 25 years Palo Verde produced more electricity than any other power plant in the country, enough for more than 4 million people. In 2024 the expanded Vogtle plant in Georgia passed it in capacity.
On the map: Palo Verde, in the Arizona desert, is 3,937 MW on the map, the second-largest operating nuclear plant on the map after Vogtle (4,530 MW). The US Energy Information Administration gives 4,210 MW.
Four Corners
Several of Palo Verde's owners had built a giant together once before, a few hundred miles to the northeast on the Colorado Plateau. In the early 1960s the cities of the Southwest were growing fast, and the cheapest power to be had came from burning coal right where it came out of the ground and sending the electricity away over long high-voltage lines. Four Corners was built on that plan, near Fruitland, New Mexico, on land leased from the Navajo Nation. APS finished its first two units in 1963 and a third in 1964, and a group of utilities reaching from Southern California to El Paso added two much larger units in 1969 and 1970. Coal came by rail from the Navajo Mine to the south, and cooling water from the San Juan River by way of the man-made Morgan Lake. Nearby San Juan Generating Station, across the river, followed the same model, and from its first unit in 1973 until it burned its last coal in 2022 the two plants worked side by side. The three oldest units at Four Corners are already gone, and APS has said it will leave the plant by the end of 2031. Solar panels have begun to go up on the plateau around the old plants.
On the map: Four Corners is a 1,540 MW coal plant in New Mexico, operating on the map. Nearby, San Juan Solar I adds 300 MW, from 2024.
The Geysers
Hunting grizzly bears in the mountains between Cloverdale and Calistoga one day in 1847, William Bell Elliott came upon great puffs of steam pouring from the hillsides and ran to tell his companions he had found the gates of hell. The vents were fumaroles, not geysers, but the name stuck, and a resort grew up around them that drew Ulysses S. Grant and Theodore Roosevelt. Four Corners burned coal dug from the plateau around it. Here the fuel was the heat of the earth, rising as dry steam from rock warmed by a magma chamber miles down. In 1922 John D. Grant drilled a well and lit the resort with it, but the pipes and turbines of the day could not stand up to the corrosive steam, and the project was abandoned. In 1955 Magma Power and Thermal Power drilled the first commercial steam well in Sonoma County, and Magma's B.C. McCabe arranged to sell the steam to Pacific Gas and Electric. PG&E needed a small turbine that could run on low pressure, and it found one of its own, scrapped a few years earlier when Station B of the Sacramento streetcar line was retired. Refurbished and set to work in Unit 1, the old machine began commercial operation on September 25, 1960, rated 11 MW net and built for less than $2 million, the nation's entry into geothermal power. The field grew into the largest developed geothermal complex in the world, 18 plants drawing on more than 350 wells. By the late 1990s the steam was running short, and the answer came from the towns below. Since 1997 treated wastewater, from Lake County and later from Santa Rosa, has been piped up into the mountains, some 20 million gallons a day, and injected to recharge the field, much as Palo Verde cools its reactors with the wastewater of the Valley. The Geysers produced about a fifth of California's renewable energy in 2019.
On the map: The map marks The Geysers as a historic grid site dated 1960. Geysers Unit 5-20, at 644 MW, is the largest geothermal plant on the map, ahead of Cerro Prieto in Baja California (570 MW).
Sources: ASME landmark brochure, Wikipedia, The Geysers
Bath County
A plant like Palo Verde or Four Corners runs best at a steady pace around the clock, while the people it serves spend a third of that time asleep. By the 1970s the utilities of the East had plenty of cheap power at night and too little at the afternoon peak, and deep in Virginia's Allegheny Mountains they set out to build a machine that could move one into the other. Construction at Bath County began in 1977. Crews raised two earth and rock dams on Back Creek and Little Back Creek, one reservoir about 1,260 feet above the other, and bored tunnels through the mountain to join them. When demand is low, six reversible turbines pump water uphill on power from the steady plants. When demand climbs, the water falls back through the same machines at as much as 13.5 million gallons a minute. Commercial operation began in December 1985, and the station became known as the biggest battery in the world. In August 2024 China's 3.6 GW Fengning station surpassed it as the world's largest pumped hydro plant. Dominion calls Bath County the largest in North America, and it balances the load for millions of homes and businesses across six states.
On the map: Bath County, in the mountains of Virginia, is 2,931 MW on the map, the largest pumped-storage plant on the map; Ludington, in Michigan, is next at 2,180 MW.
Sources: Dominion Energy, International Hydropower Association, Wikipedia
The Permian Basin
For a century the ground under West Texas and southeast New Mexico has sent its fuel out to the rest of the country, and lately the Permian Basin has also become one of the grid's great customers. Since the shale boom the Permian has been the most productive oil field in the country, and as it grew its operators began running their pumps and compressors on electricity from the grid, while the towns that house their workers grew too. The load climbed faster than West Texas wires had ever been asked to carry. A 2023 Texas law, House Bill 5066, required a reliability plan for the Permian Basin to support that electrification, and the plan was approved in October 2024. How to build it was the harder question, and on April 24, 2025 regulators answered it by going past ERCOT's 345 kV standard to approve its first extra-high-voltage (765 kV) lines. Gas from this ground still fires much of Texas, and now ERCOT is building the biggest lines in its history to carry power back to it.
On the map: Oil and gas fields cover West Texas and southeast New Mexico, with plants and lines running through them. The map has 224 oil and gas field areas in all.
Sources: American Public Power Association, PUCT