OTEC Works. The Seawater Flow Is The Problem.

Ocean thermal energy conversion, or OTEC, generates electricity from the temperature gap between warm tropical surface water and cold water pulled from about a kilometer down. The idea works: a plant off Hawaii has sent power to the grid before. The catch is scale. Because the temperature difference is small, the technology only converts a few percent of that heat into usable electricity, so producing even a modest amount of power means moving huge volumes of seawater. A 100-megawatt plant would need roughly 705,000 liters of water every second, pulled through an intake pipe about 10 meters wide and a kilometer long, built to withstand ocean currents, storms, and corrosion.

That infrastructure burden, not the physics, is why OTEC has never become a mainstream power source despite decades of testing since the 1970s. While solar, wind, and batteries have scaled into the hundreds of gigawatts installed each year, OTEC has stayed stuck at the demonstration stage, without the larger plants, repeat orders, and standardized equipment that usually follow a technology's commercial success.

For homeowners, this isn't something to act on. OTEC only makes sense in narrow situations, such as a steep tropical island where very deep, cold water sits close to shore, electricity is costly, and land is tight. Even there, it competes with solar, batteries, and other local options. It has no bearing on typical home energy upgrades or rebate programs.