Hydropower is moderately expensive compared to the cheapest renewables but remains one of the most cost-effective energy sources over its full lifetime. New hydropower projects average about $0.057 per kilowatt-hour globally, which is higher than onshore wind ($0.034/kWh) and solar ($0.043/kWh) but competitive with or cheaper than most fossil fuel plants. The catch is that hydropower costs heavily depend on scale, location, and the enormous upfront investment required to build dams and powerhouses.
How Hydropower Compares to Other Energy Sources
The most useful way to compare energy costs is the levelized cost of electricity, which divides the total lifetime cost of a power plant by its total lifetime energy output. In 2024, IRENA found that the global weighted average for new hydropower came in at $0.057 per kilowatt-hour. That’s roughly 68% more than onshore wind and 33% more than solar PV. So if you’re comparing it strictly to the cheapest renewables available today, hydropower looks expensive.
But that comparison misses something important. Wind and solar only generate power when conditions are right. Hydropower with a reservoir can store energy and dispatch it on demand, functioning like a giant battery. That flexibility has real economic value that a simple cost-per-kilowatt-hour comparison doesn’t capture. A grid relying heavily on wind and solar still needs something to fill the gaps, and hydropower does that without burning fuel.
Why Upfront Costs Are So High
The single biggest factor that makes hydropower look expensive is the capital cost of construction. According to U.S. Energy Information Administration data, the average overnight capital cost for a conventional hydropower project in the United States is about $3,090 per kilowatt of capacity, but that figure varies wildly by region, from roughly $1,456/kW in the cheapest areas to $5,507/kW in the most expensive. Compare that to solar farms, which can be built for well under $2,000/kW in many cases.
Several factors drive those high construction costs. Every hydropower site is unique, requiring custom engineering for the local geology, river flow, and terrain. You’re building massive civil infrastructure: dams, tunnels, spillways, and powerhouses. Environmental compliance adds another layer. Projects in the U.S. spend an average of about 14.6% of their total budget on environmental permitting and studies, and that percentage can climb to 25% for smaller projects. Fish passage systems, habitat restoration, and water quality monitoring all add to the bill.
Permitting timelines make things worse. In the U.S., obtaining an original hydropower license takes an average of 5 years, and relicensing an existing project takes about 7.6 years. Every year spent waiting is a year that financing costs accumulate on a project that isn’t generating revenue. For a capital-intensive technology like hydropower, those delays can significantly increase the final price tag.
Small Projects Cost More Per Kilowatt
The size of a hydropower project has a major effect on cost. Large hydropower plants with storage typically cost between $1,050 and $7,650 per kilowatt to install, while small hydro projects (generally under 10 MW) range from $1,300 to $8,000 per kilowatt. Very small installations below 1 MW can run from $3,400 to over $10,000 per kilowatt.
This scaling effect is common in energy infrastructure, but it’s especially pronounced in hydropower because you still need site-specific engineering, permitting, and civil construction even for a small project. The fixed costs don’t shrink proportionally with the plant’s output. If you’re evaluating a small community hydro project, expect the per-kilowatt economics to be significantly less favorable than a large dam.
Where Hydropower Saves Money: Operations and Lifespan
The upfront cost is only part of the story. Once built, hydropower is remarkably cheap to run. Annual operations and maintenance costs typically stay at or below 2.5% of the original capital investment. There’s no fuel to buy, ever. The “fuel” is flowing water, which is free.
The real economic advantage of hydropower is longevity. A well-built and properly maintained dam can last 100 years or more. That’s two to three times the lifespan of a solar farm or wind turbine. Over a century of operation, the high upfront cost gets spread across an enormous amount of electricity generation, which is why hydropower’s per-kilowatt-hour cost stays competitive despite the expensive construction phase.
The dam and civil structures last the longest, but the mechanical and electrical components inside need periodic replacement. Turbine governors last about 30 years. Gates and their motors need replacing after 30 to 50 years. Penstocks (the large pipes that channel water to turbines) last 40 to 60 years. Electronic control systems may need updating every 20 years or so. These refurbishments cost money, but they’re far cheaper than building a new plant, and each round of upgrades can also improve efficiency.
The Real Cost Question Depends on Context
Whether hydropower is “expensive” depends entirely on what you’re comparing it to and what you need from your grid. If your only criterion is the lowest possible cost per kilowatt-hour for new generation capacity, onshore wind and solar are cheaper today and getting cheaper every year. Hydropower can’t match them on that metric.
But if you need reliable, dispatchable power that can ramp up in minutes when demand spikes or the wind dies down, hydropower competes with natural gas peaker plants and battery storage. In that comparison, it often wins on cost, especially once the plant has been operating for a few decades and the construction debt is paid off. Many of the world’s existing hydropower dams were built decades ago and now produce some of the cheapest electricity available anywhere.
Geography matters too. Countries and regions with favorable topography and water resources, such as Norway, Brazil, or the Pacific Northwest of the United States, get hydropower at costs well below the global average. In flat terrain with limited water flow, the economics may never work. The wide cost range ($1,050 to $7,650 per kilowatt for large projects) reflects this reality: a hydropower project in the right location can be a bargain, while one in the wrong location can be a financial sinkhole.
For existing plants, the economics are clear. A dam that’s already built and paid for produces electricity at very low marginal cost, often just a few cents per kilowatt-hour for maintenance and operations. The expensive part is building new hydropower, and even then, the 50 to 100 year payoff window makes it a different kind of investment than solar or wind, one that future generations will still be benefiting from long after the initial cost is forgotten.