Cities Skylines Hydroelectric Power Plants (Dams) Guide

Build the Dam in Cities Skylines.

Hydroelectric power plants or Dams in Cities Skylines are one of the most efficient systems to generate electricity. Dams will produce the second-highest power output and have the second-cheapest weekly upkeep, provided they are correctly constructed.

The only Power plant that beats them is the Fusion Plant, which you acquire after 65k population. For the time before that, you’ll need to rely on Dams for efficient, pollution-free, and cheap electricity.

For more help on Cities Skylines, read our Industry Management Guide, Beginner Tips and Zoning Guide.

How Dams Work in Cities Skylines

This game has an annoyingly realistic way of simulating the structure and function of dams and also the flow of water. Of course, it’s not asking your CPU to calculate complex transient flow equations, but it’s realistic enough for you to get confused.

Dams work by filling a ‘reservoir’ with water and then unleashing it downhill. In some cases, the dam is not working because of the terrain in which it is constructed. This level difference between the reservoir and the release determines how much electricity you generate in Cities Skylines.

The reservoir is what you build at first, but some players call it the dam.

How to build efficient Dams in Cities Skylines

You can build dams after reaching the Small City milestones, as this unlocks the dam option. Once you get the option, select the location of your dam, and you are good to go.

In the game, water has a natural flow associated with its strength and speed. Whenever you click the Water infograph, it will display the general speed – lengthier arrows mean more speed.

You also need to consider the height of the water as well. Once you place a reservoir initially, it will attempt to store water on its ‘backside’. Do not forget to place the dam in the right direction. The direction of the arc should always be facing upstream.

For the best efficiency, you must cover the entire river bank. Once the water accumulates till the road part above it, it will release water from the other end.

Now, often, what will happen is that the reservoir will fill up till the road part and release the water, and your output in MW will increase. However, as the dam releases the water, its level on the storage side will begin to drop, and so will your power output.

This isn’t good for your city, mainly if it primarily relies on the hydroelectric dam in Cities Skylines. You’ll have regular blackouts, followed by periods of good electricity availability.

To gain consistency, you must keep two things in mind: the water speed and the dam’s height. These two, along with the width of the bank, will determine how much power you can generate.

Dam Placement and Height

The main part of the complexity arises here. The dam needs to be placed at a water level that has a balance between speed and height. Water in areas that are too high will not be as fast. At the same time, water in low-level areas will not have enough strength and potential.

It would be best if you found a balance between the two. Once you’ve determined the sweet spot, you must decide the dam’s height. A lot of times, players will make the mistake of levelling the height of the dam with terra firma and connecting the roads.

This is not a good idea, as the water will take too long to accumulate. You’ll often face problems such as the above-mentioned power fluctuations in Cities Skylines.

Instead, the dam’s height should be enough for the water to flow consistently. Unfortunately, there’s no real way to determine this height, as it is through trial and error.

Another thing you should keep in mind is that the initial power output value given to you isn’t exactly true. It may be smaller or much larger than it says, so don’t go on the game’s value when placing the dam. Instead, take note of the water flow and speed.

Sometimes, you’ll run across rivers with uneven banks. In such cases, you should always ensure that the dam’s height is relative to the lowest side of the river.

Water Control

In Cities Skyline, Water control should be taken seriously to prevent flooding. A great way to get your dam to have huge efficiency is to spray tons of water into it. How? It’s simple: make sure all your sewage disposal pipes are located behind the reservoir (the place where the water is accumulated).

This way, you’ll flood the hydropower dam with shit-filled wastewater, making it more efficient. Initially, it may not work well, but it will be a long-term investment, as the more the population grows, the more efficient the dam will become.

You can suck out all the water with water pumps at the place where the actual dam would be, and once it is low enough, you can place the dam there. Then, you can put an utterly opposite-facing dam 500 meters behind it. This will create a perfect reservoir that has been completely dried out.

Now, the next thing you can do is place all your sewage disposals in this reservoir and fill it up. This way, you’ll have a dam that runs on wastewater, whose efficiency improves as the population grows.

Dam Efficiency

When running at full capacity (1600 MWs), dams are the second-most cost-efficient power plants in Cities Skylines. The first is the very special Fusion Reactor, but that’s only after you’ve reached 65k population and unlocked the required unique buildings.

Even a dam running at half capacity (800 MWs) is more efficient than a Solar power plant. A hydroelectric dam running at a maximum of 1600 MWs costs a stupendously cheap $2 per MW per week. A fusion reactor, in comparison, is $0.5 per MW per week.

A hydroelectric dam at 800 MWs will cost you $4 per MW per week, almost twice as much as the third cheapest form of power (Solar), costing $7.5. However, there is also a wrong end to all this.

A dam operating at 400 MW will cost you half a dollar more per MW per week than a Solar Power plant. A hydroelectric power plant running at 200 MW is as expensive as an oil power plant ($16 per MW per week), while anything below that will cost you more than any other power plant type.

For this reason, it’s always a good idea to keep high output in mind when building dams, or you’ll just be hurting your income.

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Ali is a passionate RPG gamer. He believes that western RPGs still have a lot to learn from JRPGs. He is editor-in-chief at but that doesn't stop him from writing about his favorite video ...