Hydroelectric Power-plants in Cities Skylines are the most complicated Power-plants in the game. However, they are also the ones two produce the second highest power output and ones with second cheapest weekly upkeep, provided they are constructed properly.
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.
Cities Skylines Hydroelectric Power Plants
Here’s a guide for you go-green shouters about how Dams work in Cities Skylines, and how to get the best out of them.
How Dams Work Generally
Cities Skylines 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 a bit confused.
Dams work by filling a ‘reservoir’ with water, then unleashing it downhill. This difference in levels between the reservoir and the release is what determines how much electricity you generate in Cities Skylines.
The reservoir is what you actually build at first (the thing people commonly [mistakenly] call the dam itself).
In the game, water has a natural flow that is 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. The more the potential the water has, the better the dam will work when placed. Once you place a reservoir initially, it will attempt to store water on its ‘backside’.
For the best efficiency, you must cover the entire bank of the river. Once the water accumulates till the road part above it, it will start to release water from the other end.
Now, often what will happen is that the reservoir will fill up till the road part, release the water, at which time your output in MW will be a decent bit. However, as the dam releases the water, its level on the storage side will begin to drop, and so will your power output.
This is very bad for your city, especially if it primarily relies on the hydroelectric dam. You’ll have regular blackouts, followed by periods of good electricity availability.
In order to gain consistency, you need to keep two things in mind: the water speed, and the height of the dam. These two, along with the width of the bank, will determine how much power you will be able to 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 at areas that are too high will not be as fast, whereas water at too level areas will not have enough strength and potential. You need to find a balance between the two. Once you’ve determined the sweet spot, you’ll need to decide the height of the dam itself.
A lot of times players will make the mistake of leveling the height of the dam with terra firma, and connecting the roads. This is not a good idea, as it will take too long for the water to accumulate till the required level to be released, and you’ll often face problems such as the above mentioned power fluctuations.
Instead, the height of the dam should be enough that the water manages 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 either be smaller or much larger than what it says, so don’t go on the game’s value when you are 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 make sure that the dam’s height is relative to the lowest side of the river.
You should always consider though that the height of the dam is always more important than the height of the river, provided the water current is strong enough.
A great way to actually get your dam to have huge efficiency is to actually 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 literally be flooding the dam with shit-filled waste water, making it more efficient. Initially it may not work too well, but it will be a long-term investment, as the more the population will grow, the more efficient the dam will become.
Gradually increase the amount of sewage disposal pipes behind the dam over time. What this is doing is actually greatly increasing the strength and speed of the water, which in turn is improving the power output and efficiency of the dam.
With this in mind, you can perform a dirty (literally) trick.
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 place a completely opposite-facing dam 500-meters or so 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 waste-water, whose efficiency only improves as the population grows.
When running at full capacity (1600 MWs), dams are the second-most cost-efficient power-plants in Cities Skylines. The first is obviously 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. The cost of a hydroelectric dam running at 1600 MWs is 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, which is 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.
If you have a dam operating at 400 MW, it 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 else you’ll just be hurting your own income.
If you have any questions about dams, or any valuable information you’d like to add, please share with us in the comments section below!