On Towards the Stars: Power and Climate
[This post is part of a larger strategy guide for Civilization 6]
One thing that sets civ apart from other 4x games is its ability to continually introduce new mechanics as the game goes on. Flight, tourism, space race — these mechanics keep the game dynamic and fun, so that each turn you're thinking of doing something new. Power generation and climate change are both fairly late game mechanics.
Power
The power mechanic only really shows up in the late industrial era, and only becomes really important in the mid modern era. As a result, I really don't care much about power in 90% of my civ games. But when I get into that late game, when nukes start flying, power becomes really important.
Very broadly, powered cities give bonuses to tier 3 buildings in districts. Powered factories get +3 production, powered stock exchanges get +7 gold, and so on. The full list is here.
The trick with power is figuring out how to generate it. The game provides 4 ways to do so:
Power plants that burn coal, oil, or uranium;
Hydro-electric dams;
Renewable energy tile improvements;
Suzerain of Cardiff + Harbor buildings
TLDR: you're basically always going to generate your power from coal power plants.
To quickly go over the other options:
Oil reserves are critical for almost all late game military. While it's definitely possible to use oil for power generation, in general I'm so oil starved that I can't justify using any for power. By contrast, coal is really only useful in navy games where I am trying to build a lot of battleships.
Rarely, it makes sense to use hydroelectric dams. The dams are a comparably early source of power and can offset some of your coal consumption if you need coal for ships/railroads. But they do cost a chunk of production and only give power (unlike power plants which give additional production bonuses).
Most of the rest of the options either come way too late in the game (renewables, uranium) or rely on a specific setup (Cardiff harbors).
The last thing to note here is the production bonuses on coal power plants, especially compared to oil or uranium. Coal plants double the adjacency bonus for the industrial zone. In a well planned industrial zone, that could easily be +16 production (roughly +8 from placement, doubled if running the right policy cards). Oil and uranium plants give lower production (+3 for oil, +4 and +3 science for uranium respectively) but they give them to all cities within 6 tiles. The math maybe sounds nice for oil/uranium. Maybe it's easier to get a bunch of cities close by, compared to getting really high adjacency industrial zones. But generally you really do want one really high production super city to do things like pump out units or build rockets. Pound for pound, marginal production improvements across the empire are less useful than one big burst in one place. (Also, more often than not, I just end up building a ton of coal plants in all my cities.)
I think you could make a case for oil/uranium plants, but it's in really rare situations where you don't have a lot of nearby industrial zones but do have a lot of nearby cities. Maybe if you're playing a culture game or something.
Climate
The primary downside of power generation, and especially coal burning, is the increase in carbon emissions and the resulting flooding of coastal tiles + increase in natural disasters. These are potentially bad effects, but they importantly impact everyone equally. This creates a prisoner's dilemma — anyone who doesn't go for coal loses out on production against everyone else who does, and if anyone goes for coal everyone gets the same negative effects.
And in fact, the folks who have higher production often are better suited to withstand the effects of climate change. They can create more builders to repair pillaged tiles, or build out flood barriers earlier. In other words, there's actually a slight positive pressure for people to try and increase the amount of climate change that's occurring, to try and drag down everyone else who can't cope.
So I think most people who play multiplayer just build a bunch of coal plants and call it a day, climate change be damned.
The one exception is if you are going for a diplo victory. Having a ton of carbon emissions results in a direct penalty to your diplo favor generation (-1 favor for every 3 pollution points higher than the average, capped at -20). Emissions also outright prevent you from winning some scored competitions, which are often vital for a diplo victory. In these cases, it's possibly worth delaying production bonuses by eschewing coal plants. But you have to be pretty sure you're going to win soon, because every turn that passes is a turn that your opponents will out produce and out ramp you.