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Aug 10, 2023

The little

There are many good reasons to burn less coal: It’s polluting, expensive,

There are many good reasons to burn less coal: It's polluting, expensive, damaging to human health, and emits more carbon pollution than any other form of electricity.

But an oft-overlooked factor is that burning fuel to generate electricity is astonishingly inefficient. Major energy losses are an unavoidable consequence of converting heat into motion, which is how conventional power plants generate electricity. They typically burn coal or gas to heat water, which makes steam that spins the blades of a turbine that interacts with magnets to generate electricity. More than two-thirds of the energy in coal is vented off as waste heat in the multistep process of making electricity.

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By contrast, wind turbines, hydroelectric turbines, and solar panels skip the step of burning fossil fuels to heat water. Instead, a turbine powered by wind or water simply turns as the current of air or water flows by it. And solar panels convert the sun's energy into electricity using semiconductors. No steam is required for either process.

The major differences in efficiency are best appreciated visually. The animation below sums it up.

The efficiency of power plants is measured by their heat rate, which is the BTUs of energy required to generate one kWh of electricity. The Energy Information Administration lists the heat rate for different types of power plants, for each year since 2011.

Data for the amount of electricity generated by coal and renewables is from the Energy Information Administration.

Find more details and infographics on the efficiency of electric power generation in this article: Energy loss is the single-biggest component of today's electricity system.

Karin Kirk is a geologist and freelance writer with a background in climate education. She's a scientist by training, but the human elements of climate change occupy most of her current work. Karin is... More by Karin Kirk