Wind turbines and solar panels are lower-emissions than fossil fuels overall

Wind turbines, solar panels, and other low-carbon sources of electricity don’t produce significant greenhouse gas emissions during operation – this is the key distinction separating them from emissions-intensive fossil fuel power plants.

Nevertheless, wind turbines and solar panels in today’s world aren’t entirely emissions-free. Extracting their raw materials and building them comes with a greenhouse gas footprint. Opponents of wind or solar power often stand upon this fact to claim that they produce more greenhouse gas than scientists think or to question whether renewable energy is green. These are common kinds of claims, pushed by well-known renewable energy skeptics like Michael Schellenberger and groups like the anti-wind-turbine campaigners Stop These Things. So, how significant are these emissions?

As we’ll see below, solar panels and wind turbines have significantly smaller emissions footprints than fossil fuels. The numbers do tell us that it’s more greenhouse-gas-intensive to build solar panels or wind turbines than it is to build coal or gas power plants of the same energy capacity. But they also tell us that the vast majority of a fossil fuel power plant’s emissions comes from burning fossil fuels during its life – these emissions dwarf those from any kind of power plant construction. Let’s look at what those numbers say.

Life cycle analyses are clear: wind and solar are far less emissions-intensive than fossil fuels

To create a full picture of a power source’s emissions, we want to look at emissions from across that power source’s entire existence, also known as life cycle emissions. We don’t just count the emissions created while generating electricity – or not created, in the case of solar panels and wind turbines. We also count emissions associated with things like building the power plant, staffing it, and dismantling it at the end of its life.

These ‘cradle-to-grave’ studies are part of a well-established field known as life cycle analysis. Researchers are well aware of these non-production emissions – in fact, the purpose of life cycle analysis is to account for those very emissions, even when they’re not obvious.

Researchers from the U.S. National Renewable Energy Laboratory (NREL) pored over hundreds of published studies analyzing the life cycle emissions of various electrical sources, both renewable and non-renewable (Figure 1)¹. They averaged their results to present the amount of CO₂ equivalent each source would produce for every kilowatt-hour of generated electricity – enough to power the average U.S. household for about 50 minutes. Since the figures represent the same amount of energy, we can use them to make a fair comparison between sources.

NREL’s results are clear: wind and solar are far less emissions-intensive than their fossil fuel counterparts, even over their entire life cycle. They found wind turbines responsible for 13 grams of CO₂ equivalent on average per kilowatt-hour and solar cells for a slightly higher 43 grams – in comparison, gas power and coal power generate 486 and 1,001 grams on average, respectively. Of the non-renewable sources, only nuclear energy has a footprint comparable to solar or wind¹.

NREL also counted emissions associated with the batteries that might support the grid when solar panels and wind turbines are not operating. Their numbers are also relatively low next to fossil fuels – a lithium-ion battery system was responsible for 33 grams of CO₂ equivalent for every kilowatt-hour of electricity it delivered to the grid¹.

These numbers are world averages – wind turbines and solar panels will naturally be more emissions-intensive if they’re manufactured in a location with a fossil-fuel-dependent energy grid (see Figure 2). In 2020, the United Nations Economic Commission for Europe (UNECE) estimated lifecycle emissions from different electrical sources in different regions. Solar cells ranged from 7 to 83 grams of CO₂ equivalent per kilowatt-hour, depending on region and chemical composition; wind turbines ranged from 7.8 to 23 grams, with offshore turbines tending toward the higher end. In comparison, gas ranged from 403 to 513 grams and coal from 753 to 1,905 grams. Again, only nuclear energy compared to solar or wind as a non-renewable source².

So, we’ve shown that even the very highest-end emissions for solar and wind still do not match the very lowest-end emissions from natural gas, let alone those from higher-emission fossil fuels like fuel oil and coal^1,2. If we examine a high-emissions environment like China, then another life cycle analysis study tells us that onshore wind turbines are, on average, 98% less emissions-intensive than traditional fossil fuels³.

Wind turbines and solar panels quickly make up for their higher construction emissions

If that’s the case, then why do wind turbines and solar panels often attract criticism for their emissions? One possible reason is that, while their total footprint is significantly smaller than those of fossil fuel sources for the same amount of energy, they have larger initial footprints when they’re first plugged into the grid.

Let’s understand what that means. Researchers often divide the lifecycle emissions of a power source into four parts (Figure 3):

• Upstream: Emissions incurred before a power plant starts operating. These are associated with building and commissioning a power source, from extracting raw materials, to manufacturing parts, to transporting them to the site, to building them into a functional wind turbine, solar panel, or power plant.
• Operation (combustion): Emissions that occur while a power plant is operating and which are necessary for the power plant to generate electricity. Fossil-fuel-dependent power plants must generate emissions – not just from burning coal or gas, but from extracting fuel and transporting it to the plant. Solar panels and wind turbines, on the other hand, don’t create these emissions.
• Operation (non-combustion): These might include emissions related to maintaining and operating the power plant (such as transporting its staff to and from the site).
• Downstream: Emissions that occur after a power plant stops operating. These are created while decommissioning, dismantling, and disposing of energy infrastructure.

NREL’s figures (Figure 3) indicate that solar panels and wind turbines do have higher upstream emissions per kilowatt-hour than their fossil fuel counterparts: about 2 to 35 times greater. These include emissions from extracting raw materials, transporting them into a manufacturing facility, assembling them into usable components, transporting them to the site, then installing them as finished solar panels or wind turbines¹.

But it’s crucial to remember that these upstream emissions are only one part of the larger picture. In the case of solar and wind, they are the biggest part. The UNECE says: “Most of renewable technologies’ GHG [greenhouse gas] emissions are embodied in infrastructure (up to 99% for photovoltaics)”². In the cases of coal and gas power plants, however, these upstream emissions are utterly dwarfed by the emissions from burning fossil fuels during operation, which can be 200 to 500 times greater (Figure 3). 

So, even if a solar panel or a wind turbine starts its life with a larger footprint than a fossil fuel source, the renewable source’s lack of combustion emissions from burning fossil fuels means that – if it replaces a fossil fuel source on its power grid – it will make up the difference after a relatively short period of time. This is known as the renewable source’s ‘greenhouse gas payback time’. In fact, analysts often calculate payback time to better inform planning decisions – you might want to place solar panels and wind turbines where they’ll be more effective and have shorter payback times.

An analysis of wind turbines in northwest Europe between 1979 and 2013 had greenhouse gas payback times of 5.3 months on average⁵. In other words, if a wind turbine replaced an equivalent amount of fossil fuel energy on the grid, the turbine would need to generate electricity for 5.3 months to make up for the emissions accrued during its production. Given that wind turbines installed in northwest Europe during that era tended to have lifetimes of 20 to 25 years, we can say that most turbines there have reduced emissions for the vast majority of their respective lifetimes. Other studies generally indicate that wind turbines around the world have payback times ranging from a few months to a year^6,7.

Solar panels similarly tend to have very short greenhouse gas payback times. A 2022 report from the International Energy Agency (IEA) evaluated payback times by country, assuming that the solar panel was assembled in said country and installed on its grid. In no country was the payback time longer than a year. The IEA report says:

“In most countries, domestically-produced solar PV modules (including polysilicon, ingots, wafers, cells and module assembly) need to operate only three to five months to make up for all their manufacturing-related emissions. This measurement is only indicative, however, as a comprehensive lifecycle assessment should also consider all upstream and downstream emissions, including from balance-of-system component manufacturing and PV power plant construction. Nevertheless, although the payback period could double or triple when lifecycle emissions are taken into account (depending on the type of system), it would still be very short considering a PV system’s typical lifetime of 25-30 years.”

(Note that greenhouse gas payback time is different from another commonly cited figure, ‘energy payback time’ – the latter is the time an electrical source takes to make up for the energy used to build it, while the former is the time it takes to make up for the greenhouse gas emissions.)

Of course, greenhouse gas payback times do vary depending on factors like where a wind turbine is manufactured and where it is deployed. If a solar panel, say, is manufactured in a greenhouse-gas-intensive country, it will have a longer payback time. If it is installed in a lower-emissions electrical grid, it will also have a longer payback time, as it has lower emissions to displace.

In most circumstances today, however, solar and wind tend to have relatively short payback times. A 2024 NREL technical report estimated the greenhouse gas payback times of manufacturing solar panels in different world locations and installing them in different U.S. locations. Only in an extreme case of manufacturing a panel in a high-carbon part of Asia and installing it in a low-sunlight region (Washington state) did the panel’s payback time exceed around 5 years – less than a third of the solar panel’s expected lifetime.

Renewable energy has become more efficient

It’s also worth noting that some renewable energy payback times have decreased in the past several decades. Wind turbines and solar panels have become less carbon-intensive to manufacture; at the same time, they’ve also become more efficient. Solar panels, for example, became 45% less emissions-intensive to manufacture between 2012 and 2022, according to the IEA.

This means that payback time figures from the past may not reflect present-day reality. For example, this 2004 NREL report states that rooftop solar panels have greenhouse gas payback times of “1 to 4 years”, several times longer than today’s estimates. It’s misleading to rely on older estimates of payback times or emissions to represent the present or to make predictions about the future.

Furthermore, as wind turbines and solar panels are added to an electrical grid, it will become less carbon-intensive. This could reduce both emissions footprints and payback times of additional wind turbines and solar panels made with that same grid’s electricity.

In fact, UNECE estimated what the improvements would look like (Figure 4). According to their estimates, the lifecycle greenhouse gas emissions of wind turbines would drop between 10% and 13% on average between 2020 and 2050, and the lifecycle greenhouse gas emissions from solar panels would drop between 13% and 18% on average in the same time period (depending on the solar panel’s chemistry)². 

Meanwhile, UNECE estimates that coal and gas plants will see no comparable decline – at most, 3%. The fact that fossil fuel plants emit considerable emissions during operation makes those emissions very difficult to reduce².

Conclusion

As demonstrated above, scientific evidence leaves no doubt that solar panels and wind turbines are far less emissions-intensive than their fossil fuel counterparts. Even the highest-end estimates for emissions from solar panels and wind turbines are lower than the lowest-end estimates of emissions from fossil fuel power plants like coal and gas. 

Renewable sources do have higher upstream emissions than fossil fuel sources, but to cherry-pick these emissions for comparison is misleading. Upstream emissions make up the vast majority of a solar panel or wind turbine’s lifecycle emissions, but are only a very small part of a fossil fuel source’s emissions – the vast majority are emitted from burning fossil fuels as the power plant operates.

In fact, we know fairly well how effective a solar panel or wind turbine will be at reducing emissions, because we can calculate a power source’s greenhouse gas payback time. Solar panels and wind turbines both usually make up their upstream emissions within the first few years, if not the first few months, of their decades-long average lifetimes.

REFERENCES

1. National Renewable Energy Laboratory. (2021) Life Cycle Greenhouse Gas Emissions from Electricity Generation: Update.
2. United Nations Economic Commission for Europe. (2021)  Life Cycle Assessment of Electricity Generation Options.
3. Xu et al. (2022) A comprehensive estimate of life cycle greenhouse gas emissions from onshore wind energy in China. Journal of Cleaner Production.
4. Sharif et al. (2021) Disaggregated renewable energy sources in mitigating CO2 emissions: new evidence from the USA using quantile regressions. Environmental Science and Pollution Research.
5. Dammeier et al. (2019) Space, Time, and Size Dependencies of Greenhouse Gas Payback Times of Wind Turbines in Northwestern Europe. Environmental Science & Technology.
6. Nasser et al. (2024) Carbon footprint and energy life cycle assessment of wind energy industry in Libya. Energy Conservation and Management.
7. Fonseca and Carvalho. (2022) Greenhouse gas and energy payback times for a wind turbine installed in the Brazilian Northeast. Frontiers in Sustainability.
8. Dammeier et al. (2022) Variability in greenhouse gas footprints of the global wind farm fleet. Journal of Industrial Ecology.