Do home solar panels really help fight climate change?

97% of scientists believe that the Earth’s climate is changing and that humans are the reason.

This isn’t new. The fact that carbon dioxide traps heat isn’t in scientific dispute, and the idea that humans burning massive amounts of fossil fuels could affect the climate has been around since at least 1912:

The scientific consensus is equally clear when it comes to renewable energy, including solar. To stop the progress of climate change, the planet must transition away from fossil fuels in favor of zero carbon energy sources, including solar energy. This means that even seemingly small projects like putting a couple dozen solar panels on your home will absolutely help fight climate change.

How much carbon your solar panels offset depends on your local energy sources, which this article will discuss is detail.

The current state of climate science

More recently, scientists looked back at climate models from the 1970s and found that they were remarkably accurate. These models were developed when computers that filled an entire room weren’t as powerful as the smartphone in your pocket.

Since then, 50 years of advancements in computing power, data collection, and scientific knowledge have made climate science only better.

According to the Intergovernmental Panel on Climate Change (IPCC), the planet has fewer than 15 years to achieve net zero carbon emissions. Even if the planet is successful in reaching the goals of the Paris Agreement - and it is currently not on track, partly because the United States is withdrawing from the agreement - the planet will most likely exceed 1.5°C of average warming.

The impacts of climate change in about 150 words

If the global climate warms by 1.5°C, the oceans will rise by 19 inches by the year 2100, causing the displacement of 25 million people globally by 2055 and 60 million by 2095.

132 million more people will experience severe droughts. The average growing season will actually increase by 5 days, but because of drought, crop yields for staples like wheat will drop by 5%.

The global GDP will drop by 8% by 2100, while the economic losses from sea level rise will cost $10 trillion every year.

Diseases like malaria, which already kills close to half a million people every year, will spread further by around 19%.

And this is a best case scenario, assuming that the planet limits warming to 1.5°C - which it currently isn’t on track to do.

Climate change is a massive topic. The IPCC is the global authority, and you can read their extensive reports to get a thorough understanding. Carbon Brief has also put together an excellent interactive that succintly lays out the kind of planetary and human impacts we can expect with 1.5°C and 2°C of warming.

The incredible rise of solar energy

Back in 1979, solar panels used to cost $79 per watt. Today, they’re about $0.37 per watt! The total installed cost, which includes labor, taxes, and supporting equipment is higher: about $3.70 per watt for residential solar, although this varies across the country.

Here’s what that price drop since 2000 looks like:

Because of this rapid drop in price, ordinary homeowners around the world are installing solar panels to save money and help the environment. In the United States, there are over 2,000,000 solar installations across the country. Check out The Solar Nerd map to find out how many of your neighbors have gone solar.

What does this mean for the environment?

Even though solar has been growing really fast in the 21st century, because it started from essentially zero, its still a small percentage of the overall electricity mix.

According to the Energy Information Administration (EIA), solar energy accounts for about 1.5% of total US electricity generation. That doesn’t sound like a lot, but the growth curve and price curves are impressive. There’s every reason to believe that the price of solar and wind energy reached a tipping point in 2019 where its renewable energy is cheaper than coal. If that’s the case, we should expect solar energy growth to accelerate rapidly, in the same way that smartphones took over the world once the technology and price reached a critical point.

How much greenhouse gas emissions do power plants generate?

According to the Enviromental Protection Agency (EPA), electricity generation in the United States accounts for 28% of total greenhouse gas emissions. That’s basically the same as the combined total for cars, trucks, buses, planes, and other forms of transportation.

That’s a huge portion of the total emissions. The good news is that we have all the tools we need right now to reduce our emissions from electricity to zero, and it doesn’t require exotic technology. We have everything we need now with wind, solar, and battery storage.

How much will my solar panels help the environment? Depends where you live.

If you’re thinking of going solar to reduce your carbon footprint, you’ll want to know how electricity is generated in your state. The New York Times put together a nice visualization that shows the percentage of each state’s electricity that is generated by fossil fuels, renewables, and nuclear power.

As you can see, coal just 15 years ago was the dominant fuel source for power plants. Today, it’s been replaced by natural gas and a small but rapidly growing percentage of wind (in blue) and solar (in yellow) power. The amount of renewables varies a lot from state to state, however. Click on the article and you can select your state to see its particular mix.

In some states, like Wyoming, fossil fuels - especially coal - are still dominant. In contrast, Vermont is already significantly zero carbon, with most of its electricity coming from hydropower, and smaller amounts of wind, solar, and biomass.

The chart below shows you how climate-friendly the electricity supply is in each state. The bar shows how much greenhouse gases are released to generate one megawatt-hour of electricity in each state. (Shorter bars are better.)

As you can see, states like Vermont, Washington, and Idaho have significantly lower emissions than coal country states like Kentucky, Wyoming, and Virginia.

Is going solar in my state helpful? A bit about wholesale electricity and electric vehicles.

If you live in a state that already has low carbon emissions, does that mean you shouldn’t bother getting solar panels for environmental reasons? Not necessarily.

First of all, it’s actually quite tricky to determine where your electricity is coming from at any point in time. Electricity doesn’t necessarily stay where its generated, but can be bought and sold on a wholesale market that crossses state and even country boundaries. For example, Vermont imports a significant amount of electricity from the Canadian province of Quebec (which, luckily, also generates most of its electricity from renewable hydropower).

This means that when you flip on a light switch, the electricity could be imported from a different state - maybe one that uses more coal power than your home state. Or, if your state is generating excess power, it could be selling that power to its neighbors. This means that if you have solar panels on your house, your excess electricity could, through the workings of the wholesale market, help make the electricity in a neighboring state a little greener.

Another big issue is that the market for electric vehicles is small but on the verge of an explosion. EVs are expected to make up the majority of vehicles on the road within three decades.

That means less demand for oil, and a lot more future demand for electricity. Solar panels on your house should last for 25 years or more, so if you want to help the grid adapt to the electric vehicle future, adding solar panels will help make that transition easier. It’s even better if you’re powering your own electric car with your own solar panels, because it means that there will basically be zero transmission line losses (compared to an average of 5% losses when sending electricity from distant power plants to homes and business.)

Benefits of distributed solar generation

One criticism levelled against home solar power is that it’s less efficient than utility scale solar plants. Because large solar farms are megawatts or even gigawatts in size, the cost per watt of home solar is quite a bit higher than the cost of massive solar farms that have many thousands of solar panels installed. Does that mean we should stop subsidizing home solar and spend it more efficiently on large solar farms?

Not really. According to California’s electric grid operator, distributed solar and energy efficiency projects have allowed the state to shelve 20 large scale transmission projects and revise 21 more, saving $2.1 billion in total.

This is because when you build a large power plant, you also need to build wires and infrastracture to get that electricity to the places where it’s needed. Not so with rooftop solar, where the electricity gets generated and consumed in the same location, eliminating the need to build more infrastructure.

The result is lower carbon emissions (because 5% of electricity is wasted in transmission) and fewer ecosystem impacts to build transmission towers. Let’s also not forget the wildfires in California, caused by poorly maintained PG&E transmission lines.

Other environmental impacts of solar power

Solar energy attracts a lot of interest from environmentalists, but also a fair bit of criticism and some disinformation from skeptics. We’ve written several articles at The Solar Nerd that address some of these questions and controversies.

• Is net metering unfair to non-solar homeowners? Some utility companies claim that net metering raises the cost of electricity for non-solar households.
• Are solar panels environmentally friendly? There’s a myth that it takes more energy to manufacture solar panels that the panels generate during a lifetime of operation. Here’s the facts.
• Do solar panels contain cadmium or other heavy metals? Some people are concerned about toxic metals inside solar panels, but very few home solar panels uses heavy metals like cadmium.
• Do solar panels cause cancer? One of the more unusual claims is that solar panel generate emissions that can cause cancer. We set the record straight.