Climate Protection: Where will we put all the solar panels?

People ask me where we will put all the solar panels when everyone drives an electric car and heats their homes with heat pumps. The curiosity is whether solar panels are going to ruin millions of square miles of farmland, or are they going to be just something that gets installed on top of buildings.

To get a sense of what is needed, here are some back-of-the-napkin calculations about the solar you would need if you lived a typical all-electric life, and some idea about whether you could install it on your home.  

The average person in Snohomish County drives about 7,000 miles each year, and there are about 2.6 people per household. The average household drives about 18,200 miles a year.  

The average electric vehicle gets about 2.8 miles per kilowatt (kWh) hours, which is the amount of electricity you buy from the Snohomish County Public Utility District (PUD). For example, the PUD sells electricity for about 12 cents per kWh. For your driving, you would need about 6,500 kWh each year.

Most people in Washington heat with electricity, and the minority that heats with gas burns about 51 therms of gas each year. About five to 10 of those therms are wasted up the chimney, so the actual number of therms used for heating is about 46 or less.  

A therm has the same energy as 29.3 kWh. For heating, a heat pump generates about 3.5 times as much energy as it draws in electricity. To produce 46 therms of heat, a heat pump would use about 385 kWh.

The average home in Washington uses about 27.7 million BTUs of electricity for all purposes other than home heating (and driving). That’s about 8,100 kWh.  

Altogether, a typical all-electric home in Washington needs about 15,000 kWh of electricity each year.

In Western Washington, a home gets about 1,000 kWh each year for each kilowatt of installed generation capacity. You can buy a solar panel with 0.44 kilowatts of capacity. (Older panels have lower capacity.) That 0.44 kilowatt panel would produce about 440 kWh each year.

You could generate the 15,000 kWh you need with 34 panels. That 0.44 kilowatt panel covers about 20 square feet. You would need panels that cover about 700 square feet of your rooftop, which is completely doable for most single-family homes.

About half our energy will come from wind

Wind farms will generate about as much electricity as solar. Electricity from wind costs about the same as electricity from solar, and wind can generate through the night, reducing our need for batteries. It would work well if the average home in Washington generated half of their electricity with about 17 solar panels and got the rest from wind farms.

Solar farms use 2% as much land as ethanol-corn farms

Not everyone can install solar on their rooftops. Apartment towers like the tall towers in downtown Seattle do not have enough rooftop for the solar their residents need. Another challenge is single-family homes that never get sunlight. For those homes, some of their electricity will come from solar installations on fields.

As long as we’re using fields to generate energy, some folks would rather grow corn to turn into ethanol. If you want to use farmland to create energy to drive cars, you can cover it with corn that is then transformed into ethanol, or you can cover 4% of your corn fields with solar panels to get the same amount of transportation.

An acre of corn field in the Midwest can be turned into about 550 gallons of ethanol. Ethanol has less power than gasoline. Those 550 gallons are the equivalent of 386 gallons of gas. The average U.S. vehicle gets about 25 miles to the gallon, so one acre can drive a car about 10,000 miles each year.

An acre of solar in the Midwest generates about 200,000 kWh per year.  The average EV gets about 2.8 miles per kWh. That means an acre of Midwestern farmland covered in solar panels can power a car about 560,000 miles each year.  

As Bill McKibben has pointed out in Here Comes the Sun, solar panels on 2% of an acre would drive cars as far as a full acre of corn. And solar panels require no fertilizer, pesticides or watering.  

Solar panels increase crop yields

Solar and agriculture are not an either/or deal. You can have both together.  In many places, solar panels increase the productivity of fields. Some solar farms are providing pasture for livestock. Plants need sunshine, but many plants thrive better with less sunshine than is available. 

For example, you have heard of “shade-grown” coffee. Even in the Northwest, many gardeners can tell you about the plants in their gardens that thrive in partial shade. 

In the Midwest, with our current global warming, many corn fields dry out before the corn can be harvested. Some shade could even help even corn in the Midwest.

Growing produce under solar panels that shade the plants for part of the day allows farm workers to stay in the shade as they harvest the crops.  That’s a huge deal as climate change pushes temperatures higher.

Solar panels reduce evaporation

In some places, solar panels are being installed over irrigation canals and reservoirs. Keeping water in the shade reduces how much evaporates, and as droughts worsen with climate change, that’s a big help.

The bottom line: We will put the solar panels on top of our homes, businesses, canals, reservoirs, parking lots, and over our crops and pasture lands. Many farms will install solar panels to improve crop yields and protect workers.