A friend recently forwarded on a good question:
Which creates a more positive environmental impact?
- Adding a 10kW PV system to one’s home?
- Buying an EV in place of a 35mpg gas-powered car?
For extra credit, which offers the most environmental savings per dollar spent?
Fortunately, some data answers this question pretty quickly.
We’ve had solar panels on our house for just about 30 months now. According to our solar monitoring service, the 31,673 kWh we’ve generated from solar are the equivalent of 2,797 gallons of gasoline.
When I was driving my Mercedes, I was consuming about 30 gallons of premium gasoline a month. Over 30 months, that adds up to 900 gallons of gasoline consumed. While an electric vehicle would save that 900 gallons of gasoline with no additional emissions, the solar panel array created more green benefit by a factor of about 3. Yes, a 35 mpg car would burn less fuel than the Mercedes did, but that just makes the electric vehicle savings worse, not better.
Solar panels also produce power in the summer time when the power grid is at peak load. As such, one can argue that their benefit is actually greater than the numbers would suggest because they reduce the need for the power utility to buy high-emissions natural gas or coal-based power to satisfy peak demand. We already had an ultra-low emissions vehicle, so despite the fact that the Mercedes burned gasoline, it was a less harmful polluter than many of the peak demand power plants.
The question of which system generates more environmental savings per dollar is even more clear. Our 9 kW solar array was about $42,000 before the 30% federal tax rebate, which brought its cost down to $29,400. The Tesla was more than double that price and only gets a total of $8,500 in tax rebates (net cost just about $100,000, although one could argue that we could do without about $10K in the fancy extras to achieve a better green quotient).
Bottom line: The solar panels create about 3 times the green benefit of the electric car if we ignore cost. On a per-dollar basis, the benefit of the solar panels is about 10 times that of the electric car. So if you are considering which green project to do first, installing the solar panels first should be your priority (assuming your house is a suitable site for solar; not all houses are).