|My expansion solar panels that cover the extra cost of my 10,000 miles of driving.|
Wednesday, February 25, 2015
Solar panels cut my costs
Before I bought the electric car, the small solar-electric system on my roof would produce about $15 of excess electricity each year. At the rates I pay with my solar panels, that amounts to about 135kwh, or enough electricity to drive over 500 miles. Considering that I have been driving about 10,500 miles a year, that excess amount falls far short of my electric-driving needs. Of course, I knew I would need more solar capacity. So, I arranged to have four more 240-watt panels installed on my roof, with an emphasis on collecting energy from the west. This means the panels will generate the most electricity during the afternoon hours when the summer generation rates are highest. And, I have the flexibility to charge at night when the rates are the lowest, so I can multiply the kilowatts that my system generates to meet my needs.
The new panels on my roof have generated just shy of a megawatt hour (1,000kwh) of power per year. Without the peak-hour generation benefit, that would be enough power to propel my purple car about 4,200 miles. More than 75% of the energy produced by my new system is generated during the peak season, so I get a big benefit from the summer generating schedule. I also charged about 130kwh on the ChargePoint network, which offsets about another 550 miles of driving. This year, I over produced enough electricity to result in a $20 credit due to me (which PG&E drops because there was no over-production of electricity in my case). So, the new solar panels produced enough energy (using time-of-use metering) for me to drive about 10,300 miles.
So, the bottom line is that I spent nothing to drive 10,500 miles. Of course, I had to invest $5,500 in the solar panel upgrade to eliminate my driving costs, otherwise my electric costs would have been closer to $260 for the year. If electric rates remain constant, it would take over 21 years to recover the costs of the solar panels from a strictly financial perspective, but knowing that my car gets much of its energy from solar power provides an intangible benefit akin to the “value” of gambling in Las Vegas. (If energy rates jump by 25% in the next 10 years, I can break even in fewer than 18 years.) Now, if you factor in the savings over gasoline propulsion, the break-even time gets much shorter (to about four years).