Okay, so this posting has nothing to do with St. Paddy’s day, but hey I had to throw that in there. 
Well, Margaret got a new job a few weeks ago, and though it isn’t really about greening the house specifically, it is related to being green at home in a round-about sort of way.
Why?
Because she got a job working at Sunpower, a leading maker of solar panels! Woo hoo!
Her new job is to sell large installations of solar photovoltaic cells to large retail store customers. I can’t tell you which customers they are until the deals are closed, but these are large box stores you would find at a mall. They have lots of unused roof space where the panels can be colocated.
An interesting new twist on solar panel sales is the new approach that Sunpower and its competitors are now taking. The panels are installed on the roof, but the retail store does not own them. Instead, they simply buy the power they generate. Sunpower sells the panels to a holding company that is created for the deal, which a 3rd party company finances. Typically, the 3rd party is a large investment firm that sees it an an investment opportunity. The holding company will buy the panels, install them on the roof, then sell the power to the retail store in a sort of power purchasing agreement. With the tax incentives provided to companies that invest in solar panels, the holding company can offer the electricity to the retail store at a rate that is competitive with “brown power” (their word for traditional utility-generated power that produces carbon and other wastes).
Filling the roof with panels often provides up to 30% of the energy usage for that retail store during the day. With net metering, electricity is sold back to the utility company during the day when the panels are going strong and there is more than enough electricity to run the store. At night or during the morning or evening when there is not enough light to power the store, the utility provides energy back to the retail store.
This is not a 100% solution, but at least it’s a start and it shows that the retail stores are doing something.
Another idea would be to fit solar panels over parking lots as well. This has two advantages: the extra power of course, and at the same time, customer’s cars are shaded from the heat of the sun. Often, parking lots are larger than the actual roof space of the store itself, so this has the potential to generate even more electricity. However, there is the complication that the parking lot and building are most often not owned by the retail stores, but by some landlord instead, so they would have to be brought in on the deal as well.
In any case, her new job is a 45 minute drive away from our house, which balloons to 1 hour 20 minutes during commute hours. She really wanted a car that has the carpool lane stickers on it so that she did not have to sit in traffic for such a long time. This presented me with a perfect opportunity to advocate buying the Prius that I’ve always wanted.
So we did! We bought a 2-year old pre-owned Prius with all the bells and whistles, and of course, the stickers.
It’s a cool eco-toy for techno-weenies like myself, but also has some real advantages. One tankful of gas is about 8.5 to 9 gallons. At today’s gas rate of $3.68 a gallon at the stations near us, that represents a $31 to $33 or so fill-up. Our other car (a BMW) typically fills up with 16 gallons but gets a similar range. This is saving us $27 a fill-up, once a week, which is about $1400 a year. It would take only 5 years to pay off the added cost of a Prius with stickers over buying another regular-fuel vehicle, and many many more years to actually pay for the vehicle itself over not buying anything. But, we would have needed a new vehicle soon anyways, as both of our other cars are over 110K miles already.
We intended to keep all 3 cars and run them into the ground: the Prius for saving gas and money, the BMW for comfort or when the Prius is already used by the other spouse, and the 4Runner for hauling stuff, towing stuff, or for runs to stores to buy mass quantities of food or supplies.
The carbon savings would look like this. First, let’s calculate how far we drive to work each year.
Margaret: 40 miles each way * 2 trips per day * 264 working days per year = about 21,000 miles per year
Edwin: 23 miles each way * 2 trips per day * 264 working days per year = about 12,000 miles per year
Before we bought the Prius, Margaret drove the BMW to work, and I drove the 4Runner (the longer trip gets the more efficient vehicle) , we would get the following carbon usage (using a figure of 20 pounds of CO2 produced per gallon of gasoline):
BMW: 21,000 miles / 24 mpg = 955 gallons = about 19,100 pounds of CO2
4Runner: 12,000 miles / 16 mpg (!) = 750 gallons = about 15,000 pounds of CO2
Total: 34,100 pounds of CO2
Now, with Margaret driving the Prius the longer distance to work, the BMW is freed up for me to drive to work instead.
Prius: 21,000 / 48 mpg = 438 gallons = about 8750 pounds of CO2
BMW: 12,000 / 22 mpg = 545 gallons = 10,900 pounds of CO2
Total: 19,650 pounds of CO2
Savings: 14,450 pounds of CO2, or about 42%.
Notes:
Yes, the Prius is supposed to get better than 48 mpg, but there are some inaccuracies in the way the EPA measures fuel efficiency. Basically, they don’t run the car on a tank of gas and see how far it goes. Instead, they measure the tail pipe emmissions, which are pretty much zero during the times when the Prius is running on the battery, which skews the results. The EPA (and Toyota of course!) claim 55 mpg. However, the reality is closer to 48 mpg based on how much gas is used to drive the miles we drive.
Note that we saved more fuel, money, and carbon than expected because I could also drive a more fuel efficient vehicle to work as well. (Well, more fuel-efficient than the one I was driving before!)
Anyways, buying the Prius probably didn’t make much economic sense. However, we had to buy a new car sometime soon as the 4Runner has 190K miles on it and is starting to need lots of repairs. Plus, Margaret feels better pulling up to work in the Prius when all the other employees are green activists as well. It will be especially useful when talking to her potential customers, showing that she walks the green walk as well as talking the green talk!
