The Maine Switch: Be Green Archives
Fred writes a regular column for The Maine Switch's Be Green page.
8 Ways to Save, October 28.
Detailed savings calculations:
- Save $50 by turning off lights and unplugging appliances. One kilowatt hour of electricity costs about 15 cents in Maine. Leave just one 100 watt bulb on overnight (10 hours), or ten 100 watt bulbs on for just one hour, and you've used one kilowatt hour of electricity. $0.15 x 365 days = $54.75.
- Save $60 by keeping your tires properly inflated. According to www.FuelEconomy.gov, you can improve your gas mileage by around 3.3 percent by keeping your tires inflated to the proper pressure. According to the Bureau of Transportation Statistics, the average fuel economy of recent model cars is 22 miles per gallon. According to the Energy Information Administration, the average car is driven more than 12,000 miles per year. Assuming you get average gas mileage without maintaing your tire pressure, 12,000 miles per year / 22 mpg = 545 gallons per year. Assuming you improve your gas milesage 3.3% (to 22.726 mpg), 12,000 miles per year / 22.726 mpg = 528 gallons per year. 545 - 528 = 17 gallons per year. The price of gas over the past year has been between $3 and $4 per gallon. 17 * $3.50 = $59.50.
- Save $75 by air drying your laundry. One load requires 14 MJ of energy. 14 MJ * 0.278 kWh/MJ = 3.892 kWh. One kilowatt hour of electricity costs 15 cents. 3.892 kWh * $0.15 = $0.5838 per load. 5 loads of laundry every two weeks = 130 loads per year. $0.5838 * 130 = $75.894.
- Save $20 by composting kitchen scraps. According to the EPA, people in the United States generate about 8 pounds of garbage per person per day. Of that total, 59.2% (yard trimmings, food scraps and paper) could be composted. 8 * 0.592 = 4.736 of compostable garbage per person per day. 4.736 * 365 = 1,728.64 pounds per year. Assuming a ratio of 15% finished compost to starting garbage, you can make about 250 pounds of compost per year, or 5 5-pound bags. 5 * $4 = $20. Note: if you pay to dump your garbage, your savings will be higher.
- Save $180 by setting back your thermostat. According to Energy Star, homeowners can save about $180 per year by properly setting their programmable thermostats and maintaining those settings.
- Save $100 by washing clothes in cold water. Heating hot water requires about 24 MJ in older washing machines, 12 MJ in new high efficiency machines (because they use half the water). 24 MJ * 0.278 kWh/MJ = 6.672 kWh per load. 6.672 * $0.15 = $1.00. 5 loads of laundry every two weeks = 130 loads per year. 130 * $1.00 = $130. For new high efficiency machines, the cost is $130/2 = $65. Split the difference between savings in old and new machines to get $100.
- Save $50 by installing a low-flow showerhead. Assume you replace a 3.5 gpm 1980s-era efficient showerhead with a modern 1.75 gpm model, you save 3.5 - 1.75 = 1.75 gallons per minute. Assume your shower lasts 7 minutes. 1.75 * 7 = 12.25 gallons of warm water per shower. 12.25 * 365 = 4,471.25 gallons per year. Assume warm water is half hot water and half cold water. 4,471.25 gallons warm water / 2 =~ 2,200 gallons hot water. Assume cold water temperature is 55 degrees Fahrenheit, and hot water temperature is 120 degrees F. Temperature increase = 120 - 55 = 65. Energy required = 2200 gallons * 8.34 pounds per gallon * 65 = 1,192,620 BTUs * 1,055.05585 BTU/joule / 1,000,000 MJ/joule =~ 1250 MJ * 0.278 kWh/MJ =~ 350 kWh. 350 * $0.15 = $52.50
- Save $65 by carpooling, bicycling or walking once a week. Assume a short trip that you skip is 2.5 miles round trip. 2.5 * $0.505 cost to operate a car for one mile = $1.2625 per trip skipped. $1.2625 * 52 = $65.65.
Solar in action, October 2. Related resources:
Invest in your house, September 4. Related resources:
