Environmental Science
Calculating a Personal Energy Budget
Introduction:
The Energy Information Administration (EIA), a branch of the U.S. Department of Energy, regularly conducts a Residential Energy Consumption Survey to provide information about household energy use in the U.S. For the most recent survey (2015), data were collected from 5,686 households statistically selected to represent the 118.2 million housing units that are occupied as a primary residence. The survey consisted of household interviews, as well as actual energy consumption obtained from household billing records maintained by the energy suppliers. Statistics on energy use cited throughout this lab were obtained from survey results from the most recent Residential Energy Consumption Survey.
According to the latest survey results, average U.S. energy consumption in homes has decreased by approximately 25% over the past over the past 20 years, with the average household consuming 77 million British thermal units (Btu) per year. This decrease is mainly due to improvements in energy efficiency for lighting, space heating, air conditioning, and major appliances. Newer homes also tend to feature better insulation and other characteristics, such as double-pane windows, that improve energy efficiency and prevent waste.
This lab consists of a survey of energy use in your household. Daily energy use will be calculated for the following categories: electricity and transportation. In addition, you will calculate potential energy savings associated with energy-efficient technologies. Please type all your numbers and answers in RED, so they can easily be found.
Electricity Consumption
Home Light Usage
Artificial lighting consumes approximately 10 -15% of a household’s electricity use (www.eia.gov). The Energy Independence and Security Act of 2007 established new efficiency standards, requiring lightbulbs to use about 25% less energy than traditional incandescents. Energy-efficient lightbulbs typically use about 25%-80% less energy than traditional incandescents, and include halogen incandescents, Compact Fluorescents (CFLs), and Light-emitting diodes (LEDs). The new bulbs provide a wide range of choices in color and brightness, and many of them last much longer than traditional lightbulbs (www.energy.gov). Replacing incandescent lightbulbs with energy efficient bulbs can save a typical household more than $50/year (www.energy.gov).
On an average day at home, record in Table 1 the time in usage and wattage of all lights turned on in the house. If you are using incandescents, the wattage ranges from 40-150 watts and is usually printed on the bulb. For compact fluorescents or LED bulbs, the approximate wattage equivalents are given in this chart:
LED Wattage CFL Wattage Incandescent Wattage
6 – 7W
8 – 12W
40W
7 – 10W
13 – 18W
60W
12 – 13W
18 – 22W
75W
14 – 20W
23 – 30W
100W
25 – 28W
30 – 55W
150W
Calculate kilowatts used in each room and for the whole house using the following formula:
Wattage x hours per day = KWh used
1000
For example, if you have two 40 watt lights in the living room that are on for an hour and 45 minutes:
1.75hrs x 2bulbs x 40watts = 0.14 KWh used in living room
1000
Table 1. Data collected on light usage.
Light Source Used
Wattage
Time in Use
Calculations
Total KWh
Living Room (2)
40
1.75
1.75hrs X 2 bulbs X 40 watts
1000
0.14KWh
Total Lighting
Describe two changes in your lighting usage that would result in the greatest energy savings.
2.How much energy would you save by switching to LED bulbs throughout your house? (from the table, LED bulbs consume energy at about 1/6 (0.17) the rate of incandescents. So, to calculate energy saved by switching from incandescent LED, first multiply total energy used by incandescents X 0.17. That’s the energy consumption with LED bulbs. Subtract that number from the total to find energy savings.
____________KWh saved
Electrical Appliances
Heating and cooling homes consumes the greatest amount of energy, and accounts for almost half of total energy use in U.S. homes (www.eia.gov). Appliances account for the second-largest use of energy and consume 35% of the total energy used in U.S. homes. To calculate annual energy consumption from appliances, you must do the following:
Estimate number of hours per day an appliance runs. For most appliances, you can do this by
recording how much time per day an appliance is used (record in Table 2). For those appliances that
cycle on and off, like a refrigerator, divide the total time the appliance is plugged in by 3.
Find the wattage of the appliance. There are three ways to do this:
– it may be stamped on the appliance (look on bottom or back if possible).
– if amps are provided, multiply that by 120volts to get wattage.
– use an online table to estimate wattage of common appliances, such as
http://www.energy.gov/energysaver/articles/estimating-appliance-and-home-electronic-energy-use
Scroll down the page to find a link to Home Energy Saver which lists wattages.
Table 2. Data on appliance use
Appliance
Wattage
Hours/day
KWh = wattage X hours
1000
Total appliances
Describe three changes in appliance use or heating/cooling that would result in the greatest energy savings in your household.
4How many KWh would these changes save? ______________KWh (You may estimate here. For example, you may decide to lower the thermostat, and you may estimate that this would save 20% of your heat pump cost. You can then subtract this from the total. Or, you may decide to ditch the hot tub, if you have one. You can then subtract this from the total.)
III. Transportation
An average U.S. household travels 20,000 miles per year, and consumes over 1,000 gallons of gasoline per year (U.S. EIA, 2009). With gasoline prices at $2.50 per gallon, that equates to $2,500 spent per year on gasoline.
a. Estimate the miles you travel by car in a typical day. ____________ miles/day
Calculate yearly mileage (answer in 5a x 365days/year) = _________________ miles/year
How many miles/gallon (mpg) does your car get? _______________ miles/gallon
Calculate how many gallons of gas you use per day: 5a = __________ gallons/day
5c
Calculate gallons per year: 5d X 365 days/year = __________ gallons/year
Calculate the number of gallons of gas you would save per year driving a car getting 10 mpg more than your current one.
5b = ______________ gallons/year
5c + 10
5e – 6a = ____________ gallons/year saved
Gas hybrid cars can average 50 mpg. How many gallons of gas would you save per year if you drove such a gas hybrid car?
Gas used with hybrid: 5b = __________gallons/yr used with hybrid
50mpg
5e – 7a = ______________gallons/yr saved with hybrid
Assume gas is $2.50/gallon. What is the cost difference in gas among the three vehicles?
Your Car Car getting 10 mpg more Gas Hybrid
Total gallons consumed per year: ________________ _________________ _______________
Total cost per year: ________________ _________________ _______________
(gallons consumed X $2.50)
Refer back to your estimation of daily mileage (5d), and convert this number to BTU’s using the following equation:
gallons/day x 114,100 BTU/gallon = __________BTU’s/day
Convert this to kilowatts and add to your daily grand total in Part IV.
BTU’s = ___________KWh/day
3412
Total Personal Energy Consumption
Fill in the blanks below with total energy use in KWh per day for each category. Add KWh from each category to get total KWh used per day.
Electricity
Lighting ________ KWh per day
Appliances ________ KWh per day
Transportation ________ KWh per day
Total KWh used per day: _________
How much are you spending on energy use per year? In Maryland, the average cost per kilowatt/hr. is approximately $0.115. (https://www.eia.gov/electricity/state/maryland/)
KWh per day X $.115 = $_________ per day X 365 = $____________ per year
How much energy could you conserve by implementing all your proposed energy-saving techniques?
Savings in electricity
________ KWh per day in lighting savings (from Question #2)
________ KWh per day in appliances savings (from Question #4)
________ Total kWh saved
Savings in gasoline by driving a gas hybrid
________ gallons of gas saved, per day, by driving a hybrid
(5e-7a)/365
How much money could you save yearly by implementing all your proposed energy-saving techniques?
Electricity Cost Savings
Total KWh saved X $0.115 = $________ savings per day
14a X 365 days/year = $__________ electricity savings per year
Transportation Cost Savings
From question 8:
yearly gasoline cost for your car – yearly gasoline cost for a gas hybrid =
$____________
