1. Energy Consumption:
CO$T

2. kWh Efficiency EnerGuide
OUTCOME QUESTION(S):
S1-3-22:
How can you lower electrical energy use of a household?
Vocabulary and People
kWh Efficiency EnerGuide

3. Purchasing Electrical Energy
Energy companies charge a fee for total energy consumption (usually) per month – “hydro” bill
Total energy is calculated by multiplying power by time used E t
P is the power in kilowatts (kW)
t is the time in hours t E =
P · t P = t
Notice the units:
Time is in hours – seconds are not useful for home billing
Power is in kilowatts – watts are too small to be useful

4. The same energy formula is used but the units must match (kWh)
You make smoothies every day in September
(30 days) using a 900 W blender for 5 min.
How much energy did the blender use that month? E =
P · t
900 W · 1 kW =
1000 W
0.9 kW
5 min · 1 h · 30 (days) =
60 min
2.5 hours
The same energy formula is used but the units must match (kWh) E =
0.9 kW · 2.5 h E =
2.25 kWh

5. “Hydro” charges about $0.08 for every kilowatt-hour (kWh) used
Reading a Hydro Meter
Hydro meter uses 5 dials to measure energy usage:
far right dial is “ones” - far left dial is “ten thousands”
a reading is taken every 1-2 months
Reading
(kWh)
(kWh)
3161 (kWh)
energy used this month
“Hydro” charges about $0.08 for every kilowatt-hour (kWh) used
= $253 this month

6. Sample Hydro bill: kWh used Time rate
This household uses natural gas for heat and has a second bill for the total amount of gas used.

7. It is more efficient if it does the same work with less input energy
Efficiency measures how well a device converts energy into work:
every device wastes some energy
lost as heat, sound, poor insulation…
It is more efficient if it does the same work with less input energy

8. This appliance will use 125 kWh of electricity per month of normal use
EnerGuide labels give consumers an idea of the efficiency of an appliance:
gives energy usage for regular use over time (month/yr)
efficient devices will have a lower energy usage
allows consumer to estimate cost of using the device
This appliance will use 125 kWh of electricity per month of normal use
Energy star: government-regulated symbol used to identify most efficient devices (based on tests).

9. CAN YOU ANSWER THESE QUESTIONS? S1-3-22:
How can you lower electrical energy use of a household?
Vocabulary and People
kWh Efficiency EnerGuide