How to do a home energy audit

Electrical Energy: What it is and how to measure it Rod Hinman Energy Efficiency Workshops, Spring 2009

Electricity 101
Volts – pressure pushing the electrons
Amps (current) – flow of electrons
Watts = Volts * Amps

Electric Power: Watts
“Power”, or how fast we are using energy
Watts = Volts * Amps
Also kilowatts (1 kW = 1000 W)

AC / DC
DC = “direct current”
Examples:
12V car battery
35V solar panel
AC = “alternating current”
Example:
120V wall voltage

Electricity 102
Energy – how we measure “useful work” that accomplishes a task
Wash clothes
Light the room during dinner
Heat your tea
Phone your mother
Energy = (how fast using energy) * (how long)
Energy = Watts * Time

Energy: Units
Watt-hour (Wh)
Kilowatt-hour (kWh)
1 kWh = 1000 Wh = 10W * 100 hours = 100W * 10 hours
* remember

Why Measure or Audit?
control

Measure your total use
Read your meter
Use special tools for real-time display
Break consumption down by appliance
Measurements
Estimates

Using HELCO Meter to Calculate Power
Kh is a value printed on meter label: 3.6, 7.2, 14.4
Multiplier is printed on meter label, or = 1 if omitted
Revolutions: number of revolutions of the wheel
Seconds: # seconds that those revolutions took
Example: 3.6 · 7.2 · 1 · (1 rev) /(10 sec) = 2.6 kW Power (kW) = 3.6 · Kh · multiplier · revolutions / seconds

Tools – Whole House
Power Cost Monitor from Blue Line Innovations
Reads dial or flashing light on HELCO meter
Indoor real-time display encourages conservation
Safe install
But finicky setup

Tools – Whole House
The Energy Detective (TED) from Energy, Inc.
Sensor unit in breaker box, electrician needed
Indoor real-time display encourages conservation
Accurate, even at low power usage
Updates every second, both kW power and total kWh energy used
Can connect a PC to log power draw over time

Individual Appliances with Whole-House Tools
Turn off as many appliances as you can
Unplug them or use breakers
Especially devices that cycle: refrigerator, water heater, air conditioning
Measure base power consumption in kW – clocks in your stove, etc.
Turn on an appliance and measure total power consumption in kW
Appliance power kW = total – base
Turn off appliance and repeat with another one

Tools – Individual Appliances
Kill-A-Watt
Watts Up
Plug into wall, then plug appliance into device.

Estimating Appliance Consumption
Look on label for Watt or Amp rating
Usually means peak:
Turned fully on
Under all operating conditions

Estimating Appliance Consumption
Printed Publications
HELCO
Energy Star
Online energy calculators
Home Energy Saver from Lawrence Berkeley National Labs (hes.lbl.gov)
US DoE Office of Energy Efficiency and Renewable Energy (www1.eere.energy.gov/calculators/homes.html)
Others

Example * $0.34/kWh was the effective residential rate for my bill spanning most of September and a couple of days in October 60 60 1000 8.3 label Coffee maker TED measurement HELCO pamphlet HELCO pamphlet “ Kill-A-Watt” measurement HELCO pamphlet Data Source 496.9 = $170 at $0.34/kWh Total 1.3 90 14 CFL 11.8 540 22 32” LCD HDTV “off” 43.2 180 240 32” LCD HDTV on 120.6 Refrigerator 260.0 4500 Hot Water Heater kWh/mo. = W*H/1000 Hours in use/mo. Watts = V*A (usually 120V) Amps Appliance

Other Examples
Room Air Conditioner 500-1000W
Desktop Computer 60-400W
Laptop Computer 10-30W
Toaster Oven 1600W
Incandescent Lamp 60-100W
Pool pump 1000W

Photo Credits
Water pressure by “pbo31”, Bubbling water by “just having some fun” on Flikr
Fire hose by dmuth on Flikr, Faucet: City of Grapevine, Texas
CFL by Outsanity Photos on Flikr
Green clock by Catherine on Flikr
Product photos from company web sites
Others by Guy Toyama and Rod Hinman

Ways to Reduce Consumption
Solar hot water heater: simple payback within 18 months after tax incentives
Set A/C warmer; service the A/C unit
Replace incandescent (halogen, too) with fluorescent lights
Turn off/hibernate computer when not using
Configure monitor to turn off, rather than use screen saver
Turn off printer, especially laser printers

AC Power Watts = Volts * Amps Note: power is not constant, but is always one direction

Units comparison =kiloWatt · Hour = 100 kWh * Hour * 100 hours kiloWatts 1 kW Electricity = Miles = 600 miles * Hour * 10 hours Miles Hour 60 mph Distance Quantity * Time Rate Measurement

Reading Your Meter
Read left to right
Dials spin opposite directions (driven by gears)
If hand between two numbers, pick lower
If hand on a number, pick it if the next hand has passed zero, otherwise pick one less.
Example from HECO site: 13924 kWh

Reading Your Meter: Digital with Net Energy Metering
Screen 3: consumption
Screen 6: production (when meter spinning backwards)
Screen 7: net kWh with initial value set to 50,000
= 50000 + (screen 3) – (screen 6) {note rounding error}

Auditing
Break down your usage by appliance
Measure or estimate how much energy used
Start with largest users

Automotive Mileage Meter
ScanGaugeII
Displays instantaneous and trip MPG
Plugs in under dashboard
Also records other operating parameters

How to do a home energy audit

by Friends of NELHA on Oct 27, 2009

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How to do a home energy audit — Presentation Transcript