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How to do a home energy audit


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The Friends of NELHA presented a 3 part workshop called Energy Efficiency and Auditing Workshop in Hawaii. This slideshow presentation by Dr. Roderick Hinman is the first section which discusses what electricity is, how it is measured, and how you can measure the electrical loads of each appliance in your home to make decisions that can save on your home electric bill.

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How to do a home energy audit

  1. 1. Electrical Energy: What it is and how to measure it Rod Hinman Energy Efficiency Workshops, Spring 2009
  2. 2. Electricity 101 <ul><li>Volts – pressure pushing the electrons </li></ul><ul><li>Amps (current) – flow of electrons </li></ul><ul><li>Watts = Volts * Amps </li></ul>
  3. 3. Electric Power: Watts <ul><li>“Power”, or how fast we are using energy </li></ul><ul><li>Watts = Volts * Amps </li></ul><ul><li>Also kilowatts (1 kW = 1000 W) </li></ul>
  4. 4. AC / DC <ul><li>DC = “direct current” </li></ul><ul><li>Examples: </li></ul><ul><ul><li>12V car battery </li></ul></ul><ul><ul><li>35V solar panel </li></ul></ul><ul><li>AC = “alternating current” </li></ul><ul><li>Example: </li></ul><ul><ul><li>120V wall voltage </li></ul></ul>
  5. 5. Electricity 102 <ul><li>Energy – how we measure “useful work” that accomplishes a task </li></ul><ul><ul><li>Wash clothes </li></ul></ul><ul><ul><li>Light the room during dinner </li></ul></ul><ul><ul><li>Heat your tea </li></ul></ul><ul><ul><li>Phone your mother </li></ul></ul><ul><li>Energy = (how fast using energy) * (how long) </li></ul><ul><li>Energy = Watts * Time </li></ul>
  6. 6. Energy: Units <ul><li>Watt-hour (Wh) </li></ul><ul><li>Kilowatt-hour (kWh) </li></ul><ul><li>1 kWh = 1000 Wh = 10W * 100 hours = 100W * 10 hours </li></ul>* remember
  7. 7. Why Measure or Audit? <ul><li>control </li></ul>
  8. 8. <ul><li>Measure your total use </li></ul><ul><ul><li>Read your meter </li></ul></ul><ul><ul><li>Use special tools for real-time display </li></ul></ul><ul><li>Break consumption down by appliance </li></ul><ul><ul><li>Measurements </li></ul></ul><ul><ul><li>Estimates </li></ul></ul>
  9. 9. Using HELCO Meter to Calculate Power <ul><li>Kh is a value printed on meter label: 3.6, 7.2, 14.4 </li></ul><ul><li>Multiplier is printed on meter label, or = 1 if omitted </li></ul><ul><li>Revolutions: number of revolutions of the wheel </li></ul><ul><li>Seconds: # seconds that those revolutions took </li></ul>Example: 3.6 · 7.2 · 1 · (1 rev) /(10 sec) = 2.6 kW Power (kW) = 3.6 · Kh · multiplier · revolutions / seconds
  10. 10. Tools – Whole House <ul><li>Power Cost Monitor from Blue Line Innovations </li></ul><ul><ul><li>Reads dial or flashing light on HELCO meter </li></ul></ul><ul><ul><li>Indoor real-time display encourages conservation </li></ul></ul><ul><ul><li>Safe install </li></ul></ul><ul><ul><li>But finicky setup </li></ul></ul>
  11. 11. Tools – Whole House <ul><li>The Energy Detective (TED) from Energy, Inc. </li></ul><ul><ul><li>Sensor unit in breaker box, electrician needed </li></ul></ul><ul><ul><li>Indoor real-time display encourages conservation </li></ul></ul><ul><ul><li>Accurate, even at low power usage </li></ul></ul><ul><ul><li>Updates every second, both kW power and total kWh energy used </li></ul></ul><ul><ul><li>Can connect a PC to log power draw over time </li></ul></ul>
  12. 12. Individual Appliances with Whole-House Tools <ul><li>Turn off as many appliances as you can </li></ul><ul><ul><li>Unplug them or use breakers </li></ul></ul><ul><ul><li>Especially devices that cycle: refrigerator, water heater, air conditioning </li></ul></ul><ul><li>Measure base power consumption in kW – clocks in your stove, etc. </li></ul><ul><li>Turn on an appliance and measure total power consumption in kW </li></ul><ul><li>Appliance power kW = total – base </li></ul><ul><li>Turn off appliance and repeat with another one </li></ul>
  13. 13. Tools – Individual Appliances <ul><li>Kill-A-Watt </li></ul><ul><li>Watts Up </li></ul><ul><li>Plug into wall, then plug appliance into device. </li></ul>
  14. 14. Estimating Appliance Consumption <ul><li>Look on label for Watt or Amp rating </li></ul><ul><li>Usually means peak: </li></ul><ul><ul><li>Turned fully on </li></ul></ul><ul><ul><li>Under all operating conditions </li></ul></ul>
  15. 15. Estimating Appliance Consumption <ul><li>Printed Publications </li></ul><ul><ul><li>HELCO </li></ul></ul><ul><ul><li>Energy Star </li></ul></ul><ul><li>Online energy calculators </li></ul><ul><ul><li>Home Energy Saver from Lawrence Berkeley National Labs ( </li></ul></ul><ul><ul><li>US DoE Office of Energy Efficiency and Renewable Energy ( </li></ul></ul><ul><ul><li>Others </li></ul></ul>
  16. 16. 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
  17. 17. Other Examples <ul><li>Room Air Conditioner 500-1000W </li></ul><ul><li>Desktop Computer 60-400W </li></ul><ul><li>Laptop Computer 10-30W </li></ul><ul><li>Toaster Oven 1600W </li></ul><ul><li>Incandescent Lamp 60-100W </li></ul><ul><li>Pool pump 1000W </li></ul>
  18. 18. Photo Credits <ul><li>Water pressure by “pbo31”, Bubbling water by “just having some fun” on Flikr </li></ul><ul><li>Fire hose by dmuth on Flikr, Faucet: City of Grapevine, Texas </li></ul><ul><li>CFL by Outsanity Photos on Flikr </li></ul><ul><li>Green clock by Catherine on Flikr </li></ul><ul><li>Product photos from company web sites </li></ul><ul><li>Others by Guy Toyama and Rod Hinman </li></ul>
  19. 19. Ways to Reduce Consumption <ul><li>Solar hot water heater: simple payback within 18 months after tax incentives </li></ul><ul><li>Set A/C warmer; service the A/C unit </li></ul><ul><li>Replace incandescent (halogen, too) with fluorescent lights </li></ul><ul><li>Turn off/hibernate computer when not using </li></ul><ul><li>Configure monitor to turn off, rather than use screen saver </li></ul><ul><li>Turn off printer, especially laser printers </li></ul>
  20. 20. AC Power Watts = Volts * Amps Note: power is not constant, but is always one direction
  21. 21. 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
  22. 22. Reading Your Meter <ul><li>Read left to right </li></ul><ul><li>Dials spin opposite directions (driven by gears) </li></ul><ul><li>If hand between two numbers, pick lower </li></ul><ul><li>If hand on a number, pick it if the next hand has passed zero, otherwise pick one less. </li></ul><ul><li>Example from HECO site: 13924 kWh </li></ul>
  23. 23. Reading Your Meter: Digital with Net Energy Metering <ul><li>Screen 3: consumption </li></ul><ul><li>Screen 6: production (when meter spinning backwards) </li></ul><ul><li>Screen 7: net kWh with initial value set to 50,000 </li></ul><ul><ul><li>= 50000 + (screen 3) – (screen 6) {note rounding error} </li></ul></ul>
  24. 24. Auditing <ul><li>Break down your usage by appliance </li></ul><ul><li>Measure or estimate how much energy used </li></ul><ul><li>Start with largest users </li></ul>
  25. 25. Automotive Mileage Meter <ul><li>ScanGaugeII </li></ul><ul><ul><li>Displays instantaneous and trip MPG </li></ul></ul><ul><ul><li>Plugs in under dashboard </li></ul></ul><ul><ul><li>Also records other operating parameters </li></ul></ul>