The Home Automation Forum

Power Consumption in the Home

By James Fillmore

I leave 2 PC's running in my house. One for an HA server the other is my main computer for e-mail and video phone. Both are connected to the Internet via cable modem. We moved into a house about a year ago and our electric bills went from about $100/month at the old house to about $250/month at the new house. I had to do something!

I purchased two current transformers from http://www.crmagnetics.com, model# 4310. They put out 0-5VDC over 0-200A. I have one on each leg of the incoming power and the are wired in series so they ADD and I actually get 0-5VDC for 0-100A. I tied this into an analog I/O module on an industrial PLC and added touch screen operator interface (I used this stuff cause that what I do for a living and am MUCH more familiar with PLC data acquisition than PC stuff).

Anyway to make a long story shorter, we now have a display in the kitchen of the house where everyone can see the power use in amps, watts, kilowatts, kilowatts per hour and most importantly cost of kilowatts per hour. The kids and the wife love it.

Its like a game for the kids to see how low they can keep the power use. They run around the house turning off everything they can to get the power use down!

Power usage I have noticed

Device	Amperage	Comments
Iron	10A	Pulses off and on every minute or so - real easy to see if someone left the iron on.
Microwave	14A	A GE Profile above the stove unit
Washer	12A	A 10 year old Kenmore. This is the single largest power usage in the house cause with 2 kids and a baby we do laundry every day. Multiple loads.
Dryer	7A	Again a 10 year old gas dryer. When both washer and dryer are running it gobbles power.
Fridge	2A	A large built-in GE Profile. I thought this would be worse. Its probably the largest user cause its plugged in all the time but again I would say the washer/dry actually USES more power.

For lights, read on! This was the largest power savings. I have changed many lights to compact fluorescents. What a tremendous savings. We had about twenty fixtures in the downstairs playroom and laundry room that were old, with the ballasts leaking, and they pulled about 30A when all were on.

I replaced all of them with $10 fixtures from Home Depot and used 34W bulbs (actually have only one bulb in each of the 8 fixtures in the playroom area and its plenty bright enough) and now when all are on they pull about 6-7A. Huge difference.

When we first moved in we would leave all these light on round-the-clock. I thought fluorescents were efficient? Not the old stuff I found out. I have to change our two driveway incandescent to CF's this weekend. Noticed they pull a lot of power when they are on most evenings.

Now that we can see what the amp usage is our house uses anywhere from 4 to 7A most of the time. In the evenings with meals, baths, humidifiers, more lighting we run around 10A. Our bills have gone from $250/month to about $80/month this past month. We have actually all tried to keep our daily use to around $2.00/day. This month should be $60 to $70!

Oh and the PC's running without the monitors pull about 1/2A or about 60watts. At $0.1065 per KWH in the Detroit area that's about $5 per month each. I'm actually going to hook up a Toshiba 780 laptop in a 19" rack setup to be my HA server so I should be able to run that for about $2 or $3 per month.

James Fillmore
james267@home.com