How do you determine a house’s hourly electrical demand?

6 Comments

1. BRUZER says:

   June 30, 2009 at 4:08 pm

   You can survey your house and determine the volt-amps (watts) of all the stuff then convert that to kilowatts. Then estimate the time cycles of the frig, the tv computer lights convert that to hours and add it all up. Ex: A 120VAC fridge has a name plate that indicated it pulls 3.7 A. That means 120*3.7 = 444W = .444 kw. If it cycles on and off on average every 15 min (.25 hr) it used .444 kW * .25 hr =111kw-hr. Do that for the TV compoyer lights everything. That will put you in the ball park.

   Or You can buy these nice devices that you plug into and that plugs into the wall and measures the amps and totals the kilowatt-hours for any device. Just plug it in and come back later and see what it reads. Go through that for everything and add it all up.

   But realistically, the best way is to go to your electrical meter every night at the same time and record the kilowatt hours. The meter totals so subtract today’s reading from yesterdays to get what you consumed the past day. Do this for some time and get an average. Your electrical bill will also have all this information as they read the meter too. So read it and check out how it varies with the season.
2. billrussell42 says:

   June 30, 2009 at 4:08 pm

   Look at past bills to get an idea what your average usage is on a monthly basis.

   Add up all the powers for the appliances you have and decide what ones are running at the same time to get an idea of what the max is.

   You still need to be on the grid, for those times when there is no wind. Or you need a very large bank of batteries.

   Best is to arrange with your utility company that you sell them power when wind is good, and buy power from them when wind is low. But some utilities don’t allow that, and some local laws also prohibit it.

   Average utilization factor for a wind turbine is 30%, in a good location. So get one 3x or 4x what your average needs are, and you may break even.

   Also, check with your zoning board, they may have problems with the noise of a turbine. Or you neighbors may.

   email me for any questions.
3. Irv S says:

   June 30, 2009 at 4:08 pm

   You’re going to face two problems,
   and need three answers.
   1. Maximum draw - to size the inverter.
   2. Average wind velocities, (May be seasonal).
   3. Average draw - to size the wind generator & storage capacities.
   Since you want to be ‘off the grid’ you’d best allow a healthy safety factor, as ‘averages’ will be deceiving,
   and you don’t want to be caught short by extreme conditions,
   and storage capacity does degrade over time.
   Since you request calculations for average draw,
   take each load, and assign a ‘diversity factor’
   (Percentage aof time the load runs) as follows:
   Item:…………..Load:…….. Diversity…….Div. Load
   Lighting……. 2400W. … 50% ……. 1200W.
   Well Pump… 3600W. ……10% ………….360W.

   You’d do far better, especially if you contemplate the
   use of wind power to be on the grid, sell back excess
   power, and have the grid as back-up for calms.
   If this is a retirement home, don’t go buying yourself
   an extra headache. You will be less and less eager
   to deal with maintenance etc, as you get on.
4. shijieren says:

   June 30, 2009 at 4:08 pm

   Lots of ways to do this, here is what I would do:

   Jot down the reading on your utility wattmeter the same time each day for a couple of weeks to get an idea of the average power demand this time of year.

   Turn on all the appliances you are likely to be running simultaneously. Read the wattmeter. Wait an hour and read the meter again to get the peak demand.

   Consider that the average or peak demand may be different seasonally. So you might have to turn on the furnace, heat pump, air conditioner to do this test.

   Good luck.
5. D Rock says:

   June 30, 2009 at 4:08 pm

   Check your past bills and you can get your killowatts/per hour.

   Do not take yourself off the grid. If you produce more than you use sometimes the utility will pay for the extra electricty.