Home Energy Focus

Archive for the ‘Uncategorized’ Category

More often today, people are talking about living “off the grid”.  While true “off-grid” living entails much more than just generating your own power, this is where we’ll start.  When you first look at living off the grid, you think about freeing yourself from the monthly cost of a power bill.  But think about how much power you actually use on a daily basis.

The typical North American home uses 920 kWh per month (according to the US Department of Energy).  Typical months have 720 hours, which means that on average the typical North American home is using 1.28 kW (1280-Watts) of electricity.  Obviously more power is used during the day, and less at night, but it is important to note that these are averages.  Peak loads will vary widely.  Appliances like refrigerators may use relatively small amounts of power (200-Watts) while running, but can require a massive 1200 Watts during startup.  These momentary spikes are enough to trip circuit breakers in smaller off grid systems.

The types of loads must be accounted for when you’re looking at putting together your solar or wind powered system.  Having enough power to accommodate the startup loads of appliances like refrigerators, microwaves, washing machines and dryers will greatly affect your decisions during system design.  If, for example, you switch to a gas dryer and gas stove, your system can be smaller because it wouldn’t need to deal with these large continuous loads, however you’ve just moved electricity use to gas use.

The larger your system, the more generation capacity and storage capacity you need.  This typically means more solar panels, more wind turbines and more batteries.  Knowing that you can’t get solar power during the night, and the wind won’t blow all the time (or occasionally may be too strong for your turbines), storage is a necessary part of your off-grid system.  Knowing how much power you use and what the peak demands of your appliances are will help you size your system.  Using a P3 International P4460 Kill A Watt EZ Electricity Usage Monitor or a similar tool will help you determine exactly how much power you need.

From there you can size your battery bank, power inverter and charge controller and finally the generation system.  Details on sizing each of these components will follow in future blog articles.