In determining the system and approach to increasing your use of renewable energy, we must determine the size of the load that we are supplying with power as well as evaluate the various stratigies for supplying power to that load. This section discusses how to determine the size or your load (sometimes known as draw). The unit of measure for sizing is either watt-hours or amp-hours. We normally use watt-hours because it applies to both AC and DC circuits.
The procedure is the same for all systems, regardless of whether the load is a telecommunications repeater or a house. What we need to end up with is a figure of the average daily watthours consumed. This will allow us to determine how many modules or turbines will be needed to produce the power and how many batteries will be needed to store the power. Even if your aren't planning to store your power, as in most Grid Intertie situations, this procedure will still help you determine how much of your grid usage you're offsetting with renewable energy.
This table is an analysis of energy usage for a representative small home. We have itemized each appliance and its individual run time per day and per week. We then summed the watt hours of all the individual units for a total daily watt hour figure. Making up a chart such as this will allow you to understand where your power is going and may give you ideas for how to reduce your loads in the most effective manner.
Incorrectly assessing loads can end up being frustrating and expensive. Underestimating your loads can lead to major system inadequacies. Overestimating will lead to excess capacity. While many of our hybrid systems have a range of flexibility in providing power, some systems do not. But both problems can be avoided by careful assessment of loads.
Remember: Watts = Volts x Amperes and Watts x Hours of Use = Watt Hours
Other Types of Loads You Need to Take into Account
When you are calculating your building or dwelling's electrical load, it is important not only to account for all your electrical usage, but to determin how you account for that usage.
Ghost Loads are those loads that typically escape analysis unless you're carefull. They tend to fall in to well defined groups that you can look at to determin either how much more energy you have to budget for or how you can modify your energy usage to mitigate their cost.
Heating Loads on the other hand may be loads you wish to exclude from your analysis if, for example, you're planning to power you're loads exclusiivly with a battery bank fed by only by turbines or solar panels. They are those loads that are simply unreasonable to ask certain sources to supply and thus need to supplied from else where (e.g. "the grid", wood stoves, propane or Solar Thermal).
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