Just got myself a P4460 Kill-A-Watt EZ Energy Meter that measures electrical loads from a standard 120 VAC wall outlet. This is a nice device that can help home owners find those pesky inefficient loads, and is a great energy conservation tool. It also allows you to put in a Kwh rate ($0.09/Kwh where we live) and then will calculate your running cost for a specific load on the fly.
This device is also useful for solar system designers. First, it can be used to help homeowners identify inefficient loads so they can take some conservation measures. This is a good step before sizing a solar array, as it can often reduce the total number of panels required. Generally, inefficiencies stem from household appliances like refrigerators and space heaters. Phantom loads also create small but insidious energy “leaks” that can add up over time; common phantom loads are cell phone and laptop chargers.
After taking conservation measures, the designer can use this tool to do a complete load analysis for the household or business. Generally, this approach is uncommon for grid-tied systems, as the local utility will provide average daily consumption information that designers can then plugin into their equations. For off-grid systems, however, this tool can provide an invaluable source of information to help gauge potential load requirements. A small tool like this is probably most useful for the typical homeowner or for the small business, but is less useful in large commercial and heavy industrial environments. And at $23 on Ebay, this isn’t a bad investment at all for the energy-concious homeowner.