Determine how much electricity you use. The average house in the U.S. uses 1500 kilowatt-hours (kWh) of electricity per month. Check your electric or utility bill, or log onto your provider's website to see if you can review your household's history of electricity usage over the past year. Include a full year to allow for seasonal changes, and look for peaks: times when your consumption is at its highest, such as mid-summer or during the holidays, to know what your maximum demand for energy could be.
Ascertain how much energy you can generate. The amount of solar energy you can expect to harness varies widely depending on your home's location: its latitude (how close to the equator), climate (how much sun you're exposed to), position (what parts face south) and landscape (whether you have large shade trees blocking sunlight). To get a general idea of the amount of sunlight for your area, check out the resource maps from the National Solar Radiation Data Base (NSRDB). Find out from local meteorologists the average amount of sunlight your area receives throughout the year. Then survey your space, answering questions about location and landscape. Is your house oriented north to south, or east to west? Do you have a back yard or side yard facing south or west? Does the sun rise much higher in the sky during the summer than during the winter? Do you have shade trees blocking sunlight from major portions of your yard or roof?
Determine the type of panels you want to buy. Crystalline panels are the thick rigid panels most commonly seen. The most efficient, mono-crystalline panels, are also the most expensive. Amorphous solar panels made of a thin film are the least efficient but also the least expensive. They can be rigid or flexible and work even in partial shade; the film's flexibility even allows manufactures to produce solar shingles, negating the need for a separate panel to be mounted to the roof or to stand alone in the yard.
Choose which set of trade-offs work best for your budget. Unless you build a cabin in the woods, or resolve to live a self-sustaining lifestyle (go "off the grid" so to speak), you will need to decide how much system you can afford, taking into consideration how much of a payoff you expect and how quickly you expect it. A clean power estimator that accounts for electricity use and home location lets you play "what-if" for various sizes of PV arrays, to help you figure out which investment level fits your budget.
- As long as you reside in an urban or suburban setting, you need a PV system that ties into the current electric grid. Your array offsets the grid so you don't pull all of your power from the electric company, but lets you keep some power flowing in when weather is inclement or in case your system suffers a failure. Two more things to factor into the overall budget: an energy storage system (battery backup) for emergencies such as a power failure, and the cost to insure the panels from damage. Remember, you are adding on to the house structure, so check to see how this affects your homeowner's policy.