Calculate how much Electricity you Use
One of the first steps in buying solar panels is to calculate how much electricity you currently use in your home. This gives you a baseline number for how much electricity you will need your solar panels to generate. This should include all of the appliances that you use, as well as basic home heating or cooling systems that you power with electricity. Typically, your electrical usage changes throughout the year, so you are generally better off if you can simply report how much electricity you've used in the past -- rather than having to estimate how much you'll use in the future.
If you have lived in your house for at least a year
If you have lived in your house for a while, your electric bill will probably include this information. (If this information isn't included on your bill, but you have lived in your house for a while, call the electric company and see if they can tell you over the phone.) Your electricity use is typically stated in KWH, or KiloWatts Hours. For example, your house might use 25 KWH per day, or about 750 KWH per month. Be aware that electricity use is often seasonal -- if you have a central air conditioner, you may use substantially more electricity in the summer than the winter. If you heat your home with electric baseboard heat, you may use substantially more electricity in the winter months.
If you just purchased your house
If you don't have any history with your current house -- perhaps you just purchased it, for example -- your options are a bit more limited. If the house had previous owners and you are on good terms with them, you can ask them to provide you with an old electric bill. However, the amount of electricity that the previous owners used isn't necessarily a good predictor of how much you will use. So, you may want to have a conversation with them where you explain what you're trying to do, and ask them the following sorts of questions:
- How many people (and what ages) lived in the house before?
- How warm (or cool) did they keep the house?
- Did they have any appliances that are no longer in the house that drew substantial power? (Such as an old refrigerator, the 12 computers that they ran in their basement, etc.)
If you aren't on good terms with the previous owners, the electrical utility may be able to tell you the KWH used in the past year over the phone. This will depend on their privacy policies, but many are willing to provide this basic information. Your real estate agent may be able to answer some of the other questions about family size, etc.
If you must estimate...
If this is new construction, you need to estimate your electrical usage. Estimating the actual energy use of all your appliances is basically educated guesswork -- try this page for tips on estimating your appliances' energy usage.
Don't despair if you aren't sure of the exact numbers. Most of the time when people install solar panels in their home they don't expect those panels to provide 100% of their electricity. The most likely scenario is that your panels will provide a bit more (or a bit less) of your household needs than you expected. But those needs change over time anyway -- imagine what is going to happen to your electricity bill when your three toddlers become teenagers!