After the process of determining your home energy needs and hopefully lowering those needs by employing energy efficient measures, the next task is to determine the size of the solar power system. The first question to answer is what percentage of your power do you want your solar power system to supply. Some of this decision depends on how much you have to spend on your system. A typical estimate of a direct intertie system without battery backup (>90% of systems are in this category) completely installed is roughly $2000 for every kWh per day that you plan to generate with solar power. Note that this is the cost estimate before incentives are applied. The incentives for installing a home solar power system vary with the size of the system and where you are located. A list of incentives for your area can be found at www.dsireusa.org .
In summary, in order to size your system, you need to have estimates for the following :
- The amount of energy you need.
- The percentage of energy you want to generate with solar power.
- How much you are willing to spend on the solar power system.
Example:
Assume that you have determined that your energy needs are 6000 kWh of electricity per year and you want to supply 75% of this with solar power. The amount of electricity you want to generate per year is 4500 kWh which then averages out to about 12.3 kWh per day. That translates to a price of installation of just over $24,600. Remember, this is the estimated cost before incentives are applied!