It is vital to choose the type and number of PV panels appropriate for the amount of energy you wish to produce. Correctly sizing your system is particularly important for off-grid systems not connected to an alternate power source. It is possible to add panels to the system in the future, but there are drawbacks (installation cost). In some cases, it may be cheaper to install extra capacity from the start.
First, decide how much electricity the PV system must produce – all or just part of your household consumption? Check past utility bills to find out how much electricity you use. The size of the PV system depends on:
- the power needed to meet your energy demand
- solar radiation resource: the amount of available sunlight
- the efficiency of the type of PV panels you choose
- available space
- orientation of your panels
PV systems are rated by their power output. According to the U.S. Department of Energy, systems rated between 1 and 5 kilowatts are usually enough to meet the needs of home and small business owners. The table below is a rough guide to sizing your PV system.
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