Planning a Solar System
Planning a Solar System
The first step in planning a solar system is to calculate how much 12-volt DC electricity you use in an average day so you can determine the number of ampere-hours needed in the battery bank. If you plan to operate any 120-volt AC equipment from an inverter, also include this usage. See the table below to determine the average consumption of typical AC and DC equipment.
There is no precise way to determine how much battery capacity you will need, but there is a method you can use: Assuming you follow the conservative practice of discharging the batteries to around 25% of capacity, multiply the total of daily ampere-hour usage by four. The resulting figure will be close to the minimum amount of ampere-hours you'll need.
Using this formula, a daily usage of 30.5 ampere-hours woud require a battery or battery bank with at least a capacity of 100-ampere-hours, such as one Group 27 battery (105-ampere-hours), two Group 24 batteries (150-ampere-hours), or two 6-volt golf-cart batteries. One golf-cart battery provides 220-ampere hours, which is more than you need for the usage in the example, but you must use two 6-volt batteries wired in series for 12-volt output.
Once the battery capacity is figured, you can determine how many panels you will require to achieve the minimum charge. A good way to figure this is to allow one watt of solar power for every two ampere hours of battery capacity or pair a 50-watt panel with a 100-ampere-hour battery.
*Approximate Average Power Consumption of Widely Available 12-Volt DC Appliances | |
Description | Amps |
| Lighting |
|
| Kitchen |
|
| Household |
|
| Tools |
|
| Communications |
|
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