Days of Storage Help
The larger your battery bank, the more power you have available for days without sunshine. This varies throughout the country and normally you need more storage in the winter when days are shorter. The days of storage can be as small as 3 days in areas of good winter sunshine and up to 10 days or more in harsher climates. A rule of thumb in using this program is to use the number 9 minus the number that you get from the map location. Example if the location number is 4 then you should have at least 5 days of storage. If the location number is 2 then you should have at least 7 days of storage. Batteries will normally last longer with larger battery banks since they will be deep discharged less. If the storage is absolutely critical, as in mountain top communication equipment, you should consult with a qualified designer. For systems that will be tied to the utility grid you should choose "0" and pick a 4000 watt inverter. This inverter is the only one listed that has pure enough power to feed back to the utility grid. If you use this inverter your system voltage should be 24 or 48 volts since larger inverters are not available in 12 volt systems.