In some kind of solar photo voltaic system called Off Grid system, your solar system will incorporate batteries that can feed your loads with electricity in case of low sun radiation and night time. But such batteries add a significant cost to your solar system, so it is usually recommended to be used in remote areas in where there is No regular electricity supply exists.
In the past the batteries costs were very high and not much reliable to use for long time span, unit the year of 2015, in where the lithium batteries have been provided to the solar system market, then the prices reduced dramatically, and batteries became more reliable and longer life span. Moreover, the prices will continue to go down, and its anticipated that batteries required for small house solar system come to the solar market with a very reasonable prices, permitting you to use your stored energy in the battery at the night and low sunlight times.
Actually if you live in an urban environment, there are certain conditions in which you can disconnect from the electrical grid, and depend on off grid solar system only as following:
- If you have a large roof space, with no obstacles causing much shadow.
- If you have a high power solar panels with high productivity, that can generate high power per square meter area, like high efficient 400W solar panel power inverter or larger.
- If you have large batteries storage capacity with affordable prices, so you can depend on them at night times with No issues at all. And as said today the solar market became having such great storage capacity and with cheaper prices.
- If you have a reliable "long life span" storage system, so you can depend on for coming years.
- At solar system designing stages you should take care of calculating the proper batteries capacities that can serve our loads for not only one day, but even a week or more because in winter you will get rainy days and less sunlight hours, so affordable long term and reliable storage system that can store excess energy in summer season is highly recommended.