You can only store the energy you do not need at the time it was generated. For example; at some point in time, your solar panels generate 6 kilowatts (KW) and you only need 4 KW, the extra 2 KW can be stored. On the other hand, if your solar panels only generated 3 KW (on a cloudy day) and you still needed 4 KW, you would use all of the 3 KW and you would get the other 1 KW from your electric company through your electric meter. In this case, there would be no extra generation to be stored.
Extra energy generate by solar panels can be stored in 2 different ways.
- In batteries.
Batteries can only store a limited amount of electricity based on the size of the battery or total number of batteries you have. When the batteries receive all of the electricity they can hold (they are fully charged), no more electricity can be stored in them. Your batteries will be charged up first before any other extra electricity is sent to the grid.
As a side note, batteries usually are only good for a few hours up to a couple of days and are very expensive at the present time. Also, the electricity stored in your batteries can not be used for your home unless there is no electricity available from your electric company (blackout) .
- On the grid (back to your electric company).
Extra energy that is stored to the grid is available to you automatically whenever the generation from your solar panels do not generate all the energy you need and will be sent to you as you need it. Any stored energy not used this month will be rolled over to next month and will be available to you when you need it. All extra generation stored next month will be added to the rolled over amount. There is no extra charge for your stored energy that is returned to you.
Refer to the answer to the question “What is the grid?” for more information.