They Keys To Understanding Batteries

Why We Sometimes Need Batteries

Batteries become necessary when utility companies do not offer a good net metering program. A good net metering program would be defined, in mu opinion, as a buyback rate that is at least 75% of the retail value. Once the buy back value is less than 50% the retail cost, there is not many ways getting around not needing a battery. This is completely dependent on where you are located. In many parts of the country, a 1 to 1 net metering program is still available. Reach out to us to get a detailed proposal taking your utility company's rate schedule into account. 

The other reason a battery storage system would be necessary in addition to your solar system would be if you are wanting to achieve a back up system in the event of a grid black out.

Backup or non-backup?

An important point to make is just because you are having batteries installed, it doesn't automatically mean you will have backup. In order to achieve backup, your system must have some sort of transfer switch which will disconnect you from the grid in the event of a blackout and allows you system to form a micro-grid, being powered by the solar panels and battery storage. This is crucial to know if you are being quoted one of the other because the price difference between the two is generally $4-7,000 depending on several factors. 

When in it comes to designing a solar + battery system versus just a solar system, the key is understanding how much power is going to be consumed by the home directly during the time of production, and how much is produced in excess that needs to be captured and stored by the battery. Depending on someone's usage pattern through each 24 hour day, a household with the same overall usage could need two different sized batteries. Let me explain.  

Let's say we have two homes. Each home uses the same 12,000kWh annually...

Example 1 :

Home number one consists of a young family with a couple of kids under the age of 10. Usually this family wakes up around 5-6am, takes care of morning tasks in the house and uses appliances to cook. Then after they get the kids off to school, they both go to work most days where they will be out of the house the majority of the day. Then in the afternoon/evening time, everybody comes home, homework is being done, dinner is being served, etc.. The energy usage of this house would be a spike in the morning and a spike in the evening with a lull mid day and less usage at night unless they are running an AC all night. This family is going to need a larger battery than in the next example because they are consuming power mostly outside of the peak production hours. 

In this theoretical example,  the system is producing around 33kWh a day total and about 10kWh is actually used in real time from the live production. They would need at least a 23 kWh battery pack to get them through an average day. To truly be fully self sustaining, we would have to use winter month production although this is not how most will design. 

Example 2 :

Home number two consists of a retired couple that spends most days leisurely at home. While they still are out and about, they spend more time at home in the middle of the day and do higher electricity usage tasks, like laundry, in the middle of the day most of the time. 

Of the 33kWh they are using on average per day, 23kWh is used in the middle of the day and is able to be pulled from the solar system in real time, avoiding any need to store in the battery. 

In this case, 10kWh is unable to be consumed during the time of production. This home would essentially need a 10kWh battery set up in order to capture the excess energy. 

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