You’ve invested in a solar system and have decided you want batteries for backup to ensure you always have power for the basics. How do you determine how much backup you need and how long it will last?
There Is No One-Size-Fits-All Answer for This!
Each household has its own rhythm. There is a base level of power that is always cycling to keep refrigerators, HVACs, and other systems on 24/7. Then there is everything else, charging a car, powering a well or pool pump, medical devices, and so on.
The first step in SVE’s analysis process to determine how much battery backup you’ll need, is to calculate your power usage. Ideally you will provide 12-months of actual power bills, or a copy of an online report showing the monthly kWh (kilowatt hours) and how much you spend each month. If you moved in recently, then we’ll look at as many months as you have. The highest and lowest months are considered and then we average the 12-months of usage and cost.
Here’s an Example
Let’s say you have a 12kW system installed with 30kWh of battery backup. Your goal is to offset a large portion of your energy usage and have backup storage that covers the basics for a few days. There is a storm, and the grid goes down. Your solar system will sense that the grid is down and will switch over to batteries until the grid comes back. As soon as there is ample light, the solar system will produce power. It doesn’t have to be sunny to generate power. However, to reach full production capacity it needs to be a sunny, clear day. In Georgia in December, we get about 3 ½ – 4 hours of full sunlight. In June we get 6 – 6 ½ of full sunlight. For this sized system we would not recommend more than 40kWh of backup storage because the system could not fill more batteries than that in December.
The solar system will:
- Produce about 10kW AC each hour on a sunny day.
- Take about 3-hours to fill 30kWh of battery backup.
- Run the basics and refill the batteries at the same time.
How Long Will the Batteries Last?
That depends on which household items you need to keep powered. Of course, you would want enough battery backup to support your basics like fridges, freezers, HVAC, the well pump, lights, and outlets for at least 2-3 days if the grid is down. We can estimate how much power is needed daily once you let us know what needs to be covered.
Once your battery backup system is installed, we suggest you simulate a power outage to learn how the equipment works and to monitor your power usage. That way, you will be comfortable with the system and know how to maximize the batteries when you need them.
Contact SVE
Give SVE a call at 678.833.5191 or email Info@southernviewenergy.com and we’ll work together to explore solar power along with adding battery backup to cover your specific needs.