Solar batteries explained.

Unsure if you should get a battery with your new system or not? Let's break down how a solar battery works and if it’s beneficial for your home or not. Last week, we explained how a solar panel creates energy and the other parts of a solar system work together to deliver that power to your home. If you missed last week's post, you can check it out here!

‍

To understand solar batteries, you first need to understand that there are two types of energy running through a solar system; 

1. DC (direct-current) - DC energy only flows in one direction. This is the type of electrical current generated by the solar panels on your roof and stored by a solar battery. 
2. AC (alternating-current) - AC energy can flow in both directions. This is the type of electrical current used on the grid and by most things in your home.

‍

Because most of the devices and appliances in your home use AC energy, the DV energy created by your panels must be converted before entering your home. This is accomplished with an inverter. The way that batteries and inverters work together can look different ways. The two most common ways are DC coupled systems and AC coupled systems.

‍

Let’s take a look at the pros and cons of each system type: 

‍

DC-Coupled Systems

A DC-coupled system connects you to the grid in the same place it connects to your solar panels. This requires a hybrid inverter so that it can supply both your battery- which stores DC energy- and the grid- which transports AC energy- at the same time.

‍

Pros:

1. Less energy is lost because your power is only converted from AC to DC once
2. If your DC-coupled system is below 10kW and produces excess energy, it may be eligible for credits with Net Energy Metering (NEM)
3. It requires fewer parts and can potentially cost less

‍

Cons:

‍

1. If you already have a PV system in place, it is more expensive to install a DC-coupled battery system as opposed to an AC-coupled system. 

‍

AC-Coupled Systems

An AC-coupled system uses two inverters, one that charges your solar batter and one that converts energy for your home and the grid.

‍

Pros:

1. More flexibility — since AC-coupled systems require two or more inverters, you can adjust the location of your batteries and other equipment
2. Works with all kinds of inverters
3. It’s a more cost-effective option if you already have a PV system

‍

Cons:

1. Slightly lower efficiency to charge your solar battery due to multiple conversions
2. More equipment means potential for more points of failure and replacement parts needed

‍

Besides having different amounts of inverters, and conversions, what’s the difference between the two kinds of battery systems? Here is a step-by-step breakdown of what happens with a DC-coupled system:

‍

1. Sunlight hits the solar panels and the energy is converted to DC electricity.
2. The electricity enters the battery and is stored as DC electricity.
3. The DC electricity then leaves the battery and enters an inverter to be converted into AC electricity the home can use.

‍

The process is slightly different with an AC-coupled system:

‍

1. Sunlight hits the solar panels and the energy is converted to DC electricity.
2. The electricity enters the inverter to be converted into AC electricity the home can use.
3. Excess electricity then flows through another inverter to change back into DC electricity that can be stored for later.
4. If the house needs to use the energy stored in the battery, that electricity must flow through the inverter again to become AC electricity.

‍

As you can see, including a solar battery in your system- either AC-coupled or DC-coupled- is a great way to become energy independent. However, it can make powering your home with solar more complicated. You have more equipment to worry about and you may lose some energy efficiency. 

‍

When considering adding a battery to your system, first consider if the benefits outweigh the additional cost that a battery brings. For example, do you have access to a NEM program? If so, you may be better off using the credits you generate to power your home when your panels aren’t producing enough, like at night. This is especially true if you have low-producing winter months. Plus, you may miss the opportunity to get paid for the energy you aren’t using. 

‍

There’s so much to consider when deciding whether or not you want a solar battery. Each project brings different challenges and opportunities which is why it’s never a bad idea to talk with one of our experts about your options. Contact us today to get started on an outstanding solar experience.

‍