How to Choose the Right Solar Battery for Your Home

1. Battery Capacity – How Much Energy Can It Store?

The first and most important factor in selecting a solar battery is capacity, which refers to the amount of energy the battery can store, typically measured in kilowatt-hours (kWh).

Why Does Capacity Matter?

When your solar panels generate electricity, your home either uses it immediately or sends the excess power somewhere. Without a battery, that extra energy goes back to the grid, where you receive a wholesale credit that is far lower than the cost of pulling energy back at night.

With a battery, you can store the excess energy and use it when you need it most, such as in the evening when your panels aren’t producing or during a power outage. But if your battery is too small, it will fill up too quickly, forcing your system to send extra energy to the grid. If it’s too small to last through the night, you’ll end up pulling expensive power from the grid when rates are highest.

What Size Battery Do You Need?

A good rule of thumb is that your battery capacity should be 2 to 3 times the size of your solar system.

For example:

• If your solar system is 8 kW, your battery capacity should be between 16 and 24 kWh.
• If your solar system is 10 kW, you’ll want a battery capacity between 20 and 30 kWh.

This ensures your battery is large enough to store excess power during the day while lasting long enough to power your home overnight.

Other Capacity Considerations

• Scalability: Some battery systems allow you to expand storage by adding additional battery modules. If your energy usage increases over time, having a scalable option is a great way to future-proof your system.
• Depth of Discharge (DoD): Most batteries have a recommended usable capacity, meaning you shouldn’t drain them completely to maximize lifespan. For example, if a battery has an 80% DoD, a 10 kWh battery would provide about 8 kWh of usable energy before needing to recharge.

2. Backup Power – Do You Need It?

The second major factor to consider is whether your battery provides backup power during an outage. Not all solar batteries are designed to keep your home running when the grid goes down, so it’s important to determine if this feature is necessary for you.

Two Types of Battery Modes

1. Backup Mode (Resiliency)

• In this mode, the battery reserves a portion of its stored energy specifically for use during a power outage.
• When the grid goes down, the battery automatically kicks in to power essential loads in your home.
• This is ideal for homes in areas with frequent outages due to storms, wildfires, or unreliable grid infrastructure.
• Some advanced battery systems, like the Tesla Powerwall 3 and Franklin Home Power, can provide whole-home backup, while others focus on critical loads such as refrigerators, medical devices, and Wi-Fi.

2. Self-Consumption Mode (Grid Savings Only)

• In this mode, the battery is not set up for backup but is used strictly to store excess solar energy for nighttime use.
• If the grid goes down, the battery will not power your home.
• This is best for homeowners who rarely experience outages and primarily want to use their stored energy to reduce utility bills.

Do You Need Backup?

• If power outages are frequent, investing in a backup-capable battery is a wise decision.
• If outages are rare, and your primary goal is to lower energy costs, you may not need backup functionality, saving you money on installation and equipment.

Important Note: Backup-enabled batteries often require additional electrical work, such as a backup loads panel, which can increase installation costs.

3. Connection Type – How Will the Battery Integrate with Your Home?

The third factor is how your battery connects to your solar system. There are two main connection types: AC-coupled and DC-coupled.

What’s the Difference?

Which Connection Type Do You Need?

• If you’re adding a battery to an existing solar system, you’ll likely need an AC-coupled battery.
• If you’re installing a brand-new solar system, a DC-coupled battery is often the best choice for maximum efficiency.

Final Thoughts – Making the Right Choice

Choosing the right solar battery comes down to understanding your energy needs, budget, and priorities. To recap:

1. Battery Capacity – Choose a battery that can store enough excess energy to last through the night while preventing energy waste.
2. Backup Power – Decide if you need your battery for power outages or just for lowering your energy bill.
3. Connection Type – Determine whether you need an AC-coupled battery for an existing system or a DC-coupled battery for a new solar installation.

Investing in the right solar battery ensures you get the most out of your solar system, maximize savings, and gain energy independence. If you’re considering adding battery storage, reach out to us at Supreme Solar—we’re happy to help you find the perfect solution for your home!