Battery capacity explained

Battery size or capacity is measured in kWh (kilowatt-hours). This is the total amount of energy a battery can store. However, the usable capacity may differ from the total battery capacity. Generally, the usable capacity is limited to 80 to 90% of the total battery capacity to increase the lifespan and avoid a potential battery shutdown at very low charge levels. For example, a lithium battery with a 10kWh total capacity may have its usable capacity limited to 80% to increase its lifespan. Therefore, 8kWh of energy can be discharged daily. However, the remaining 10 to 20% is often available in emergencies, such as a prolonged blackout, depending on how the system is programmed.

The solar and battery calculator will help you determine the correct size solar and battery for your home.

What size battery do I need?

Unfortunately, the one-size-fits-all approach is often taken when it comes to sizing a battery, which can lead to poor performance and not meeting the consumer’s expectations. This is typically due to two main reasons: Undersized batteries - do not have enough capacity to meet household demand. Oversized batteries - the solar array doesn’t have sufficient power to charge the battery, typically during the winter months.

To avoid these issues, a battery should be selected and sized according to several important factors, including solar array size (existing or new), system type (on-grid or off-grid), backup power requirements, and most importantly, the evening or overnight energy consumption (kWh). You can use our free solar and battery sizing tool to help determine the correct size battery for your needs. Fortunately, most modern battery systems are modular and scalable so that they can be sized accordingly. With this in mind, we selected the best batteries according to the six following categories:

7 Best Solar Battery Storage Systems

Solar battery storage systems are ways to store energy for nighttime, cloudy days, or power outages. It is important to choose the best battery system for your home, and here are a few of our top picks.

First, Do You Need A Solar Battery Storage System?

If you have solar panels, solar battery systems are not necessary, but they can be beneficial depending on your circumstances.

• If you experience prolonged or frequent power outages. Having a backup battery storage system is very beneficial in this scenario, especially if you have essential systems such as medical equipment. This will ensure that you have power, even when the electricity goes out.
• If you live off-grid. If you live in a remote area or do not use the central utility grid, you will need a solar battery storage system if you want to use electricity at night or when there is no sun to generate power.
• If your area has a Time of Use rate. In some places, the rate of electricity fluctuates depending on the time of day and the rate of demand. It can save you quite a bit of money on your electricity bill to use a home battery storage system if this is the case in your area.
• If you want more sustainable energy. Rather than switching to the grid at certain times of the day, using sustainable energy through battery backup power gives you more sustainability and the use of renewable energy.
• If your net metering policy is unfavorable. In many states, utility companies are working to remove or replace net metering. Having a backup battery bank may be the way to go if you are in one of those states and use solar energy.
• If you want to be energy independent. Even if you live in a brand new HOA neighborhood, you don't have to pay a dime to your local utility company. With the right size solar energy system and battery storage, you can generate and store enough electricity to become totally energy independent.

A solar battery will allow you to use stored electricity at night.

How Much Do Solar Batteries Cost?

The average cost of solar batteries is between $8,500 and $10,000 not including installation. After installation costs are added, the cost of your battery backup system can be between $10,000 and $20,000.

Some factors that will affect the cost are battery chemistry (lithium-ion battery, lead-acid battery, etc), battery capacity, whether or not there is an inverter, battery size, and battery quality. The installation costs will also vary depending on local labor costs and the complexity of installation.

The Best Solar Battery Storage Systems

Best Overall Solar Battery: Generac PWRcell Revolutionary Battery Storage System

This solar storage system goes above and beyond and is not only a powerful battery, but offers up to 9kW (kilowatt-hours) of storage capacity. It offers a standard Outdoor Rated (OR) battery cabinet and is compatible with almost any solar installation and can withstand more extreme temperatures.

Best AC-Coupled Battery System: Tesla Powerwall

The Powerwall is an integrated backup system that reduces your reliance on the grid and stores energy for backup when there are outages. It will give your household continuous power and keep everything in your house running seamlessly.

Best Off-Grid System: SUNGOLDPOWER 12000W Complete Off-Grid Solar Kit

This lithium battery kit includes everything you need for being off the grid. It is complete with a solar charger controller, a monocrystalline solar panel system, an inverter, a battery with Bluetooth, and everything you’ll need for installation and to support your energy needs.

Best Solar Lithium-Ion Batteries: Enphase Encharge 10 Lithium Iron Phosphate Battery

This battery provides low energy costs and features 12 embedded grid-forming microinverter that provide flexibility in your battery capacity. It is reliable, smart, simple, and safe.

Best Indoor Battery Solution: Sonnen Core+

This stackable indoor solution offers up to 60 kWh battery power. It comes with a 10-year warranty and its sleek design is coupled with intelligent energy management, making it safe, long-lasting, and efficient.

Best Lithium-Ion Solar Battery Backup: LG Chem RESU

This DC-coupled solar energy storage system is of excellent quality and offers everything you need to pair with your existing solar system including backup protection against power outages, time-of-use load shifting, storage of excess energy for later use, and greater energy independence.

Best Hybrid Solar Power System: Sol-Ark 4.8kW Universal On-Grid & Off-Grid Solar Kit

This all-in-one hybrid solar system takes gives homeowners a whole new level of storage solutions. It can be installed with a fully powered backup system for energy usage in the case of outages, or it can be fully independent to deliver power to remote, off-grid areas, no matter the amount of energy your household uses.