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Best Batteries for Your Home Solar System

June 17, 2021

A solar battery permits you to regulate your power consumption and where your energy goes. Moreover, it offers you with backup power should an outage happen. Bearing that in mind, different batteries come with various features. The battery that works for your solar power setup and lifestyle depends on several factors. In this blog post, Sun Solar Electric reviews the best solar energy batteries. We proudly offer exceptional installation services to residents of the Bay Area and Northern California.

What are Features of an Effective Battery for Your Home Solar System?

There are specific specifications that a homeowner should put into account when reviewing different solar battery options. They include:

Capacity and Power

The term "capacity'' can be defined as the electricity amount, which a battery stores. It is measured in kilowatt per hour. Many batteries are stackable, and you can use several batteries with a solar-plus-storage system to obtain additional capacity.

Although capacity tells you the size of the battery, it does not show you the electricity your battery can offer. To understand better, you need to put into account the power rating of your battery.

If a battery has a low power rating and high capacity, it will give low electricity for long. In contrast, batteries with higher power ratings and lower capacity can run your home for a couple of hours.

Battery Lifespan

How long will your battery last? For house energy storage, the battery should cycle every day. The ability of the battery to hold charge will progressively reduce the more the battery is used. A solar battery is like your cellphone; you charge the phone every night and use it in the daytime, and as the smartphone gets older, you start noticing that the battery is not keeping as much charge as it did when you first bought it. If, for instance, a battery has a warranty of ten (10) years or five thousand cycles at 70% of the original capacity, your battery will have less than thirty percent of the initial capacity to store charge when the warranty expires.

The battery will have a warranty that guarantees a given number of years or cycles of effectiveness. Since battery performance is reduced with time, many manufacturers will guarantee that your battery keeps specific capacity during the warranty. Therefore, to effectively answer "how long a solar battery will last," it varies with the brand you purchase.

Depth of Discharge

Many solar batteries should retain some charge always because of the chemical composition. In case a homeowner uses one hundred percent of the battery's charge, the battery's lifespan will be substantially reduced.

A battery's DoD means the battery's capacity, which has been used. The manufacturer should indicate the DoD for ideal performance. For instance, if a ten kilowatt per hour battery system has a depth of discharge of ninety percent, you should not use nine kWh of your battery without recharging it. That means, the higher the depth of discharge, the more battery capacity you will use.

Round Trip Efficiency

A solar battery roundtrip battery efficiency means the amount of energy used as the percentage of the amount of energy that your battery took to store. Assuming a homeowner feeds ten kilowatts per hour of electricity into their battery and gets ten kWh of power, the solar battery has eighty percent round trip efficiency. The higher the roundtrip efficiency, the higher the economic value you'll get out the battery.

What are the Best Batteries to Consider in 2020?

Are you considering changing the battery storage bank or installing a solar power system? The section below offers a comprehensive guide with everything you need to purchase a battery that will not disappoint.

Sonnen Battery

Sonnen is one of the biggest names in the energy storage market. A Sonnen battery is an all-in-one solar battery system solution. It provides numerous grid-tied purposes such as managing time-of-use electricity rated for saving on the electricity costs and improving household self-consumption. Additionally, the battery comes with a backup power capability.

Sonnen batteries come in seven various sizes with usable capacities and varying power, namely:

  • Eco 4 with the power of 4.5 kilowatts and user capacity of 4 kilowatts per hour
  • Eco 6 with the power of 4.5 kilowatts and user capacity of 6 kilowatts per hour
  • Eco 8 with the power of 4.5 kilowatts and user capacity of 8 kilowatts per hour
  • Eco 10 with the power of 9 kilowatts and user capacity of 10 kilowatts per hour
  • Eco 12 with the power of 9 kilowatts and user capacity of 12 kilowatts per hour
  • Eco 14 with the power of 9 kilowatts and user capacity of 14 kilowatts per hour
  • Eco 16 with the power of 9 kilowatts and user capacity of 16 kilowatts per hour

The power of a battery determines which appliance you can use with it. On the contrary, usable capacity controls how long the devices could be used. A solar panel battery with high power can power many devices at a go, whereas a battery with high usable capacity could store more energy.


The battery is AC-coupled, and direct current electricity flows from a solar panel to your solar inverter, which converts the electricity to alternating current electricity. Then the AC electricity will go to another inverter, which transforms your power to direct current for storage or flow to home appliances.

Backup Power

This solar battery has backup power abilities. Unlike many solar batteries that need a transfer switch to permit for off-grid operation, Sonnen batteries have an automatic transfer switch. With the excellent power set up, the battery system automatically powers the appliances whenever the grid is down.

Round Trip Efficiency and DoD

All Sonnen battery sizes have a DoD of 100% and roundtrip efficiency of eighty-six percent. In other words, for every ten kWh of power a homeowner puts into their battery, they will get an output of 8.6 kilowatts per hour.


This solar battery is a lithium iron phosphate battery. Lithium iron phosphate batteries are known for their robust safety and power rating.


The battery has a ten thousand cycle or ten-year warranty. The battery also maintains 70% of the capacity to keep charge during the warranty period.


This battery integrates well with the solar panel, particularly if the utility has removed or reduced net metering, or demand charges. It permits a homeowner to maintain a power supply at night or daytime provided they stored power from the solar panel when it is sunny.

  • Size - There is only one size or model of LG Chem RESU available in the US (LG Chem RESU 10H). It has a 5.0 kWh and 9.3 kilowatts per hour of power rating and usable capacity, respectively. The battery system is modular, and you could add other batteries to the storage. It is particularly essential if you need to install several batteries in a house with huge energy demand. However, it is recommended that more than two RESU batteries should not be wired in parallel.
  • Chemistry- LG Chem RESU is a lithium nickel manganese cobalt oxide battery. It is famous for its increased safety and high energy density.
  • Backup power- LG Chem RESU is compatible with many brands and off-grid inverters. In other words, provided you install the right component, the battery can offer backup power when your grid goes down.
  • Performance metrics- The LG Chem RESU battery has a DoD of 95% and a roundtrip efficiency of 94.5 percent.
  • Warranty - The battery comes with a warranty of ten years and a guaranteed warranty capacity of sixty percent as long as the energy is below 22.4 MWh.

Tesla Powerwall

The Tesla Powerwall battery system has made a significant impact on solar and home energy storage technology. Tesla Energy first released its first generation in 2013. It was a high voltage DC-coupled battery with a capacity of 6.4 kilowatts per hour. The second generation comes with an inbuilt charger and doubles the storage capacity.


The solar battery used lithium NMC battery cells.

The second-generation battery is easy to handle, install, and compact. The battery has a power rating of five 5.0 kW and a usable capacity of 13.5 kWh. It has a switch on the side.

Unlike the previous model, the battery does not have sleek curves, offering a practical shape with venting all sides for a bright green LED strip and cooling.

The weather rating (IP rating) is IP56. However, installation in an area away from direct sunlight is advisable, like in a sheltered area like a garage or carport.

Comes with a Battery Inverter

Tesla Powerwall battery is an alternating current battery and comes with an integrated AC-DC charger or inventor. The peak output of seven 7kW and inverter power is high, with a constant output of five kW. High output is suitable for a home with many appliances running at the same time. The high peak rate is seven kW for ten seconds. That means this battery is suited for short power surges.

Liquid Cooled

Tesla Powerwall is the only solar battery on the market that integrates liquid cooling, allowing the battery to operate at different temperatures. Power derating is a common phenomenon with many lithium-ion based solar batteries. With the liquid cooling feature, the battery releases a lot of heat under high loads and quick charging. It results in improved performance at high temperatures as well as a longer lifespan.

Performance Metrics

Tesla Powerwall has a DoD of one hundred percent. It is also safe and has a roundtrip efficiency of ninety percent.

The Fortress Power eVault

The Fortress Power solar battery uses Lithium Ferro Phosphate technology that is safer than a lithium-ion battery. LFP technology is new, and it looks promising. The huge size (18.5 kWh) of the solar battery has a low cost per kilowatts per hour.

Additionally, the battery has wheels and is self-contained. That means you can install your battery yourself with ease and roll the battery around easily.

The LTP technology also allows the battery to last for up to six thousand cycles. It is twice the NMC technology in Tesla Powerwall batteries.

Pika Energy Harbor Smart Battery

A Pika Harbor Smart battery is a perfect option to integrate with your solar panel, particularly if a homeowner wants to backup their home's power, demand charges, or utility has no or reduced net metering.

When the solar panel produces more electricity than you require, the excess power is stored in your battery rather than sending it back to your electric grid. When the panel is not producing adequate power, a homeowner will use the electricity in their battery.

Pika Energy batteries are designed to integrate energy storage and solar photovoltaics effortlessly. It has a flexible solar storage system that gives your home adequate storage, instantaneous power, and solar to offer electricity during power outages.

The batteries were designed for two markets. The first is areas with time-of-use electricity rates like California, where electricity costs at daytime when demand is high. The second market is zero export, where homeowners cannot export any extra solar electricity to their grid.

Your battery system pairs with a solar panel installation to store power in your home, offer backup power, and manage energy costs. You can install it as part of your new solar panel or add it to a solar panel system which uses a Pika Island Inverter.

The battery comes in two (2) sizes, namely:

  • Harbor Flex solar battery with a storage capacity of 11.4 kWh
  • Harbor Plus battery with a storage capacity of 17.1 kWh

The inverter used in the battery system can handle a maximum of sixty-eight kWh of storage. Therefore, you can install other batteries to improve your home storage capacity.

The battery has a ten-year warranty. If the solar battery system malfunctions during the warranty period, you can replace the product per Panasonic's battery warranty.

Find a Solar Battery Installation Company Near Me

Even batteries with almost identical specifications could have different performance and lifespan. Purchasing the appropriate battery for your solar system means a long lifespan, high performance, and low maintenance. You will be able to use solar energy when your solar panel isn't producing energy, particularly at night. At Sun Solar Electric, we invite you to speak with our competent team of solar power installers to explore the best battery for your home solar system in the Bay Area and Northern California. Call us at 707-658-2157 to book your initial consultation.

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