sonnen eco: the complete battery review

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sonnen is one of the biggest names in energy storage technology, and in 2016 the company announced a new battery designed for home use: the sonnen eco. The eco is a fully integrated energy storage system that includes an inverter and smart energy management software. Property owners with solar that install a home battery like the eco are able to store excess solar electricity for use later in the day. As a result, properties with solar-plus-storage can increase their total monthly savings in certain markets. (Note: check out our review of sonnen’s other primary product line–the ecoLinx–here.)

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How does the sonnen eco work?

The sonnen eco is an ideal pairing for solar panel systems, especially if your utility has reduced or removed net metering, time-of-use rates, or demand charges. Installing an energy storage solution like the sonnen eco allows you to maintain a sustained power supply during the day or night.

As with other energy storage products, the sonnen eco is sized for day-to-day use at your home and is often paired with a home solar panel system. When your solar panels produce more electricity than you can use in your home, the excess is stored in the battery system instead of being sent back into the grid. Later, when your panels aren’t producing enough electricity to meet your home’s needs, you can use the electricity stored in your sonnen home battery instead of having to buy it from your utility company.

Key things to know about the sonnen eco

Sonnen describes the eco battery as an “all-in-one residential solar battery solution.” It offers various grid-tied functions, including increasing household solar self-consumption and managing time-of-use electricity rates for maximum savings on your electricity bill. The battery also has some backup power capabilities.

When evaluating solar batteries, there are various important metrics and technical specifications to keep in mind. Among the most important are the size of the battery (power and capacity), its chemistry, depth of discharge, and roundtrip efficiency

Size

The sonnen eco comes in seven different sizes with varying power and usable capacities. Power (measured in kilowatts, or kW) determines the maximum amount of electricity that can be output at a single time, while usable capacity (measured in kilowatt-hours, or kWh) is a measure of the maximum amount of electricity from your battery on a full charge.

Think of your battery like water running through a pipe. Energy capacity is the amount of water available to push through the pipe, while power is the size of the pipe itself. Larger pipes allow more water to flow through at once, which depletes the water faster. Similarly, a battery with a high power rating can deliver more electricity at one time, but will burn through its available energy capacity faster too.

sonnen eco power and usable capacity by model

ModelPowerUsable capacity
eco 53 kW5 kWh
eco 7.54 kW7.5 kWh
eco 108 kW10 kWh
eco 12.58 kW12.5 kWh
eco 158 kW15 kWh
eco 17.58 kW17.5 kWh
eco 208 kW20 kWh

A battery’s power determines what appliances you can run with it at once, while usable capacity determines how long those appliances can be run. Batteries with a higher power rating are capable of powering more robust appliances or many appliances at once, while batteries with a higher usable capacity can store more total energy and thus can run your appliances for longer periods of time without needing to recharge.

Basic functionality

The functionality of one solar batterie next to another can vary; some batteries boast of superior off-grid capabilities, while others offer software solutions for rate arbitrage. Here are some of the most important qualities of the sonnen eco:

Coupling

The sonnen eco is an AC-coupled battery; this means that in a solar plus storage system, direct current (DC) electricity flows from solar panels to a solar inverter that transforms the electricity into alternating current (AC) electricity. That AC electricity can then flow to your home appliances, or go to another inverter that transforms the electricity back to DC for storing in a battery system.

ac coupled battery system diagram

Backup power

The sonnen eco comes with backup power capabilities. Most solar batteries require an external transfer switch to allow for off-grid operation; however, the sonnen eco has a built-in automatic transfer switch. This means that with the correct power electronics set up, your sonnen eco system can automatically power your home appliances when the grid goes down.

Chemistry

The sonnen eco is a lithium-ion storage product; specifically, it is a lithium iron phosphate (LFP) battery. Relative to other types of batteries, LFP batteries are known for their high power rating and safety – to learn more about how different lithium-ion battery chemistries stack up against one another, check out our overview of battery chemistry differences.

Performance metrics

Two key ways to evaluate the performance of a solar battery are its depth of discharge and roundtrip efficiency

Depth of discharge (DoD) indicates the percentage of a battery’s energy that has been discharged relative to the overall capacity of the battery. Because the useful life of a battery decreases each time you charge, discharge, and re-charge it, many battery manufacturers specify a maximum DoD level for optimal battery performance. In general, batteries with a higher depth of discharge are considered higher quality products. The sonnen eco line boasts a depth of discharge of 100 percent across all battery sizes.

Roundtrip efficiency is a measure of the electrical losses involved with charging and discharging a particular battery. The higher the percentage, the more efficiently the battery is able to convert incoming electricity into stored electricity and then back into usable electricity. All batteries in the sonnen eco line have a roundtrip efficiency of 86.0 percent; this means that for every 10 kilowatt-hours (kWh) of electricity you put into the battery, you’ll receive 8.6 kWh of output.

Sonnen eco warranty coverage

sonnen eco warranties

  • Warranty period: 10 years
  • Warrantied cycles: 10,000
  • Guaranteed end of life capacity: 70%

In most cases, homes with a sonnen battery will charge and drain the battery every day. The eco comes with a 10-year, or 10,000 cycle, warranty. Sonnen guarantees that the battery will maintain at least 70 percent of its capacity to hold a charge during that time.

Sonnen battery technology is similar to other rechargeable batteries both large and small: as time goes on, the battery loses some of its ability to hold a charge. Think of how the battery life of a brand-new smartphone compares to one that is a few years old. As you continually charge and drain your phone’s battery, it starts to lose some of its ability to hold a charge.

The battery life of your eco battery will deteriorate in the same way. That isn’t an indicator of a product flaw – all batteries lose some of their ability to hold a charge over time, whether it’s an electric vehicle battery, a home energy battery, or a rechargeable AA battery. This is why Sonnen offers a warranty that guarantees a certain amount of storage capacity.

Warranty, capacity, and power are three of the most important metrics you should consider when comparing home battery options. If you’re curious to learn more about the best way to perform your own battery comparisons, check out our video explaining how to evaluate your home energy storage options:

If you want to compare individual battery models side-by-side, our battery Buyer’s Guide lets you select products and compare them based on efficiency, capacity, power, and more.

How much does the sonnen eco cost?

The Sonnen eco has a starting list price of around $10,000, which includes an integrated inverter and energy management software. However, the price doesn’t include installation, which can increase your costs by thousands of dollars.

If you want to install the eco as part of a solar-plus-storage system, battery costs are just one part of the equation. An average 5 kilowatt (kW) solar energy system costs anywhere from $9,000 to $15,000 depending on where you live and the type of equipment you choose.

That may sound like a lot of money, but installing a solar-plus-storage system can be a worthwhile investment. Whether or not the sonnen eco makes sense for you is determined by the way that your electric utility structures its rates, as well as your reasons for installing a solar battery.

In some cases, depending on where you live, you may have access to financial incentives that can reduce your home energy storage installation costs. For instance, if you live in California, you could get a cash rebate that covers most of your home battery costs through the Self-Generation Incentive Program (SGIP). Other states (like Massachusetts) are in the early stages of evaluating potential energy storage performance incentives as well, and several states already provide cash rebates.

Can you go off-grid with the sonnen eco?

Installing a solar-plus-storage system at your home is a great way to take control of your electricity bill, but it doesn’t mean that you’re completely disconnected from your utility. Going “off the grid” with solar batteries is actually a more expensive and complicated proposition than you might think. Most home batteries, including the eco, only have enough capacity to store a few hours of electricity. That being said, some of the larger eco batteries could serve as temporary backup when the grid goes down if you have a solar panel system to provide power.

Where to buy the sonnen eco

sonnen’s eco battery is currently available through the company’s installer network in the U.S. Whether you want to install a sonnen eco or other home battery pack, you will most likely need to work through a certified installer. Adding energy storage technology to your home is a complicated process that requires electrical expertise, certifications, and knowledge of the best practices required to install a solar-plus-storage system correctly.
A qualified EnergySage-approved company can give you the best recommendation about the Sonnen home battery and other energy storage options available to homeowners today. If you are interested in receiving competing installation quotes for solar and energy storage options from local installers near you, simply join the EnergySage Solar Marketplace today and indicate what products you’re interested in your profile’s preferences section.

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About Jacob Marsh

Jacob is a researcher and content writer at EnergySage, where he focuses primarily on current issues–and new technology!–in the solar industry. With a background in environmental and geological science, Jacob brings an analytical perspective and passion for conservation to help solar shoppers make the right energy choices for their wallet and the environment. Outside of EnergySage, you can find him playing Ultimate Frisbee or being ultra-competitive at a new, obscure board game.

5 thoughts on “sonnen eco: the complete battery review

  1. Mike

    I’m just wondering how a homeowner can have a 5kw solar system installed for $9,000 or $1.80/kw? No way anyone can run a sustainable business this way. The industry fluctuates from companies offering as low as $2.50/watt for turnkey solutions to $8+/watt. The reality is neither of these extremes is healthy for an industry to survive. Solar companies can not survive and deliver a solid product when they have to sell at prices under $3/watt. They will have to cut corners to barely make it and then have to fold their companies because it can not afford the warranties it has provided. On the other hand, solar sales people and companies that sell at the other extreme end of $7-9/watt (this is very common btw as well) is not sustainable from a consumer standpoint. I hope the industry can learn to operate in a healthy sustainable way where both the consumers and service providers of these products can both succeed. I hope these extremes which are misleading and harmful to both the industry and it’s consumers can stop because this really can be a win win for everyone involved.

    Reply
  2. Anil

    I too have a sonnen and I have observed the some of the issues as Frank. Having said that, I only wished that I had purchased a larger battery bank and sacrificed for a smaller pv system. The utility is not going to give us the maximum benefit of the energy produced and they will continue to marginalize the homeowner.

    Going with a larger capacity battery bank would be my recommendation to all. Also, don’t fill up your roof with panels, I have panels where the angle is just not optimal all year round and thus unable to maximize the capacity.

    The software and apps could and should be better, but the technology I think is the best available. Their documentation is wanting and many of the certified installers are electricians and can’t speak to all of the technology. Hopefully the competition will catch-up and provide us with equally compelling alternatives.

    Reply
  3. Frank Mueller

    Hi, I have had a Sonnen 12.5kw battery back up system since July or so. There are problems with this system:
    1. You can’t change the state of back up remotely. For example, if you are on vacation and you hear that a PSPS is planned at home, you can’t change that setting unless you are in the same WiFi location as your installation.
    2. If one battery fails (as ours did) the whole system goes down and they are not quick to respond
    3. The Sonnen will go out 3 times in the morning to energize the invertors to see if there is solar power being produced, using battery energy each time. By the third time is checks the battery is likely to be out of reserve power and you will have no power whether the sun is shining or not!
    4. There is no system to notify you by email or text that power is down, battery has failed or is critically low on reserve power, or other problems. Even my security system does that!
    There are other problems, too.
    Are these problems seen with all battery systems?– Tesla and others?

    Reply

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