All across Canada, renewable energy is becoming a priority. Home and business owners alike are undertaking green renovations to save money and protect the environment, and concepts like the solar energy battery bank can make it easier to do both. Tesla’s Powerwall (now in its second iteration) is one of the most recognizable solar energy battery storage systems on the market today, but it’s not the only one available to Canadians wondering how to reduce their carbon footprint. In this article, we’ll look at the Powerwall 2 and see how it compares to three other popular choices.
The Latest With Tesla & the Powerwall 2
If you’ve never heard of the Tesla Powerwall before, here’s the bottom line: it’s a lithium-ion battery system that stores solar energy from rooftop panels for later use. By drawing energy from the Powerwall during peak consumption hours, homeowners can theoretically save anywhere from approximately $700-1150 USD annually.
One issue with the original Powerwall was the time it took for the energy savings it provided to make up its significant up-front cost. One case study estimated that almost every user would require longer than the Powerwall’s 10-year warranty period to see their energy savings pay for the device and its associated costs (including panels, a compatible inverter, and installation fees).
The Powerwall 2 was released in the winter of 2019, with several significant improvements over the original.
- More than twice the storage capacity of the previous version, with the Powerwall 2 offering a set capacity of 13.5kWh.
- A built-in AC/DC inverter/charger, which allows for easier retrofitting in homes that already have solar power systems.
- A liquid-cooled battery, which is more resilient under high ambient temperatures than other batteries and currently the only one of its kind on the market.
- Best of all, the Powerwall 2 is only nominally more expensive than its predecessor, allowing it to provide a 30% reduction in price per kWh over the first model.
There are some drawbacks as well. For instance, using an AC-coupled battery means that a small amount of power is lost during the conversion back and forth from DC to AC while the system operates. As such, systems that rely on AC-coupled batteries are slightly less efficient than DC battery-based alternatives, with the Powerwall 2’s round-trip efficiency estimated to be 89%. It’s also worth noting that the Powerwall 2 requires an additional solar inverter in order to work with a solar array, despite its built-in inverter/charger (which is why it works best as a retrofit to homes that already have solar infrastructure).
Powerwall 2’s Competition
All that said, Tesla isn’t the only company playing the solar battery game anymore. Consumers intent on comparison shopping may also find the following products to be valuable alternatives:
LG Chem Residential Energy Storage Unit
The first thing to note about the LG Chem RESU is that it’s a DC-coupled battery system. This means it needs to be used in conjunction with a compatible inverter, which can drive up initial costs even though the RESU itself is cheaper than the Powerwall 2 by several thousand dollars. However, the sheer abundance of available hybrid and multi-mode inverters makes it easy to tailor the RESU for a wide range of installation types, making it a particularly versatile option. It also differs from the Powerwall 2 in several other ways:
- LG Chem RESU batteries come with a variety of storage capacities, ranging from 3.3-13kWh.
- As a DC-coupled battery system, the LG Chem RESU also has a slightly higher round-trip efficiency than the Powerwall 2 (approximately 96%).
In terms of output, the RESU and the Powerwall 2 are comparable. Both offer 5.0kW, with a maximum peak of 7.0kW. The warranty length is 10 years on both as well, although specifications differ on the certificates for each.
Like the Powerwall 2, the German Sonnen Eco is an AC-coupled battery system. That means it also needs to work alongside a separate inverter in order to be compatible with a solar array. The major differences between the Eco and the Powerwall 2 are as follows:
- The Eco is available in a range of storage capacities from 3.3-16kWh.
- The Lithium LFP battery in the Eco is considered safer and more stable than the Lithium NMC battery in the Powerwall 2, boasting a lifespan of up to 10,000 cycles.
- The Eco offers a maximum inverter power rating of 3kW for single phase systems. It can provide 3.3kW for three-phase systems, but that still doesn’t compare favourably with the Powerwall’s offering of 5.0/7.0 kW.
Aquion Aspen 48S-2.2
This battery is something of an outlier on our list, since it’s the only one on this list to use salt water as the liquid inside. That certainly makes it safe — one selling point of salt water batteries is that they can be fully discharged without suffering any damage. However, using salt water for these batteries brings with it a few other considerations. Namely:
- The battery’s power output is much lower compared to the others (with a peak power output of 1kW for five minutes and only 400w continuous power over a 4-hour discharge)
- The lifespan of these batteries are much lower as well, with only about 3,000 charge cycles per unit.
- Since multiple batteries (10-12 on average) are needed to meet the needs of most homes, these systems also tend to be much larger and heavier than others.
As one reviewer in Australia pointed out, the Aspen 48S-2.2 may not even be the most environmentally friendly choice on this list, even with its innovative salt water technology. That’s because, even though these batteries produce fewer carbon emissions while being manufactured than most other models, they may produce more as a result of clean solar energy being lost as they charge and discharge during actual operation.
Choosing a Solar Energy Battery for Your Needs
At the end of the day, homeowners looking for a solar energy battery storage system would do well to determine their own priorities before deciding on one of the products mentioned above. Each of the four solar energy battery banks we’ve reviewed has its own unique strengths and weaknesses. To summarize:
- If you’re trying to retrofit a solar battery into a home that already has solar panels, the Powerwall 2 is still a great choice.
- If you want a system with slightly more round-trip efficiency and you don’t mind purchasing an external inverter for use with a DC-coupled system, the LG Chem RESU is an excellent alternative.
- If you want a DC-coupled system but battery stability is a top priority, you might want to go with the Sonnen Eco instead.
- If you have room for a larger setup and don’t need a system with particularly high power output, the Aquion Aspen 48S-2.2’s salt water battery is extremely safe and completely non-toxic.
Every home is different, so it’s best to consider what you need carefully before investing in a new solar battery system. Use the information in this article to make sure the battery you end up buying is one you’ll be happy with well into a cleaner and greener future