In this article we’re going to look at Tesla’s Powerwall versus LG’s Chem RESU head-to-head to see how they stack up.

If you had told us five years ago that an electronic appliance company would face off against the world’s leading electric vehicle startup, we would have said you’re dreaming. 

As unlikely as it is, the home battery market is now led by LG’s subsidiary, a chemicals company called LG Chem, and Elon Musk’s moonshot Tesla. 

The two companies from starkly different origins have made Australia one of their primary battlegrounds, competing on price, performance and market share. 

Luckily for homeowners, this only means lower prices, better technology and more secure warranty offerings. 

As it stands, LG Chem is leading the pack with a market share of 30%, while Tesla follows behind with a 14% share. 

Yet Tesla has always dominated the headlines. Everytime Elon lifts his little finger, the world no doubt hears about it.

So it’s clear that both of these heavy hitters are here to stay, but, if you’re a homeowner it’s probably not obvious who you should choose. 

Do you have an existing solar system? Planning to go off grid? How much energy do you need? All this and much more can affect which battery is best suited for your home. 

To help you out, we’ll break down the data and show you which battery is best in which areas, so you can make the right decisions and get the best return. 

Battery Capacity

The first thing that stands out, and, in fact, is front and center in most people’s mind, is each battery’s respective size. 

While earlier generation batteries on both sides were capped at 6.4kWh, both Tesla and LG Chem have upped the capacity of their units substantially. 

Tesla takes the cake as the largest battery, with a total capacity of 13.5kWh. LG Chem, on the other hand, has a capacity of 9.8kWh. 

For many people, a larger battery is all they are looking for. More capacity means more energy stored for later use, and in turn, a better ROI. 

That being said, the LG Chem RESU packs a bigger punch. 

Battery Output

While the Powerwall has a total output 3.3kW, the LG Chem RESU has a power output of 5kW, with the potential to go up to 7kW for short periods. 

What does that mean for your home? Well, a larger output means that the battery is able to supply more power at any given time. 

Therefore, if you decide to switch on a number of appliances requiring more than 3.3kW, the Tesla Powerwall would not be able to provide enough power to support your home’s entire load. 

Battery Efficiency

The efficiency of a battery refers to the batteries ability to store energy, discharge it, and have it reach your home’s circuits without being lost. 

Every electrical component has some innate resistance, so unless your home is run on superconductors, it is impossible to achieve 100% electrical efficiency. 

The LG Chem RESU, for example, has an electrical efficiency of 95%+. Therefore 95% of the solar energy stored in your battery will be passed onto your home’s appliances at a later time. 

The Powerwall on the other hand has an efficiency of 90%.This 5% difference will add up over time. 

That’s because 5% of 13.5kWh is 675W, and if you cycle your battery once a day, you will end up losing just under 2500 kWh over a ten year period. 

Depth of Discharge

Depth of discharge (DoD) refers to the percentage to which the battery can be drained before it stops providing power. 

Most homeowner’s assumption is that home batteries are drained to empty every time, but for most batteries this is not the case. 

That’s because the less the battery is drained each time, the greater the battery’s lifespan. 

The Powerwall for example, has a 100% depth of discharge (something which is fairly uncommon), whereas the RESU has a DoD of 95%. 

For some, a greater depth of discharge is preferable as it allows them to get more out of each and every cycle. 

Others prefer to increase a batteries lifespan by reducing the DoD. 

There is no clear winner in this instance, as it is really a matter of opinion and preference. 

Battery Size and Dimensions

This depends on whether you would prefer a large, wall mounted battery to show off to your neighbours, or a smaller, more inconspicuous unit. 

If you’re someone who appreciates good design and needs their battery front and center, then the Powerwall is for you. 

The Powerwall is exceptionally large, standing about 1.15 m off the ground with a width of 0.75m. 

When wall mounted, the Powerwall is a sight to behold. 

On the other hand, the RESU is far more energy dense, packing nearly 75% of the Powerwall’s capacity into a battery less than half its size. 

The RESU stands just under 0.5m tall, with a width of 0.45m. 

Thanks to the RESU’s ‘stack and fold’ cell configuration, it is able to pack a lot more energy into a smaller space. 

Weather Resistance

Most Australian homeowners have to take extra precaution when purchasing solar and storage equipment. 

Why? 

Because most countries don’t encounter the severe weather we do, so we need products that can stand the test of time—and the test of our hot summer days. 

Thankfully, both companies have taken this into consideration and provided a temperature rating of up to 40C. 

The Powerwall does, however, have a better temperature minimum at -20C, whereas the temperature minimum for the RESU is only 0C. 

Battery Warranty and Lifespan

Many homeowners are often confused as to how long a battery really lasts. And, most of the time, the question is not answered in a clear way. 

As Lithium-Ion batteries are cycled, their capacity is reduced. For example, a LG Chem RESU can undergo around 6000 cycles before its capacity is reduced by 20%. 

Researchers suggest that lithium-ion batteries are safest when their capacity does not fall below 80% of their original size. 

After that, the battery is considered ‘dead’. Therefore a home battery’s lifespan is as long as it takes for that battery’s capacity to be reduced by 20% from continual cycling. 

Battery manufacturers, however, prefer to put a more exact deadline on their products as a vote of confidence and to limit their responsibility for damage. 

That’s why most battery manufacturers will provide a warranty for x amount of years in which they will be financially responsible for the product’s failure. 

After x years, the company stipulates that the battery has undergone too many cycles and if it fails, it is a result of ‘old age’ and overuse. 

By looking at a company’s warranty, we can get an indication of how long the company expects their battery to perform. 

Both Tesla’s warranty and LG Chem’s warranty are valid for ten years. However, Tesla stipulated that they wouldn’t cover ‘usual wear and tear that comes with operating the battery’.

Many have argued that this language is far too vague and could include any number of things. 

Whereas LG Chem had no such clause included in their warranty. 

Internal Inverter Vs External Inverter

One major difference between these batteries is how they connect to your system. 

On one hand, we have the LG Chem RESU, which is a standalone battery, requiring a hybrid or battery inverter to be added to your system for it to function, meaning it is DC coupled. 

The Tesla Powerwall, however, has an internal inverter, meaning that it is AC coupled to your solar system. 

What does this mean? 

If a component is DC coupled, it means that it uses DC power.

For example, a DC coupled battery which shares an inverter with your solar array can receive DC power directly from your solar system, without being converted. 

An AC coupled battery means that at some point the battery converts its power to AC before exporting it. 

An AC coupled battery is not directly linked to your solar panels or inverter, but runs through your meter box directly. 

The downside of this is that to store power, the electricity needs to be converted twice: once to take the DC power from your solar panels to the inverter, and then back again to DC before being stored in your battery. 

This results in a lower efficiency and greater power loss. 

However, if you already own a standalone solar system, then an AC coupled battery is far easier to install, as it does not require an external inverter. 

Conclusion

Both batteries show promise, and both have proved themselves in the market. 

While Tesla’s Powerwall wins the prize for the largest capacity, it seems LG has a cell technology that has resulted in a higher efficiency and energy density. 

When it comes to DoD, once again Tesla wins over LG Chem RESU with a 100% DoD. 

However, if you are looking for a longer lasting battery, then look to the LG. 

Both batteries will ensure that your home experiences lower bills and greater energy independence, and it really comes down to how you’d like your battery connected. 

The LG is great for homeowners who don’t yet own solar, and are looking to install a hybrid system all at once, given that it is DC coupled. 

The Tesla Powerwall, on the other hand, is better suited for homes that own solar already and are looking to retrofit a battery to their existing system. 

Really, it’s up to you, the homeowner! 

Next Steps…

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