LG CHEM RESU 6.4EX VS TESLA POWERWALL


How does the LG Resu compare to the Tesla Powerwall?
If you are looking at a 6.4kWh Lithium-Ion battery for use in Australia right now, you are probably tossing up between a LG Chem Resu 6.4Ex and the Tesla Powerwall.
To help you decide which one is for you – here is a side by side comparison, and some commentary on their warranties below.
LG Chem Resu 6.4EX
$7,500
6.4kWh nominal storage
5.1kWh warranted

drops to 3.8kWh after 7 years
3.6kW steady, 4.6kW peak
single or 3 phase
no inverter included
10 year warranty
19.2MWh warranted throughput
warranty void at 50ºC ambient
 
Tesla Powerwall
$8,000
6.4 kWh nominal storage
5.4kWh warranted
drops to 4.6kWh after 2 years
drops to 3.8kWh after 5 years
3.3 kW, 5kW peak
single or 3 phase
no inverter included
10 year Warranty
18MWh warranted throughput
warranty void if avg temp > 30ºC

The most important numbers to consider when buying a battery, are the ones that the manufacturer will actually warrant. I’ve read both warranty documents in detail and here’s how they compare in terms of battery performance over 10 years:
Tesla PowerwallDespite the 6.4kWh nominal storage capacity, the Tesla is only warranted to give:

  • 5.4kWh over the first 2 years
  • 4.6kWh for the next 2 years
  • 3.8kWh for the final 5 years of the warranty

This gives a total of 16,000kWh of warranted energy output over the warranty period cycled once per day, or 18,000kWh if you cycle it more than once per day.
The low kWh for the final 5 years of the warranty is a definite disadvantage, and will cause disappointment for people who were hoping to cover 5-6kWh of energy consumption overnight for the life of the battery.
Here’s what the warranty looks like:

Warranted energy storage for the Tesla Powerwall.

Internet connection requirements
The warranty will be voided after 48 months if you don’t connect the Powerwall to the internet and register it within 3 months after the installation. Also your internet must not be down for more than 45 days following registration or the warranty is voided.

Operating Temperature
The warranty document does not explicitly give a temperature range for operation or storage – but it does say the battery must be used as per the user manual. The user manual says “The average ambient temperature over the system’s life should be 30°C or less”.  Kudos to Telsa for not voiding the warranty if the battery is occasionally subject to some of the extreme temperatures we get here in Australia.

LG Chem Resu 6.6 EXThe LG Chem battery is warranted to retain:

  • “at least 80% of Nominal Energy 6.4kWh for 7 years”
  • “and at least 60% of Nominal Energy 6.4kWh [for the following 3 years]”

This gives a total warranted throughput of 17,000kWh cycled once per day or 19,200 kWh if you cycle it more than once per day.

The warranty also stipulates that you should not discharge more than 1920kWh per year. If you do, then the warranted kWh is reduced on a sliding scale. I won’t go into the details here – you can read them in th warranty document. I suspect that the details of this will be irrelevant to most people as I’m guessing the Battery Management System (BMS) will be programmed to never breach the 1920kWh per year limit by default.
In the chart below, I’ve worked out the max number of cycles you can perform to stay under the warranted kWh as a % of nominal energy, and also keep under the annual kWh limit (1920kWh per year).

As you can see you certainly get the initially warranted energy storage, for longer, compared to the Powerwall.

LG Chem Resu 6.4EX warranted energy storage

Warranted Temperature Range
The battery warranty is voided if the battery operates below 0ºC or over 40ºC. I believe the battery has a temperature cut out switch that makes this impossible – unless you override the default software.
The warranty is voided if the battery is exposed to a temperature over 50ºC. So don’t keep it in an uninsulated garage or shed.

ConclusionBoth batteries are about the same price, give or take $500. Both warrant a similar amount of energy give or take 1,200kWh over 10 years.
The LG’s warranted energy is more consistent than the Powerwall’s, which will make it easier to design into your home, and predict savings.

The LG is definitely easier to install mechanically.

The LG is sold by the major wholesalers, so any installer can get hold of it. The Tesla is only available from a select few installers.

The LG can be expanded by 3.6kWh at a time. The Powerwall can be expanded by 6.4kWh at a time.

The Powerwall is more tolerant of extreme Aussie temperatures. You have to be careful not to expose the LG to more than 50ºC, and be aware that it will cut out automatically at 40ºC.

The total installed price of the LG will be lower because it is compatible with cheaper hybrid inverters. The Powerwall only works with Solar Edge on single phase and Fronius on 3 phase. This will change when the ~$1,500 SMA Sunny Boy Storage battery inverter is released.

My personal choice would be the LG. I value the more consistent, warranted kWh. It is more flexible in terms of inverter choice, installer choice, future expansion and installation location. Fully installed, it works out a couple of thousand dollars cheaper. And I have a well insulated garage, so I’m confident it won’t get too hot.

But if you are not confident that you can keep the battery under 40ºC then the Powerwall looks like a better choice.

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