Battery comparison Tesla Powerwall 2 CPS ESS 4kw/10kwh CPS ESS 8kw/20kwh
Capacity kwh 13.2 10.24 20.48
Whole home backup no yes yes
EV charger included no yes yes
Battery size extendable no yes yes
Secondary power input no yes yes
Switch time to backup 5 sec + <50millisec <50millisec
Max continuous power kw 5 4 8
Burst power kw 7 10 20
Grid tied max continuous power kw 5 12 12
Charge EV in backup mode no yes yes
Battery voltage 50V 54V 54V
Grid-tied yes yes yes
Charge battery from solar yes yes yes
Charge battery from grid no yes yes
Battery feed grid yes yes yes
Solar inverter included no yes yes
Weight kg 122 152 220
stackable yes yes yes

We’re often asked why CPS ESS is preferable over a Powerwall 2.  The main reason customers choose the CPS ESS system is that it provides a simple whole home backup system – since the system can handle up to 12kw (50A) in grid-tied mode and 50kw (200A) with an ATS, we can provide ANY home with a complete power system that can run ALL normal home loads in grid-tied mode, and even perform EV charging during power outages. The switch from grid-tied to battery/solar power is so fast customers can’t tell when it happens – whereas the Powerwall has a several second delay before the battery kicks in – causing many appliances to loose their memory and can cause computer systems to loose data. The Powerwall 2 is limited to the 5kw continuous operation – a fraction of what the CPS ESS can handle in grid-tied mode. The CPS ESS also uses one inverter for the entire system – this simplifies the construction and provides higher overall efficiency – the solar->battery storage efficiency is over 96%.

For those considering going off-grid, the secondary power input provides a means to connect another power source to your system, such as a wind generator or an inverter powered by your EV. Modern EV’s can now provide typically up to 1.5kw continuously from the traction battery by routing through the 12V auxiliary system. This makes the entire traction battery available for emergency storage through the secondary power input. The CPS ESS system is vehicle to grid ready.

The CPS ESS can also have larger battery sizes for those considering off-grid applications or those adding storage to existing solar. Battery size can be increased in 10kwh increments, without incurring the additional costs of an inverter and associated electronics. Normally battery size 2.5X the solar size is ideal for storing enough energy from solar to operate off-grid one day to the next, when solar refills the battery. Example – for an existing 8kw solar system, you can add a 4kw/20kwh CPS ESS AC coupled system.

Charging battery from grid must be kept below 25% of total use to qualify for SGIP rebates.