How many Powerwalls is too many?

[Cobra281]

I recently had a 29.8 kw solar system installed. My highest production thus far has been 174 kwh in a single day with the lowest being during an April shower at 25 kwh.

I use about 150 kwh a day during the summer (about 30 or so of that is my MS). We have time of use plans where I am at, so I am looking to use the powerwalls for the shoulders, PV for the mid-day, and then charge the car/PWs at night.

I do have LED lights all throughout the house and I have read up on the flickering caused by the Hz issue.

Tesla's configurator says to shoot for 4 PWs. Considering all of the above, what say you?

 

[commasign]

I have a 20kW solar PV system (generating 110kWh/day peak, and we consume 75-100kWh/day) with 4 PowerWalls and it's enough to allow us to go off grid. For a 30kW system, maybe 5-6 Powerwalls if price isn't an issue.

 

[miimura]

There are two different sizing considerations.
1. How many kWh do you use when the sun isn't shining?
2. How big are the loads (in amps) that you want to use during a grid outage?

Personally, I don't charge my cars from the Powerwalls because my solar is relatively small and my Off-Peak power is relatively cheap. So, my Powerwall capacity is mostly used to satisfy my usage during the Peak hours from 2pm-9pm.

If you want to run A/C during a power outage after a hurricane, you need to make sure you have enough Powerwalls to deliver the start-up current required. Tesla generally won't install any load with a breaker size greater than 30A per Powerwall. Locked Rotor Amps is also an important spec to look at on your A/C compressors. You need enough Powerwalls to cover that amperage also. For example, if one A/C unit has a LRA rating of 120A, you need at least 4 Powerwalls (4 x 30A). Soft start accessory can sometimes reduce this startup demand.

 

[Cobra281]

Thanks for the tips. I'm going see how the quote for 4 looks. Should have it tomorrow.