Powerwall installation

[ShoeHo]

Hello. I was unable to get Tesla solar panels due to my roof type, but I am getting a Powerwall. The solar company told me I have to choose 6 circuits for backup. I’m not an electrical person and could use some help. I have a 10kW system and I thought one Powerwall was sufficient for 9.6.

Thanks!

 

[jjrandorin]

Hello. I was unable to get Tesla solar panels due to my roof type, but I am getting a Powerwall. The solar company told me I have to choose 6 circuits for backup. I’m not an electrical person and could use some help. I have a 10kW system and I thought one Powerwall was sufficient for 9.6.

Thanks!

If the question is "I thought 1 powerwall would provide whole home backup for my 10kW solar install" the answer is no, it wont provide whole home backup for that. You would likely need 2 powerwalls, but could need more depending on your electrical service size, what devices you have etc.

The most likely correct answer is to believe the solar installer who has already reviewed your system, etc, so either choose the number of circuits they mention (and understand that none of them will include 240 items like AC, electric ovens, Electric Dryers or any other 240V circuit) or order another powerwall.

 

[arnolddeleon]

You can certainly backup a whole house with one Powerwall. The problem is most people are confused by the fact that there two "size" things that you need to think about. One is peak power, this determines what is the largest load that you can run. As analogy, if we think of a Powerwall as tank holding water then this is how fast you can pull water from the tank. The other is energy storage (if you are thinking of it as tank, how many gallons that it holds).

A single Powerwall roughly has 14 kWh of usable energy. You can pull at around 5kW so this means if you were pulling at that rate you will empty that Powerwall in roughly 2.5 hours. On the other hand at 1 kW it will last for 14 hours.

The other thing that installers think about is how system is wired. In some situations the cheapest and easiest thing to do IS to backup the WHOLE house even if you only have one Powerwall. This is usually the case if there is convenient place to interrupt the wiring between the main breaker and load center. The other case where this is easy when the installer using the "backup switch" that goes at the meter base.

If you have the other situation where it isn't easy to backup everything then you have to choose which circuits then the number is usually limited because it takes time (and therefore more money) to move each circuit. The load center that can be built-in the Powerwall has a limited number of slots but you can always choose to have an external load center and move as many circuits as you want, just a matter of money.

Now, in either case you are limited by ratings of the Powerwalls that you have.

 

[ShoeHo]

If the question is "I thought 1 powerwall would provide whole home backup for my 10kW solar install" the answer is no, it wont provide whole home backup for that. You would likely need 2 powerwalls, but could need more depending on your electrical service size, what devices you have etc.

The most likely correct answer is to believe the solar installer who has already reviewed your system, etc, so either choose the number of circuits they mention (and understand that none of them will include 240 items like AC, electric ovens, Electric Dryers or any other 240V circuit) or order another powerwall.

Thanks. I have asked the solar installer to work with me to discuss this, just seeking outside opinions. I am NOT an electrical person!

 

[ShoeHo]

You can certainly backup a whole house with one Powerwall. The problem is most people are confused by the fact that there two "size" things that you need to think about. One is peak power, this determines what is the largest load that you can run. As analogy, if we think of a Powerwall as tank holding water then this is how fast you can pull water from the tank. The other is energy storage (if you are thinking of it as tank, how many gallons that it holds).

A single Powerwall roughly has 14 kWh of usable energy. You can pull at around 5kW so this means if you were pulling at that rate you will empty that Powerwall in roughly 2.5 hours. On the other hand at 1 kW it will last for 14 hours.

The other thing that installers think about is how system is wired. In some situations the cheapest and easiest thing to do IS to backup the WHOLE house even if you only have one Powerwall. This is usually the case if there is convenient place to interrupt the wiring between the main breaker and load center. The other case where this is easy when the installer using the "backup switch" that goes at the meter base.

If you have the other situation where it isn't easy to backup everything then you have to choose which circuits then the number is usually limited because it takes time (and therefore more money) to move each circuit. The load center that can be built-in the Powerwall has a limited number of slots but you can always choose to have an external load center and move as many circuits as you want, just a matter of money.

Now, in either case you are limited by ratings of the Powerwalls that you have.

Thank you, this was a really useful explanation.

I'm OK not powering my AC. I would like my refrigerators, lights, and outlets to stay working in an outage. Does that seem feasible?

 

[jjrandorin]

Thank you, this was a really useful explanation.

I'm OK not powering my AC. I would like my refrigerators, lights, and outlets to stay working in an outage. Does that seem feasible?

It sounds feasible, depending on what circuits they are on. All that stuff (fridge, lights, outlets) are regular 120v electrical appliances. How long they would work, would depend on what your home load is. You also would not be able to run any AC units, electric ovens, electric dryers, and likely your home heating units either.