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How many PW2?

How many PW2?

Hello, all!
I have been part of Tesla family for several years now: we own stock since 2014, have Model S, last year we ordered solar and PW2. We are located in Northwestern suburbs of Chicago.
Solar installation took place last March and it felt like abortion... But we moved on and are happy with our 8.5kW system (black on black). It’s been providing more energy that we expected actually.
Three weeks ago Tesla contacted us with documents to sign on one PW2 - this is what we ordered last year in September. We noticed that our deep well pump would not be able to be backed up with just one PW2. I called and asked how many PW2 we would need in order get deep water well backed up and I was told “probably 2”. I asked for a quote and they came back with 4 PW2 for $37Gs with installation. I thought it was an overkill and called again and asked for 2 Powerwalls (again). They came back with a quote ($17Gs) but claimed our deep water well pump would still not be backed up! My issue is, there was never a technician at our house to really look into what we need.
My question to you guys (perhaps TeslaDavid) is, what do you have backed up with 2 PW2?
Here are our larger power consuming devices:
1. deep water well pump (it peaks at 2.2 kW when it switches on - I don’t know exact make and model)
2. sewerage grinding pump (13 AMPs)
3. York gas furnace with a fan (15 AMPs)
4. York AC unit (20 AMPs)
5. Tesla wall connector

Any advice?

Thanks!

zoomerdog | 27. Juli 2019

You need to convert your usage to kWh. Each PW2 will generate 5 kWh, so 2 units will produce @ 10kWh. However, if you exceed the 10kWh, the PW will shut down and reboot.
Having said that, if your demand is 5.0 kWh , and you have 2 walls, you will have power for approximately 4.5 hours (22 / 5). Each wall will store 11 kWh, or 22 kWh for the two of them.

For perspective, in our house our energy demand with no AC is @ 1kWh. With 1 AC unit on, it jumps to 3.5 kWh.

Lastly you might consider an energy management system such as Energy Sentry. I've set the demand limit in my house in the summer months to 8.5, and it works perfectly and there is no danger of the PW rebooting since the limit is set at 8.5. http://energysentry.com/PP-residential-controllers.php

zoomerdog | 27. Juli 2019

Oops. My mistake. You need to determine your energy demand in kW, not kWh. Powerwalls will reboot if your demand exceeds 10kW

Sorry for the miscommunication

Tesla-David | 27. Juli 2019

@bigbrother, sorry for the late response. Just saw your post. In summary, we have a 13.2 kWh solar PV system, now supported by 2-PW2's. We live in a 2000 sq ft all electric home with electric heat pump, and heat pump water heater. We did an energy reduction retrofit (additional insulation, etc.) to reduce our energy consumption, swapping out old appliances for energy star ones, LED lighting. With this setup operating in self-powered mode we are operating independent of grid for ~9 months of the year, and only have to rely on grid from November - February to supplement our solar up in Edmonds, WA. We also charge two Tesla's (MS and M3) in our garage with two HPWC's. We are also sending back over 60 percent of our solar to grid. We are on net metering here, and our utility cuts us a check for $5k/year for our excess electricity sent to grid. Last year we paid $180 for our electricity for the entire year with the energy reduction retrofits. With our heat pump, we get air conditioning when needed, so we do not have a separate air conditioning system. Our setup works perfectly well to take care of our energy needs. Your electric draws do not appear to be exceptional. We stagger our EV charging so as not to overload the PW2 draws, and selectively operate our dryer which also spikes draws when on. We have not seen any significant problems in 14 months of operation with our PW2's. Your two PW2 system seems sized appropriately with your 8.5 kWh solar system. Good luck. We are blown away with how well ours have worked for us.

Tesla-David | 27. Juli 2019

One additional clarification, with our HPWC's, we limit the amperage to 25 A for our EV charging, so as not to overload the PW2 and keep the demand under 10 kW as @bob noted. We could up that to 30 A, but 25 A is sufficient giving us around 20-23 miles of charge/hour, which works for us (MS and M3 respectively).