jrweiss98020
Tessa's Tesla
First, will you be able to run your air conditioners and nominal house loads on 2 Powerwalls? You can get 5kW continuous (7kW or 7.2KVA peak) from each PW. Startup loads on air conditioners can be twice the running loads. Each EV can take up to 9.6kW when charging. How many miles will you drive? Estimate 0.3 kWh/mi for charging. If you lose the grid at night or on a cloudy day (no PV) when the A/C is running and 2 cars are plugged in, can you disconnect the cars fast enough to keep the PWs from shutting down? What will your new water heater draw? Even the new heat pump types use resistance heat during peak loads.Perhaps a dumb questions, but why the bigger system and 3 powerwalls?
If I were to assume 8 months to be 650kWh and 4 months to be 1000kWh, it'd be 9,200kWh/year. How much would another EV add and then changing a gas water heater to electric?
Tesla 9.6kW system is projecting 14,394kWh/year, which would be an excess of 5,194kWh/year from the 9,200kWh/year assumption we calculated above
Tesla 12kW system is projecting 17,562kWh/year, which would be an excess of 8,362kWh/year from the 9,200kWh/year assumption we calculated above
What is the benefit for all of this excess and adding 3 powerwalls instead of 2?
The larger system will help future-proof your house when you add all those new high-draw appliances/cars. Any load that the PV can't supply will be borne by the PWs or grid. With a grid outage, you will have to closely monitor your loads with 2 PWs.