Better to use powerwalls or grid as my daily storage?

[RKCRLR]

I'm on EV2a, use the Advanced cost saving setting matched to the EV2a rate schedule, and have my Powerwalls set to a 50% reserve for outages.

On most days this allows me to power my house off the powerwalls from 3pm to midnight and recharge the powerwalls before 3 pm the next day.
My powerwalls were installed in June but I didn't get switched to EV2a until October.

My target is to have no excess generation where I'm paid $0.03/kWh for the surplus energy at True-Up. I'm probably going to overshoot this year. If I do, I'm going to do a combination of increasing my reserve and reducing the partial-peak hours in the app to reduce the number of cycles on the powerwalls. Hopefully, PG&E doesn't monkey with the rates to a point that I'm always chasing a $0 True-Up.

What would be interesting to see is cost analysis of a powerwall cycle vs the $0.03/kWh you are paid. I.e., are you better off reducing the powerwall life (and having to replace it sooner) to get the $0.03/kWh? I don't think so but I haven't seen the numbers. What would be really interesting is to see the $/kWh break-even point where you are better off paying for power than wearing out the powerwall.

 

[h2ofun]

I'm on EV2a, use the Advanced cost saving setting matched to the EV2a rate schedule, and have my Powerwalls set to a 50% reserve for outages.

On most days this allows me to power my house off the powerwalls from 3pm to midnight and recharge the powerwalls before 3 pm the next day.
My powerwalls were installed in June but I didn't get switched to EV2a until October.

My target is to have no excess generation where I'm paid $0.03/kWh for the surplus energy at True-Up. I'm probably going to overshoot this year. If I do, I'm going to do a combination of increasing my reserve and reducing the partial-peak hours in the app to reduce the number of cycles on the powerwalls. Hopefully, PG&E doesn't monkey with the rates to a point that I'm always chasing a $0 True-Up.

What would be interesting to see is cost analysis of a powerwall cycle vs the $0.03/kWh you are paid. I.e., are you better off reducing the powerwall life (and having to replace it sooner) to get the $0.03/kWh? I don't think so but I haven't seen the numbers. What would be really interesting is to see the $/kWh break-even point where you are better off paying for power than wearing out the powerwall.

do we have any real data about wearing out PW's?

 

[RKCRLR]

do we have any real data about wearing out PW's?

The Powerwall is warrantied for unlimited power cycles for 10 years in solar self consumption/backup modes. However, it is warrantied for 37.8MWh in aggregate throughput in all other modes. If the 37.8MWh were to be an actual life that means a Powerwall costs about $0.19/kWh of storage assuming a ~$7K replacement cost.

What that means that (if you believe the numbers) you are better off paying for electricity if the difference between the peak rate and base rate is less than $0.19/kWh.

I suspect the Powerwall will last longer than 37.8MWw but I don't know what the real data says or if any better data is available.

 

[Redhill_qik]

The Powerwall is warrantied for unlimited power cycles for 10 years in solar self consumption/backup modes. However, it is warrantied for 37.8MWh in aggregate throughput in all other modes. If the 37.8MWh were to be an actual life that means a Powerwall costs about $0.19/kWh of storage assuming a ~$7K replacement cost.

What that means that (if you believe the numbers) you are better off paying for electricity if the difference between the peak rate and base rate is less than $0.19/kWh.

I suspect the Powerwall will last longer than 37.8MWw but I don't know what the real data says or if any better data is available.

37.8MWh would be an average of 10.3kWh per day over 10 years. Since PW hold 13.5kWh that's a 76% discharge or a reserve limit of 24%.

 

[Odobo]

37.8MWh would be an average of 10.3kWh per day over 10 years. Since PW hold 13.5kWh that's a 76% discharge or a reserve limit of 24%.

So basically Tesla guarantee the PW will be able to fully charge and discharge everyday for 10 years assuming reserved is set at the default 20%....

 

[jjrandorin]

So basically Tesla guarantee the PW will be able to fully charge and discharge everyday for 10 years assuming reserved is set at the default 20%....

......while retaining 70% of its original capacity.

 

[RKCRLR]

So basically Tesla guarantee the PW will be able to fully charge and discharge everyday for 10 years assuming reserved is set at the default 20%....

Actually, it is guaranteed for unlimited cycles for 10 years to not fall below 70% in solar self consumption/backup modes. So, if you don't care what happens after 10 years, you could set the reserve to 0% and run it into the ground.

My main concern is backup so I'd like to stretch the life as long as possible.

 

[skepticcyclist]

Can 1 powerwall still power the whole home when there's no power outage (including hybrid water heater, induction cooktop) until it uses all its stored energy, and if there's a power outage then it will only power the lights, plugs and small 120v appliances? Or, can only 1 powerwall only be used with the lights, plugs 120v appliances that are wired to it even if there is no power outage?

One PW is plenty to power my entire home, but all of our appliances are gas (except the central AC). Gas furnace, water heater, stove/range, and drier. Minimal electricity used to just run the blower on the furnace and motor on the drier