Financial analysis PV plus powerwall versus PV only

[winfield100]

Is there an analysis of PV plus powerwall versus PV only?

I'm trying to justify 1-2 powerwalls as we have "only" lost power for 4 days (hurricane Irma) and 11.25 days (hurricane Ian) from hurricanes since 2017
Does anyone have any spreadsheets or similar to give an analysis of the above or a link to or a discussion of similar please

 

[ucmndd]

A powerwall will essentially never make sense on a purely financial basis in Florida.

 

[ewoodrick]

Is there an analysis of PV plus powerwall versus PV only?

I'm trying to justify 1-2 powerwalls as we have "only" lost power for 4 days (hurricane Irma) and 11.25 days (hurricane Ian) from hurricanes since 2017
Does anyone have any spreadsheets or similar to give an analysis of the above or a link to or a discussion of similar please

This is easy!

How much were you willing to pay for power after Hurricane Ian?

(and unless properly sized, don't assume that 2 PowerWalls can last for a day or even power the Air Conditioners)

If you aren't talking about power failures, then you'd be talking about storing unused energy created during the day for later that evening.

 

[spsheridan]

Is there an analysis of PV plus powerwall versus PV only?

I'm trying to justify 1-2 powerwalls as we have "only" lost power for 4 days (hurricane Irma) and 11.25 days (hurricane Ian) from hurricanes since 2017
Does anyone have any spreadsheets or similar to give an analysis of the above or a link to or a discussion of similar please

Unlike solar panels, it's hard to justify a whole-home battery purely on the basis of electrical cost avoidance or recovery. If you're on a Time of Use plan where your electrical cost varies with time of day, then you can reduce your electrical costs by using the battery to provide energy to your home during the peak periods and draw from the grid during the less expensive periods. But this cost reduction will likely be minor compared to the cost of installing whole-home batteries.

I agree with @woodrick that the main justification for whole-home batteries would be to avoid the inconvenience of losing electricity during a grid outage. If you have electrical equipment that is essential to maintain life support for someone in your household or if you have large quantities of frozen/refrigerated products that you could lose in the event of a grid outage, then it's easier to justify a whole-home battery but cost probably won't be the reason.

 

[ewoodrick]

To put it a different way, I've got a $20,000 generator sitting outside that I hope will be a complete waste of money. But it will pay for itself if I have a multi-day outage.

It's an insurance policy.

 

[RKCRLR]

From a purely financial standpoint you are better off going for a backup generator. However, there is a lot to be said for the convenience of PV plus battery backup. A single battery will allow your solar to continue solar production while the sun is shining when the grid goes down. The switchover is practically seamless (you may go for a second without power during the switchover) and there is no maintenance involved like there is with a generator. You'll need to estimate how much battery storage you need to get through periods of no solar production. But if you want to go indefinitely with no solar production then a generator is the only way.

 

[Matt-FL]

I calculated my ROI on panels only, because like @ewoodrick mentions, I viewed the Powerwall as my generator replacement.
My ROI: originally figured 8 years 6 months based on when I ordered my system.
However, my utility raised prices considerably until a year later when Tesla finally installed, the ROI was down to 7 years 3 months.
In actual usage, it seems to be even lower. At my current savings, I'm figuring 6 years 6 months - if rates continue to stay where they are.
If I add in my powerwalls, I am at just about 10 years ROI, just when their warranty expires.