Long Time Solar Owner, new to Forum

[Stan Kromfols]

I had my Wattsun Dual Axis Tracker installed in 2004, with (16) 170 W panels, then immediately added an additional (4) 190 W panels, all with Enphase micro inverters. In 2009 I added (6) 260 W roof mounted panels on top of my hobby shop. Two years ago I ordered the Tesla Powerwall, which was finally delivered and installed about 6 months ago, and earlier this month I upgraded my Tracker and now have (15) Solaria 360 W panels. I have PG&E service and I'm still on the grid, but hopefully with my panel upgrade my service true up with be close to zero.

I just recently found this forum and look forward to exchanging information with other solar owners.

[Ampster]

............. I have PG&E service and I'm still on the grid, but hopefully with my panel upgrade my service true up with be close to zero.

I just recently found this forum and look forward to exchanging information with other solar owners.

Welcome.
Which rate plan are you on with PG&E? Have you figured out what load shifting with the Powerwall will do to your bill?

[Stan Kromfols]

Ampster, I'm on the Time of Use Peak Pricing 4 - 9 weekdays. I check my power production and usage with my Tesla app and find that I'm using no PG&E provided power during the high rate hours, because my Power wall supplies all of my power during that period. But since having my Power wall installed I've had my solar panels upgraded, so I haven't really been able to calculate my best options. What I'm looking at now if the proper operation of my tracker. As mentioned above, it's a dual action tracker and I believe that it's going into the horizontal mode too early so it's not getting the full advantage of sun early morning and late afternoon. I need to find information on the operation of the electric eye. Any suggestions ?

[scrambler]

I was looking at the Powerwall as a standalone backup system, and got curious about what it would save when used in Cost Saving mode.
In that mode, the battery charges during Off Peak hours, and is used as the primary source during Part Peak and Peak hours, allowing you to maximize off peak prices.

I had made a spreadsheet to evaluate Net Metering revenues with MCE and PG&E, so I repurposed it to make a simulation of the Powerwall in that mode.
If anyone wants to play with it, it is downloadable here:

https://1drv.ms/x/s!At3vMAQjaOZLkSGDXSS1_Te4gMtG?e=6hgfnB

For me, with a yearly consumption of about 8,600 kWh, and with the current PG&E / MCE EV2 rates, a single Powerwall represents about $400 saving over the $1,600 yearly electricity bill
Not a great ROI, but if you are buying for a backup solution in case of outages, at least you can get your money back overtime.
It would basically eliminates all of my Part Peak and Peak usage even if 50% is reserved to backup.

The spreadsheet also allows you to compare your costs between various rate plans
You download your last year hourly usage data from your provider, and enter the Rate schedule and prices, and it will show the cost and cost saving.
It also has variable for the battery capacity, how much you reserve for backup, and the battery charging losses.

[SunEagle]

I was looking at the Powerwall as a standalone backup system, and got curious about what it would save when used in Cost Saving mode.
In that mode, the battery charges during Off Peak hours, and is used as the primary source during Part Peak and Peak hours, allowing you to maximize off peak prices.

I had made a spreadsheet to evaluate Net Metering revenues with MCE and PG&E, so I repurposed it to make a simulation of the Powerwall in that mode.
If anyone wants to play with it, it is downloadable here:

https://1drv.ms/x/s!At3vMAQjaOZLkSGDXSS1_Te4gMtG?e=6hgfnB

For me, with a yearly consumption of about 8,600 kWh, and with the current PG&E / MCE EV2 rates, a single Powerwall represents about $400 saving over the $1,600 yearly electricity bill
Not a great ROI, but if you are buying for a backup solution in case of outages, at least you can get your money back overtime.
It would basically eliminates all of my Part Peak and Peak usage even if 50% is reserved to backup.

The spreadsheet also allows you to compare your costs between various rate plans
You download your last year hourly usage data from your provider, and enter the Rate schedule and prices, and it will show the cost and cost saving.
It also has variable for the battery capacity, how much you reserve for backup, and the battery charging losses.

That is pretty much what others have found concerning using a battery as an emergency power supply. Sad but until the price of any battery comes way down unless you are being charged very high rates by your POCO, batteries do not have any ROI.

[scrambler]

Sure but on the other hand a regular generator has zero ROI.
Buying a backup solution is an expense you agree to make to get the security during an outage.
At least with a system like the Powerwall, you can use that system for more than just emergency backup, and get "some" return on your investment.

[J.P.M.]

Sure but on the other hand a regular generator has zero ROI.
Buying a backup solution is an expense you agree to make to get the security during an outage.
At least with a system like the Powerwall, you can use that system for more than just emergency backup, and get "some" return on your investment.

For better reliability in emergency power outages, ROI probably is not a consideration.

For high(er) reliability of getting/having uninterrupted power during grid outages, a fossil fuel powered source will be less costly and have fewer considerations on use with respect to how long it can supply the required load.

Batteries have real promise, but as a practical matter, do not yet have the capability to supplant a fossil fuel fired generator for cost and applicability, at least for most residential applications in the developed world.

[SunEagle]

Sure but on the other hand a regular generator has zero ROI.
Buying a backup solution is an expense you agree to make to get the security during an outage.
At least with a system like the Powerwall, you can use that system for more than just emergency backup, and get "some" return on your investment.

I disagree that a generator has zero ROI. It has saved my food in the refrigerator and has kept my family cool and happy since they could still use their internet equipment.

Also to get the same amount of kw power from a battery would cost me many times what the 12kw generator and propane did.
What do they say about a family being happy. PRICELESS.

[scrambler]

That is what I meant
You buy a generator / backup solution for the invaluable service it renders in an outage, not to physically get your money back.

As for Gaz powered generator versus battery, it comes down to what one's preferences and priorities are...