Boy, do I have a lot of questions regarding adding a Powerwall to my existing Tesla Solar Panel system!

[OldPro]

Boy, do I have a bunch of questions about adding a Powerwall to my existing Tesla Solar Panel system! I placed my deposit and have started the preliminary process. We charge at primarily home for my wife's Tesla M3LR, we like the idea of having backup charging in case of a power interruption.
#1) Is the financial outlay worth it?

One of many questions.....

 

[miimura]

SDG&E has among the highest electric rates in the country. If anyone can make a Powerwall pencil out in financial terms, you probably can. However, if you are on NEM and don't put a significant value on the backup power, it still may not pencil out.

Personally, I had already budgeted for a nat-gas backup generator and I got a huge SGIP rebate. With those things along with the federal tax credit taken out of the up-front cost, I can actually say that I will eventually come out ahead financially by having the Powerwalls.

 

[jrweiss98020]

A single Powerwall may never give you the return you want, because it will not likely power the house long enough. IF you can work it so you no longer have to buy peak-rate electricity, you may actually get a positive return. Depending on your use, you may need 3 or more Powerwalls.

 

[h2ofun]

Boy, do I have a bunch of questions about adding a Powerwall to my existing Tesla Solar Panel system! I placed my deposit and have started the preliminary process. We charge at primarily home for my wife's Tesla M3LR, we like the idea of having backup charging in case of a power interruption.
#1) Is the financial outlay worth it?

One of many questions.....

IMO, a Powerwall will never pay for the cost. But if one has money to burn, and likes techno stuff, ....

 

[OldPro]

I don't have money to burn and I get bored with techno stuff. I will be taking a hard look at if adding a Powerwall pencils out

 

[nicholb]

Unless you have time of use metering and need to time shift usage, Powerwall may not come out as a positive in pure spreadsheet numbers.

The main advantage of Powerwalls is in the grid down situation. Beyond the obvious being to run on batteries you will also be able to run your solar generation during grid down. Normally solar also needs to shut down when there is no grid but with batteries there is now a place for excess electricity to go so your solar can continue generating.

As for charging your car off Powerwalls, the car's battery is bigger than the Powerwall. What you will be able to do is charge the car during the day from solar when the grid is down.

The number of Powerwalls you need depend on your loads. You have to look at both peak load and the amount of kwh you use a day. From that you can figure out how many you need to give you the amount of backup time you want.

 

[hmcgregoraz]

IMHO when trying to look at $ with PowerWalls, the only way the $ work out is if you include a potential whole house generator backup, as that is the most comparable solution.

The powerwall gateway is akin to an automatic transfer switch for a house generator.

The energy storage is akin to having a small amount of LP gas on site to run the generator (and is more independent than natural gas would be). Your solar is like a near daily top off of your LP gas.

We went with 3x powerwalls in our system, and one of the primary reasons is that my mom lives with us, and is not able to transport well if we lost cooling (and loss of cooling in Arizona is a big deal), so we were either looking at generator options to keep cooling, or powerwalls.

If you try and just look at the grid cost offset with powerwalls the $ won't work out, as the grid, even the more expensive parts of it, is just too cheap.

-Harry

 

[OldPro]

Put down my $100 reservation for a Powerall to add to my Tesla Solar Panels. Inspection completed this morning, very detailed visit. Waiting to hear back on a plan. Tech says no more interior installation in the garage. Interesting to see what the price for install will be. Still penciling out the investment. No incentives for 92131 other than Federal Tax Credit and $500 Tesla rebate for installs by 10/31. I was hoping for a bit more.

 

[mswlogo]

Charging your EV during a power outage is probably the last thing you’d use a Power Wall for.

 

[hmcgregoraz]

Charging your EV during a power outage is probably the last thing you’d use a Power Wall for.

Depends on "how" you are charging the EV.

We produce a lot of excess solar, even with our power walls, without charging our EVs.

Being able to charge EVs from Solar, during a power outage, is a benefit of having the powerwalls.

I would first get the power walls to over 80% charge, then I would start the EVs charging at a rate that is still charging the power walls slowly, but also putting excess solar into the EVs.

Basically without batteries and a transfer gateway, your solar is offline during an outage, with batteries and a gateway your solar is online, and that gives you EV charging options too.

 

[mswlogo]

I couldn’t even line up charging my EV in good weather from Solar. Never mind trying to do it in the middle of winter, which is when I most likely will lose power, with snow or ice on the panels and low output even if the panels were clear. I’d have to leave the car in a low state of charge before the storm. I prefer charge as much as I can before the storm.

You might get one lucky 1/4 of day charging per year. Where all the ducks lined up just perfect.

 

[K5TRX]

We produce a lot of excess solar, even with our power walls, without charging our EVs.
...
Basically without batteries and a transfer gateway, your solar is offline during an outage, with batteries and a gateway your solar is online, and that gives you EV charging options too.

That's exactly it! With even one Powerwall+, you can use your solar panels in a power outage. Powerwalls allowed you to charge the cars and the Powerwalls from solar in a power outage. Of course you balance your own needs. For us, charging the Powerwalls to 100% going into the evening is our top priority in an outage. You can use excess solar generation that would be sold to the grid to charge cars.

And in the winter months, Powerwalls are just as important. Here, ComEd allows Net Metering and Hourly Pricing. So on a snowy day you may get very little solar generation. But hourly pricing that lets us charge when our cost for power from ComEd is low, typically from midnight to 5 AM. Then use the power you stored at night during the day when power costs more.

There are nights ComEd pays consumers to take their power because they can't quickly shut down coal-fired and nuke plants. I would argue that for someone in a snowly, cloudy place, Powerwalls can make a lot of sense. Check with your utility about Time of Day (Hourly Pricing) and Net Metering.