Need help understanding powerwall benefits

[Hawkhandler]

I need some help making sense of all this. The information here is specific to Northern California so I apologize for the specific nature of the questions. I currently have a small solar array from Tesla on the subscription plan and I am on the PG&E EV2-A rate plan with an electric vehicle that we are charging during off-peak hours. I'm trying to figure out 2 things:

1) Should i get moved to the EVB plan? Per the iphone app: PG&E Toolkit it looks like i would be doing significantly better if we were on this plan. We'll need PG&E to install a separate meter for the car? do they charge us for that?
2) Per this app, it also looks like we'd be doing way better if we had a powerwall. I don't understand how that works? how will that save us money? Do we set it so that we are using the power stored in the powerwall during peak hours? I'd love to think that someone at Tesla could help me understand this but given my experience I highly doubt it.

I just want a way to make sense of all this and know how to estimate what the savings would be on the other plan and/or with a powerwall AND less state and federal incentives.

Thanks a lot in advance for any guidance you can provide.

 

[aesculus]

PG&E will charge you for the second meter and you also have to have the panel/circuit installed. The estimates can range from $300 to $1000 for this depending on your situation and contractors etc.

And theoretically you can only charge your car on it too so you better be driving a lot. Your regular house consumption would have to be on another plan that will probably be more expensive, especially if you have time shift loads (like when you wash clothes, dishes etc).

I cannot fathom how you would benefit from a PW with a small amount of solar in Oakland. The bigger returns are for folks with larger solar arrays in more solar rich areas. Also people who use a fair amount of peak energy (think cooling) that they can time shift off peak with the PWs.

And then the big one: Avoiding PG&E's PSPS.

Also is EV-B still available? EV-A is not.

 

[miimura]

EV-B is still available if you have a second PG&E meter installed and only EVSE are connected to that meter. I would guess that between the electrician charges and PG&E charges, it would cost between $1,000 and $2,500 to get separate metering set up, depending on the details of your service connection and main panel configuration.

I was previously on EV-A until I was kicked out to EV2-A. On either plan, I estimate that my small solar system and two Powerwalls save met about $700 per year by time shifting my generation and avoiding paying for Peak period usage. It also maximizes export of what little solar generation I have during Peak hours. If you have more Winter generation or more Summer Peak consumption than me, you could save a lot more money than I do.

This is a typical intraday chart from yesterday that shows what the Powerwall is doing to time shift my generation. The green area below the baseline is Powerwall charging and above the line is discharging. The gray area below the line is export to the grid.

 

[Hawkhandler]

EV-B is still available if you have a second PG&E meter installed and only EVSE are connected to that meter. I would guess that between the electrician charges and PG&E charges, it would cost between $1,000 and $2,500 to get separate metering set up, depending on the details of your service connection and main panel configuration.

I was previously on EV-A until I was kicked out to EV2-A. On either plan, I estimate that my small solar system and two Powerwalls save met about $700 per year by time shifting my generation and avoiding paying for Peak period usage. It also maximizes export of what little solar generation I have during Peak hours. If you have more Winter generation or more Summer Peak consumption than me, you could save a lot more money than I do.

This is a typical intraday chart from yesterday that shows what the Powerwall is doing to time shift my generation. The green area below the baseline is Powerwall charging and above the line is discharging. The gray area below the line is export to the grid.

View attachment 552765

thanks. this is helpful. I didn't realize that the rest of the house has to be on a separate plan than EVB so that doesn't make any sense. And a powerwall on EV2A with our current usage/production doesn't make a ton of sense either. $500/year of savings takes way too long for the powerwall to pay for itself. Thanks for helping.

 

[jjrandorin]

Whether it makes sense depends on how you decide to designate the value, though. The $500 a year savings may not make financial sense to you (and I get that) but if you are in the least bit in chance of being impacted by the Power Safety Shutoffs (PSPS) from the various utilities, the psychology of knowing "you will have power" can be tremendous, for many.

So, you need to define your value proposition on it. Is it strickly financial payback, or is it for having backup power, or is it ensuring that you will have emergency power in the case of an outage in your neighborhood so that you dont lose your food in fridge, and can work if you work from home sometimes or all the time?

Speaking only for myself, i have had solar since 2015, but adding the powerwalls in january of this year has given me an immense sense of well being at home... Especially given the "shelter in place" situation with covid 19, knowing for 100% fact that I have power there, and will have power there to basically live as normal, pretty much no matter what, as long as the sun is up every couple of days makes my home feel more like a "sanctuary" even though I liked it before.

hard to quantify all that, and not everyone will feel that way. I didnt know that the powerwalls were going to give me that sense of attachment. I just figured they were backup power... but watching the elctrons flow in the app, etc... doing "off grid" tests and seeing what happens, and how I can live basically with my regular lifestyle, even if no grid...

To quote a mastercard commercial "priceless" at least for me.

 

[Hawkhandler]

Whether it makes sense depends on how you decide to designate the value, though. The $500 a year savings may not make financial sense to you (and I get that) but if you are in the least bit in chance of being impacted by the Power Safety Shutoffs (PSPS) from the various utilities, the psychology of knowing "you will have power" can be tremendous, for many.

So, you need to define your value proposition on it. Is it strickly financial payback, or is it for having backup power, or is it ensuring that you will have emergency power in the case of an outage in your neighborhood so that you dont lose your food in fridge, and can work if you work from home sometimes or all the time?

Speaking only for myself, i have had solar since 2015, but adding the powerwalls in january of this year has given me an immense sense of well being at home... Especially given the "shelter in place" situation with covid 19, knowing for 100% fact that I have power there, and will have power there to basically live as normal, pretty much no matter what, as long as the sun is up every couple of days makes my home feel more like a "sanctuary" even though I liked it before.

hard to quantify all that, and not everyone will feel that way. I didnt know that the powerwalls were going to give me that sense of attachment. I just figured they were backup power... but watching the elctrons flow in the app, etc... doing "off grid" tests and seeing what happens, and how I can live basically with my regular lifestyle, even if no grid...

To quote a mastercard commercial "priceless" at least for me.

right, that makes sense. where we are we have never had PSPS being in the middle of downtown Oakland. They do up in the hills but not down here.

 

[Takayama Todd]

Trying to make sense of ones powerwall/solar combination is not easy, but was made easier by reading these posts. My bet, the rate plan has the largest single impact when it comes to savings or payment at yearly true-up. My thinking and approach are based upon where my greatest opportunity for savings are e.g. the difference between the highest and lowest points. The EV2-A rate schedule and difference between baseline $ and peak $$$ allowed for the greatest potential of savings. The other rate plans e.g. TOU where too compacted regarding the base ($) to peak ($$) differential and didn't realize higher savings for me with a powerwall/solar combination. Your app settings and understanding the behavior of the powerwall settings comes with trial and error e.g. balanced vs cost savings, reserve settings, and setting ones price schedule for peak, partial peak and off-peak are important. Understanding the behavior is where it becomes interesting. I completely agree with, "price less", the peace of mind and the benefits of having a secondary source when the power goes out. The fact that my neighbors remind me every time they see my lights on when theirs are dark.

 

[swedge]

Hawk,

We just installed a single PowerWall, a nice addition to our 3.8kW solar which supplies about 85% of our annual electricity needs.

Almost the entire PowerWall cost is being covered by SGIP under their new "Equity Resiliency" incentive budget, which amounts to $13,200 per PowerWall. We qualified because we are on Medical Baseline, and our home is in a "Tier 2" fire hazard zone. If you can qualify, it makes the PowerWall pretty easy to justify.

For us the main benefit is having power during PG&E outages. I have done detailed estimates of the costs of various rate plans based on a full calendar year of solar production and our consumption data, hour by hour. SGIP rquires us to change from E1 to EV2, and this will actually increase our annual cost a bit, by $60 or so per year, because EV2 does not give any benefit for the medical baseline. If we do get eventually get an electric vehicle, the EV2 rate will be a big money saver over E1, especially with the PowerWall to shift all our house power use to off-peak hours.

I hope this information helps you.

SW