NorCal, Tesla 4kw + 1 powerwall

[solar_future]

It looks like PG&E / Bay Area electricity has a lot of options / complications (e.g., time-of-use, tiers), so mervinj7's experience might be helpful to navigate the different electricity rates and net-energy-metering credits (e.g., Silicon Valley Clean Energy CCA). But here's an outsider guess looking at EV2-A (single meter) rate assuming NEM credits at retail:

https://www.pge.com/en_US/residential/r ... -plan.page

17¢/kWh from 12am - 3pm Off-Peak
37¢/kWh from 3pm - 4pm Part-Peak
48¢/kWh from 4pm - 9pm Peak
37¢/kWh from 9pm - 12am Part-Peak

As from VaR's production and consumption image of May 8th, production drops off around 5pm just after electricity jumps up to 48¢/kWh, and the higher rate also matches electricity usage going up in the evening when people return home. If we blend Part-Peak/Peak rates to be 43¢/kWh from 3pm - 12am, a 4kW system could produce up to 30kWh in the summer time with roughly 20kWh in 8 hours at Off-Peak 17¢/kWh for $3.40 and 10kWh in 4 hours at Peak-ish 43¢/kWh for $4.30. If we say your electricity usage is 10kWh Off-Peak $1.70 and 20kWh Peak-ish $8.60, this is a $10.30 daily cost that is reduced to $2.60, i.e., $7.70 savings generated by solar. Tesla's $7400 / $7.70/day = 2.6 years assuming this ideal summer day.

A battery pack allows you to shift your Peak electricity usage to look like Off-Peak, so charging 10kWh battery during Off-Peak and using that during Peak-ish makes the usage more match the 4kW solar production, so 20kWh Off-Peak $3.40 and 10kWh Peak-ish $3.40 results in an additional $2.60 saving for a $0 electricity charges -- i.e., $10.30 savings generated by solar + battery. Tesla's ($7400 + $6290) / $10.30/day = 3.6 years.

The breakeven time for solar is shorter than solar + batteries, but batteries do provide non-trivial ROI (about 1/3 of solar in this example) and also provide additional benefits such as protection from outages.

Also, an EV purchase in a couple years might have better vehicle-to-grid functionality which basically transforms the car into a mobile battery backup with much larger capacity (1 Model Y is more than 5 powerwalls). But that also has trade-offs of driving the car vs acting as a backup.

another way of looking at is that the marginal payoff period of the battery is 6.6 years ($6290/$2.6/365). Plus with a battery you have power when the power goes out.

[Ampster]

..............

Also, an EV purchase in a couple years might have better vehicle-to-grid functionality which basically transforms the car into a mobile battery backup with much larger capacity (1 Model Y is more than 5 powerwalls). But that also has trade-offs of driving the car vs acting as a backup.

Whether vehicle to grid functionality ever comes about, an EV can allow you to leverage Time of Use rates. It is the classic load shifting scenario because you can plug in your car anytime and the timer turns on the charger whenever you program it. I have consumed more than I produced in the past several years and still only paid the fixed charges. In the summer for every kWh that I sent to the grid I could draw down 3 kWhs at off peak rates.

[Wannaretireearly]

It looks like PG&E / Bay Area electricity has a lot of options / complications (e.g., time-of-use, tiers), so mervinj7's experience might be helpful to navigate the different electricity rates and net-energy-metering credits (e.g., Silicon Valley Clean Energy CCA). But here's an outsider guess looking at EV2-A (single meter) rate assuming NEM credits at retail:

https://www.pge.com/en_US/residential/r ... -plan.page

17¢/kWh from 12am - 3pm Off-Peak
37¢/kWh from 3pm - 4pm Part-Peak
48¢/kWh from 4pm - 9pm Peak
37¢/kWh from 9pm - 12am Part-Peak

As from VaR's production and consumption image of May 8th, production drops off around 5pm just after electricity jumps up to 48¢/kWh, and the higher rate also matches electricity usage going up in the evening when people return home. If we blend Part-Peak/Peak rates to be 43¢/kWh from 3pm - 12am, a 4kW system could produce up to 30kWh in the summer time with roughly 20kWh in 8 hours at Off-Peak 17¢/kWh for $3.40 and 10kWh in 4 hours at Peak-ish 43¢/kWh for $4.30. If we say your electricity usage is 10kWh Off-Peak $1.70 and 20kWh Peak-ish $8.60, this is a $10.30 daily cost that is reduced to $2.60, i.e., $7.70 savings generated by solar. Tesla's $7400 / $7.70/day = 2.6 years assuming this ideal summer day.

A battery pack allows you to shift your Peak electricity usage to look like Off-Peak, so charging 10kWh battery during Off-Peak and using that during Peak-ish makes the usage more match the 4kW solar production, so 20kWh Off-Peak $3.40 and 10kWh Peak-ish $3.40 results in an additional $2.60 saving for a $0 electricity charges -- i.e., $10.30 savings generated by solar + battery. Tesla's ($7400 + $6290) / $10.30/day = 3.6 years.

The breakeven time for solar is shorter than solar + batteries, but batteries do provide non-trivial ROI (about 1/3 of solar in this example) and also provide additional benefits such as protection from outages.

Also, an EV purchase in a couple years might have better vehicle-to-grid functionality which basically transforms the car into a mobile battery backup with much larger capacity (1 Model Y is more than 5 powerwalls). But that also has trade-offs of driving the car vs acting as a backup.

[Wannaretireearly]

I don't understand with your monthly electric bills that low how you plan to get a decent ROI? Are your e-bills expected to go up significantly in the near future? I had trouble rationalizing an $11K cash purchase on my very simple 6.6 kW grid-tie system and it had an estimated payback of 7 years. Depending on the estimates you shared you are between maybe 10-15 years payback? People move to a new home on average every 7 years right?

Good question. Yep. Without the fed rebate I am looking at a 10-12 year payback.

I'm banking on getting the 26% fed rebate next year which brings my total cost to around 13-14k (10k + 6k + 2k tax = 18k. 18k - 4k fed discount = $14k cost to me).

I think I'm down to 8 year ROI factoring Fed rebate.

Now, if I actually factor pge net metering and the $ benefit I get from using the powerwall during peak times, the roi looks better. I'll post a calc in another post that someone did for me on another forum...

[azdave]

According to multiple studies and common sense....

What does common sense have to do with it? I think you've been drinking the solar salesman Kool-aid.

Around here, few home appraisers give any value to having solar, even if the panels are owned free and clear. Solar on the home is often a bargaining chip for the buyer to get seller concessions because there is often a lease transfer involved.

[SunEagle]

According to multiple studies and common sense, homes with solar power systems sell for more than those without, so if you move, you will recoup some of your money in a higher resale price.

Actually that is not correct for all homes with solar. It may be very attractive to purchase a home with an existing solar system in some areas of some states but I can tell you an existing solar pv system is a liability in a lot of homes in Florida. For that matter solar isn't even mentioned in a selling description while a pool is.

[solar_future]

I don't understand with your monthly electric bills that low how you plan to get a decent ROI? Are your e-bills expected to go up significantly in the near future? I had trouble rationalizing an $11K cash purchase on my very simple 6.6 kW grid-tie system and it had an estimated payback of 7 years. Depending on the estimates you shared you are between maybe 10-15 years payback? People move to a new home on average every 7 years right?

According to multiple studies and common sense, homes with solar power systems sell for more than those without, so if you move, you will recoup some of your money in a higher resale price.

[azdave]

...PGE electric bill runs 100 to 130...

...cost effectiveness/roi is an important factor to me.

I don't understand with your monthly electric bills that low how you plan to get a decent ROI? Are your e-bills expected to go up significantly in the near future? I had trouble rationalizing an $11K cash purchase on my very simple 6.6 kW grid-tie system and it had an estimated payback of 7 years. Depending on the estimates you shared you are between maybe 10-15 years payback? People move to a new home on average every 7 years right?

[Wannaretireearly]

Thanks scrambler. We have gas tankless heater, and a gas stove. In the event of an outage, we would avoid running dryers, ac etc. Were not heavy ac users any case. Appreciate your response

[scrambler]

The Powerwall is limited to 5kW sustained, so If you have a single Powerwall, and unless you do not have any heavy power users (AC, Electric Oven, Electric Water heater, Dryer, Electric car...) the installation will most likely include moving all the light loads (15-20 amps breakers) to a critical load panel, and these will be the only one powered during an outage (which is usually fine)

[Wannaretireearly]

I would suggest going on to teslamotorsclub.com
There you will find more users with experience using Tesla systems. The Tesla Energy sub forum has a lot of activity. There are users there with specific PGE experience that can help you pick the best rate plan. You may also be part of a CCA (Community Choice Aggregation) plan that offers incentives. I am part of Sonoma Clean Power and receive $5 a month to let them control my EV charging when the grid is stressed. Long term Tesla has plans to roll out a plan to aggregate Powerwalls so you could get paid for charging your Powerwall.
They are already doing this in Vermont.

Great info. Thank you!!

[Ampster]

One of the reasons I wanted to post here first, before committing to Tesla..

I would suggest going on to teslamotorsclub.com
There you will find more users with experience using Tesla systems. The Tesla Energy sub forum has a lot of activity. There are users there with specific PGE experience that can help you pick the best rate plan. You may also be part of a CCA (Community Choice Aggregation) plan that offers incentives. I am part of Sonoma Clean Power and receive $5 a month to let them control my EV charging when the grid is stressed. Long term Tesla has plans to roll out a plan to aggregate Powerwalls so you could get paid for charging your Powerwall.
They are already doing this in Vermont.

[Wannaretireearly]

Reads like you've pretty well sold yourself on Tesla.

Good luck.

It does, yes. One of the reasons I wanted to post here first, before committing to Tesla..

[J.P.M.]

Reads like you've pretty well sold yourself on Tesla.

Good luck.

[Wannaretireearly]

Are you subject to PGE public safety power shutdowns?
Did Tesla look at your power bills?
Are you getting any rebates?
One question for Tesla is whether the Powerwall can cover your whole house or will you need a separate critical loads panel.

We just missed out on the power shutdowns last year. Tesla is looking at my bills at the mo.
I dont get any rebates currently.
Not sure if I need a critical loads panel, haven't been told yet. I've just uploaded all the pics per step 2 of the tesla process...