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Full Home Backup or Partial?

ONEDVSMOFO

Member
Aug 31, 2018
120
65
CA
I’m received my quote from Tesla (medium size with 2 PWs) which they say would power the whole home.

For those with similar sized systems, did you guys go with full home or partial? I’m thinking partial just to save the $10000 and maybe down the road purchase a second one if needed.

My PGE application estimated I’d be -2,511 kWh short of my estimated yearly usage. Anyone know how accurate these estimates are? Do they tend to lean more one way than the other?
 

gpez

Member
Apr 25, 2019
735
602
USA
What is your home's daily kWh power consumption at the highest, average, and minimum (ie in an emergency)? Do you have any critical high wattage appliances? Some folks living in the south can't survive without AC :)

With no EV charging my home averages about 25kWh/day and in an outage we could comfortably use 12kWh/day, 6kWh is probably the absolute minimum for night lighting + fridge/freezer. We have an 8.55kw system and only 1 Powerwall purely for backup of critical loads only (no AC, oven, dryer, or L2 EV charger). That will give us a day or so by itself but I also have an EV wiring kit for my Volt and a pure sine inverter that can handle most of my important house loads for multi-day outages with no sun.

We don't have TOU charging where I live and my thinking is like yours that maybe down the road I'd consider a second (especially if they institute some peak rates). The tech is always improving and I imagine the PW3 will be a similar step up that the PW2 was over the original.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,802
12,519
Riverside Co. CA
I’m received my quote from Tesla (medium size with 2 PWs) which they say would power the whole home.

For those with similar sized systems, did you guys go with full home or partial? I’m thinking partial just to save the $10000 and maybe down the road purchase a second one if needed.

My PGE application estimated I’d be -2,511 kWh short of my estimated yearly usage. Anyone know how accurate these estimates are? Do they tend to lean more one way than the other?

when people get solar, they tend to start using more power. If you are already thinking you might want the 2nd powerwall, you should get it now.

The second powerwall is not an additional 10k, NOW. I know powerwall pricing (from tesla at least) very well because I am in process of purchasing 2 of them from tesla (in waiting for permit stage).

From tesla, powerwalls are:

1 powerwall

Powerwall = 6500
Install = 3000
Permits = 500
Gateway = 1100

=11,100
Taxes applicable to your state / county

The second powerwall adds 6500 for the powerwall and SUBTRACTS 500 from the installation, meaning the second powerwall is 6000 (not 10k) more. Again, pricing from tesla. Third party pricing is different and all over the map, without breaking everything out.

If I were in your shoes, I would ask for a re desgin (in fact I did, when I was getting solar in 2015 from tesla). they originally sized me for 80% of my yearly usage, and I made them upsize the system to 98% of my yearly usage. I didnt have an EV at the time but told them "I am getting one next year". I didnt end up getting it the next year, but 3 years later. Anyway.

I would go with whole home backup, and 2 powerwalls (whole home except for backing up the charging circuit for the EV). My plan on that is, if we have a multi day outage, I will just drive my car to a local supercharger. Makes no sense to me to charge my 75kW car with my soon to be 27kW of battery. If my car was about to be dead, I would just plug it in on 120 to get enough charge to get to a supercharger.

Anyway, I am planning on backing up everything except my EV circuit. I have 2 air conditioning units, and asked tesla to connect them on the backup side and was told "engineering signed off on that". When the electricians actually come, I will check in with them. I live inland so its hot during the summer, and it would be nice to be able to run the AC just briefly (30 minutes) to reduce heat if we were in a power outage.

Anyway, sorry for rambling on. I would have tesla resize that system to come much closer to my yearly usage, and I would get 2 powerwalls.. but I am not a fan of "I wish I would have gotten....." (the bigger TV, the faster car, the more powerful AV receiver, the larger Solar / powerwall). In my mind, its MUCH easier to not use some capacity you have, than add it later.... provided one has the finances to get the larger / more powerful thing.

If finances are an issue, then its better to have some solar and backup than none. My system is leased (unfortunately) because in 2015 I could not afford to buy it, but my calculations showed me even leased solar was going to save me $100 a month on electricity on average. I am going to buy it from tesla next year when I can, and am glad I jumped in when I did. Its just frustrating to have this solar on my home and still be without power in a power outage, which has happened to me and suuuckkkks... lol
 

electracity

Active Member
Jun 8, 2015
4,028
3,458
60606
Do you camp or otherwise spend time off grid? I find that some power is much, much better than no power. Although I use a lot of energy on a normal day, I have no need to fully power my house for a few days without mains electricity. I find that paying to fully power my house is an unnecessary extravagance as well as somewhat wimpy.

However, some people want to pay for complete normalcy in an outage. Figuring out you and your family's psychology on this issue will tell you what to buy.

But realize that the first people to die in the zombie apocalypse will be those who become uncomfortable without full electrical service :)
 
  • Funny
Reactions: jjrandorin

Oldschool496

Member
Sep 27, 2017
707
415
Florida
But realize that the first people to die in the zombie apocalypse will be those who become uncomfortable without full electrical service :)
It may be the other way around because at night your place will be lit like Christmas Tree and everyone will be coming to your place, in that ZOMBIE APOCALYPSE your describing.
 
  • Funny
Reactions: djlott

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,802
12,519
Riverside Co. CA
Do you camp or otherwise spend time off grid? I find that some power is much, much better than no power. Although I use a lot of energy on a normal day, I have no need to fully power my house for a few days without mains electricity. I find that paying to fully power my house is an unnecessary extravagance as well as somewhat wimpy.

However, some people want to pay for complete normalcy in an outage. Figuring out you and your family's psychology on this issue will tell you what to buy.

But realize that the first people to die in the zombie apocalypse will be those who become uncomfortable without full electrical service :)

Lol! Re: that upcoming zombie apocalypse... you are right, I want the ABILITY to have full normalcy, but I certainly would not run my home at full bore in an outage. For me, it would just mean I could go almost indefinitely during the summer, and for quite a few days in the winter. For example, I have an electric oven (40amp) that I want backed up. In an outage, If I wanted to bake, I would just use one of my BBQ grills (my pellet grill bakes very well, have done biscuits and cake out on that thing before).

In my mind, having more capacity means I can dial back and go longer in an outage....but yeah when the zombies come they will know which houses to go to by who still has the lights and TV on ;-)
 

Oldschool496

Member
Sep 27, 2017
707
415
Florida
In my mind, having more capacity means I can dial back and go longer in an outage....but yeah when the zombies come they will know which houses to go to by who still has the lights and TV on ;-)
Yes, I assume you few folks are experiencing blackouts. Here during some past hurricanes, you get the picture real quick, when the streets are black at night and there is one guy, he has his standby gen going. It kind of a red flag. I'm knocking on his door for a shower and a long extension cord.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,802
12,519
Riverside Co. CA
Yes, I assume you few folks are experiencing blackouts. Here during some past hurricanes, you get the picture real quick, when the streets are black at night and there is one guy, he has his standby gen going. It kind of a red flag. I'm knocking on his door for a shower and a long extension cord.

ROFL :
 

electracity

Active Member
Jun 8, 2015
4,028
3,458
60606
Yes, I assume you few folks are experiencing blackouts. Here during some past hurricanes, you get the picture real quick, when the streets are black at night and there is one guy, he has his standby gen going. It kind of a red flag. I'm knocking on his door for a shower and a long extension cord.

I have a neighbor who complained about another neighbor leaving their outside lights on during a blackout. She was without power and evidently felt the neighbor with the full house backup was being too showy.
 
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Reactions: Oldschool496

ajdelange

Active Member
Dec 10, 2018
1,077
638
Virginia/Quebec
The tough part of all this is that it is totally a statistical game. You don't know what is going to happen so you have to plan based on what you think might happen and what you are willing to live with. How often does the power go out in your region? How long does it typically stay out? What is your average power consumption? What is your median consumption? 90th %-ile consumption, etc.? Do you want to be covered if the power goes out for a week? Once you have all these data in hand you can calculate the size of a system you need.

The most fundamental calculation is based on your averge consumption and the capacity of your backup system. If average consumption is 1.3 kW and a powerwall has capacity of 13 KWh then it can run your house for, on average, 10 hours. But if your A/C draws 5 kW and is on with a duty cycle of 40% that raises consumption, during times when it is on then it alone will drain your powerwall in 6.5 hrs. Can you live with shedding the A/C if the power goes out?

Point is that there are many, many factors to consider and coming up with a system design isn't easy.
 
  • Informative
Reactions: jjrandorin

Uncle Paul

Well-Known Member
Nov 1, 2013
6,299
7,596
Canyon Lake,CA
Power out on a hot day, many would enjoy just being to run the AC enough to reduce the 100º muggy temps down to a much more comfortable 85º dryer interior. Just enough to take the edge off.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,802
12,519
Riverside Co. CA
Power out on a hot day, many would enjoy just being to run the AC enough to reduce the 100º muggy temps down to a much more comfortable 85º dryer interior. Just enough to take the edge off.
Thats where I am... and I am in your general location (Im on the border of Temecula and Murrieta, and I know exactly where canyon lake is).
 

jkoya

NA2 NSX
Nov 21, 2018
3,626
1,569
Northern CA
Yes, I assume you few folks are experiencing blackouts. Here during some past hurricanes, you get the picture real quick, when the streets are black at night and there is one guy, he has his standby gen going. It kind of a red flag. I'm knocking on his door for a shower and a long extension cord.

This reminds me of that episode of "The Twilight Zone" where only one house had power .......
 

GenSao

Member
Aug 3, 2017
569
967
Pleasant Hill, CA
when people get solar, they tend to start using more power. If you are already thinking you might want the 2nd powerwall, you should get it now.

The second powerwall is not an additional 10k, NOW. I know powerwall pricing (from tesla at least) very well because I am in process of purchasing 2 of them from tesla (in waiting for permit stage).

From tesla, powerwalls are:

1 powerwall

Powerwall = 6500
Install = 3000
Permits = 500
Gateway = 1100

=11,100
Taxes applicable to your state / county

The second powerwall adds 6500 for the powerwall and SUBTRACTS 500 from the installation, meaning the second powerwall is 6000 (not 10k) more. Again, pricing from tesla. Third party pricing is different and all over the map, without breaking everything out.

If I were in your shoes, I would ask for a re desgin (in fact I did, when I was getting solar in 2015 from tesla). they originally sized me for 80% of my yearly usage, and I made them upsize the system to 98% of my yearly usage. I didnt have an EV at the time but told them "I am getting one next year". I didnt end up getting it the next year, but 3 years later. Anyway.

I would go with whole home backup, and 2 powerwalls (whole home except for backing up the charging circuit for the EV). My plan on that is, if we have a multi day outage, I will just drive my car to a local supercharger. Makes no sense to me to charge my 75kW car with my soon to be 27kW of battery. If my car was about to be dead, I would just plug it in on 120 to get enough charge to get to a supercharger.

Anyway, I am planning on backing up everything except my EV circuit. I have 2 air conditioning units, and asked tesla to connect them on the backup side and was told "engineering signed off on that". When the electricians actually come, I will check in with them. I live inland so its hot during the summer, and it would be nice to be able to run the AC just briefly (30 minutes) to reduce heat if we were in a power outage.

Anyway, sorry for rambling on. I would have tesla resize that system to come much closer to my yearly usage, and I would get 2 powerwalls.. but I am not a fan of "I wish I would have gotten....." (the bigger TV, the faster car, the more powerful AV receiver, the larger Solar / powerwall). In my mind, its MUCH easier to not use some capacity you have, than add it later.... provided one has the finances to get the larger / more powerful thing.

If finances are an issue, then its better to have some solar and backup than none. My system is leased (unfortunately) because in 2015 I could not afford to buy it, but my calculations showed me even leased solar was going to save me $100 a month on electricity on average. I am going to buy it from tesla next year when I can, and am glad I jumped in when I did. Its just frustrating to have this solar on my home and still be without power in a power outage, which has happened to me and suuuckkkks... lol

I will echo @jjrandorin 's statement. I went with two Powerwalls for the piece of mind and the ability to use our AC during an outage. Do consider the following:

  • For TOU rate arbitage, you'll have more capacity to mitigate for peak use.
  • Batteries do degrade over time. Tesla batteries are warrantied to 70% after 10 year. Having 2X will give you 18.5 kWh (13.5 x 2 x 70%) of capacity at the 10 year mark.
  • In an extended power outage, save more solar power and mitigate for reduced solar production in the winter with a higher reserve.
  • Ability to use more powerful appliances 30A and up. Can even (efficiently) charge your EV at a higher rate.
  • Cost of Powerwalls have increased over time. Mine cost $5,500 when I installed and they are now $6,500. They are an apprciating asset... ^_- Cost to install an additional one later will be more than with you current install.
  • If getting 2X PW, do ask for more panels to meet 100% of your use. Solar panels will degrade in time. Going 100% will mitigate for this. In fact my usage has balooned since my initial 5.7 kW solar panel system install. I am having Tesla install a 3.8 kW
 
Last edited:

ONEDVSMOFO

Member
Aug 31, 2018
120
65
CA
I live in the central coast of CA. The longest outage we’ve had was about 6 hours. That was due to a car accident shearing a utility pole.

We’ve had a few outages, mostly when we first moved in and due to maintenance. None lasted more than a couple of hours.

I don’t know what PGE plans are for blackouts in our area. Most seem to be well north or south of us.

I sent an email requesting a system redesign. I’m looking for the screenshots I had earlier this year from a Tesla quote. I wanna say it met 122% of our annual usuage, 2 PW’s, and it was the same or just a few hundred more than my current quote.

I asked about the reduction in solar prices that was announced and the advisor fed me some line about how they’ve cut out home inspections prior to installs and do everything online so that saves them money, and they pass on the savings to me.
 
  • Informative
Reactions: jjrandorin

Sherlo

Member
Feb 13, 2019
348
398
SF Bay Area
when people get solar, they tend to start using more power. If you are already thinking you might want the 2nd powerwall, you should get it now.

If I were in your shoes, I would ask for a re desgin (in fact I did, when I was getting solar in 2015 from tesla). they originally sized me for 80% of my yearly usage, and I made them upsize the system to 98% of my yearly usage. I didnt have an EV at the time but told them "I am getting one next year". I didnt end up getting it the next year, but 3 years later. Anyway.

I would go with whole home backup, and 2 powerwalls (whole home except for backing up the charging circuit for the EV). My plan on that is, if we have a multi day outage, I will just drive my car to a local supercharger. l


Great advice, wish I had considered this 8 years ago.
 

Dan123

Member
Jun 19, 2018
451
322
Miami
I’m received my quote from Tesla (medium size with 2 PWs) which they say would power the whole home.

For those with similar sized systems, did you guys go with full home or partial? I’m thinking partial just to save the $10000 and maybe down the road purchase a second one if needed.

My PGE application estimated I’d be -2,511 kWh short of my estimated yearly usage. Anyone know how accurate these estimates are? Do they tend to lean more one way than the other?


The thing about partial backup is that you really don't save that much, because you are going to have an electricial install a separate panel, and reroute all of the backup loads to that separate panel. When it is all done, you will probably only save $3000-$4000 by doing a partial backup.
 

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