Will a Tesla powerwall work for me?

[jbrowdy]

I am a long time Tesla driver. I've been living over in the MS and MX forums, but this is my first time here! I have questions about Tesla energy, and I apologize in advance - I am a total rookie on this. Please feel free to shove me in the direction of some useful resource. Meanwhile, can I ask a few general questions:

• Is the Powerwall a good value compared with whatever else is out there (Generac, etc)
• I have an interest in using the Powerwall primarily as a source of backup energy in case of outages
  • is this foolish and/or overkill?
• Does anyone here charge their Powerwill solely with the grid with this purpose in mind?
  • I am getting the sense from local solar companies that I do not have an ideal property for solar. I believe I could put up enough panels to charge a Powerwall, but I would not have enough solar power to significantly offset my power bills. So, I am thinking of a small solar array with 1-2 Powerwalls as a option for backup power
    • The other option is a natural gas generator. They are loud, expensive and need a huge chunk of my lawn to function. I am still trying to compare cost of a small solar array coupled with Powerwalls against a generator (equipment, electrical work, etc)
• Does the Powerwall have software that allows you to interact with how power is allocated (ie, in an outage, can you prioritize HVAC over TV, etc)?
• f I can't do solar, does the Powerwall still make sense?

Again, sorry for the naïveté and general laziness in not finding these answers elsewhere (that said, I have been looking around)!

 

[jjrandorin]

(moderator note: post split off to its own thread from the powerwall+ thread as these are pre purchase questions)

================================

Hi,

Ill take a quick stab at some of your questions, maybe others have some other input.

• "Value" is relative. A battery solution will normally be more expensive than a generator solution, either a "little" more or a "lot" more depending on how you value adding solar or not with it or what you consider as being an appropriate amount of backup.
• Powerwall just as backup for outages (especially with no solar) is a pretty expensive proposition. Any battery solution fits into this "pretty expensive" proposition. When charged from solar, one can have their own microgrid. When charged from the grid, you have no way to refill it without the grid. I personally would not do any batteries without solar (powerwall or otherwise) unless they were free like some in CA have gotten.
• A few here charge from the grid for backup, but as far as I know, those who do that (charge from the grid with no solar) received their powerwalls through state grant programs (so in effect "free". "Free" is cheaper than a generator.
• The way loads are allocated during an outage is not through the software, its through the physical connection to the backup loads side or not.
• In my personal opinion, no, the powerwall (nor any battery system) makes sense to purchase without solar attached, unless its "free".

Batteries can make sense from a backup situation when you have enough solar, but even then a generator is still cheaper, in general. Value can mean many things to many people, so there can be value in things even though they are not cheaper. I find tons of value in my solar + powerwalls, and never considered a generator, even though I knew it would likely be cheaper. I wasnt interested in the noise, or having to go get fuel for it, etc, and already had solar. If I was in your situation I would likely look harder at a generator, OR explore how to get more solar.

To me, it doesnt make sense to buy powerwalls (or other batteries) for retail pricing with no solar (and you wont be able to get that directly from tesla, anyway, so will pay for a third party to do it for you.

 

[Southpasfan]

If your proposed Solar is "not enough", not sure what that means, but I think your analysis would be as follows

1. Solar itself can be converted from "cost" to "cost per kwh" relatively easily. You just have to get an estimate of what the system will produce, taking into account where you are located and shading, roof angle, etc., and then (a) convert the cost to a cost per month (or year) over 20 years, and (b) figure out kwh by month, or year, then divided (a) by (b). Note that others adopt the "convert the cost into years to pay-off" conversion. I don't find that helpful since you have to convert the cost to something but YMMV. Plenty of smart people like the years to pay off conversion.

2. My set up in SoCal is at around 10cents per kwh. If I had shading or was in a less sunny locale, it might be, say 15 cents per kwh.

3. Compare the number in Point 2 to what you are paying now. Since CA energy rates go from 23 cents per kwh up to 59 cents per kwh, you can see why many people hit the "order" button at this point. At this stage, regardless of how much the production is, if the cost per kwh is less than the grid is charging you nothing wrong with throwing some panels up there.

4. As to PWs, you might not even be able to charge them without solar, but, continuing the analysis, even a small solar system may produce more than is used at the time (i.e., produce 10kw at noon as opposed to the house using 5kw), and that extra can go into the PWs, which then means the PWs are available for back up.

5. As jjrandorian said, PWs just for "some back up" is a pretty expensive way to get back up. If all we are talking about is a situation where the grid goes down for an hour or two here or an hour or two there on bad afternoons, whether or not to get PWs to cover that is sort of based on "how bad do you want to avoid those otherwise non-serious but annoying outages?"

6. You mentioned you have a Tesla car. Keep in mind the battery pack in a Model 3 is the equivalent to six PWs. You are not going to be able to charge the PWs and the car with any sort of small system.

So, depending on your math, even a small solar system could be wise. Even with a small system, PWs can be cool to the extent they eliminate short outages, but otherwise are a luxury buy. Finally, to really get around the grid, as you can see discussed in other threads, you need a system that produces at least all, and ideally more, than your average usage.

I find it interesting that the solar companies don't even think you could make a significant dent in annual usage. Perhaps that is because of EV charging. Or maybe really bad roof orientation, or shading, or something.

 

[cali8484]

I am a long time Tesla driver. I've been living over in the MS and MX forums, but this is my first time here! I have questions about Tesla energy, and I apologize in advance - I am a total rookie on this. Please feel free to shove me in the direction of some useful resource. Meanwhile, can I ask a few general questions:

• Is the Powerwall a good value compared with whatever else is out there (Generac, etc)
• I have an interest in using the Powerwall primarily as a source of backup energy in case of outages
  • is this foolish and/or overkill?
• Does anyone here charge their Powerwill solely with the grid with this purpose in mind?
  • I am getting the sense from local solar companies that I do not have an ideal property for solar. I believe I could put up enough panels to charge a Powerwall, but I would not have enough solar power to significantly offset my power bills. So, I am thinking of a small solar array with 1-2 Powerwalls as a option for backup power
    • The other option is a natural gas generator. They are loud, expensive and need a huge chunk of my lawn to function. I am still trying to compare cost of a small solar array coupled with Powerwalls against a generator (equipment, electrical work, etc)
• Does the Powerwall have software that allows you to interact with how power is allocated (ie, in an outage, can you prioritize HVAC over TV, etc)?
• f I can't do solar, does the Powerwall still make sense?

Again, sorry for the naïveté and general laziness in not finding these answers elsewhere (that said, I have been looking around)!

Given your desire to run HVAC and charge EV, the required Powerwalls (Tesla recommends 3 to run central A/C) or other home battery systems are likely much more expensive than a natural gas generator. If financial justification is important to you then home battery systems are probably not a good fit.

 

[arnolddeleon]

You've received some good advice already, let me add a few more thoughts.

A scenario where a paying for battery only configuration for backup *might* make sense is if you have time of use metering of some kind, the rates between peak and off peak are sufficiently far apart, you are permitted by the utility/local regulations to perform power arbitrage *and* Tesla has a configuration that supports it. I don't recall if anyone has successful done this.

In general, a kWh of capacity in a Powerwall is cheaper than the competition.

There are energy management capable load centers (e.g. Span) but they're not cheap either. I've come to the conclusion that you either want it super cheap, in which case you go with manually controlling it yourself by turning off devices, or you want "care free" in which case you are usually just better off spending the extra money on more capacity (storage and/or generation) instead of trying to be clever with automated load management.

Batteries only make sense for any extended outage situation if you have a way of filling them (solar or some kind of generator). Theoretically this be done but I don't know if Tesla has released support for charging from a generator while the grid is down. A quick search didn't yield clear results. The reason to do this is if you wanted "quiet hours" so you run a generator for burst to power loads and charge up the Powerwalls.

 

[Lloyd]

Batteries only make sense for any extended outage situation if you have a way of filling them (solar or some kind of generator). Theoretically this be done but I don't know if Tesla has released support for charging from a generator while the grid is down. A quick search didn't yield clear results. The reason to do this is if you wanted "quiet hours" so you run a generator for burst to power loads and charge up the Powerwalls.

 

[Lloyd]

You are able to charge the batteries from a generator in an "off grid" installation.

 

[h2ofun]

You are able to charge the batteries from a generator in an "off grid" installation.

News to me.

 

[jjrandorin]

News to me.

Thats been said a few times before... but "off grid" in that instance means NO connection to a utility grid AT ALL, not just "throw the main breaker". "off grid" as in "my home doesnt have any connection at all to the utility, I either never had a meter, connection, or I told them to come take it off my property".

In that specific case, a generator can be configured to act as "the grid" for powerwalls, according to a few here. If one has a connection to a utility at all, meaning a meter on your property and an account with a utility, it can not be setup this way, whether you throw your main breaker or not.

 

[h2ofun]

Thats been said a few times before... but "off grid" in that instance means NO connection to a utility grid AT ALL, not just "throw the main breaker". "off grid" as in "my home doesnt have any connection at all to the utility, I either never had a meter, connection, or I told them to come take it off my property".

In that specific case, a generator can be configured to act as "the grid" for powerwalls, according to a few here. If one has a connection to a utility at all, meaning a meter on your property and an account with a utility, it can not be setup this way, whether you throw your main breaker or not.

Unless someone defines what off grid means, I am not assuming it really is off grid.

But with said, would love to see someone give pictures, drawings, etc that show an "off grid" where the batteries are charge from the generator.
Since I have panels, batteries, generator, I see not reason I would ever want to run my generator to charge batteries. Seems would be a waste of energy, and noisy to listen to, but maybe I am missing something.

 

[jjrandorin]

Unless someone defines what off grid means, I am not assuming it really is off grid.

But with said, would love to see someone give pictures, drawings, etc that show an "off grid" where the batteries are charge from the generator.
Since I have panels, batteries, generator, I see not reason I would ever want to run my generator to charge batteries. Seems would be a waste of energy, and noisy to listen to, but maybe I am missing something.

You dont have to assume, you just have to know what a specific individual is focused on based on their past posting. For example, I know you are focused on the fact that you can not charge from the grid during the winter, and it upsets you.

I know that @Lloyd is trying to get an off grid installation as in no connection to the utility due to past posts on the subject, so mentions of "off grid" mean no connection to the utility when said by that person.

You have actually participated in threads where @Lloyd has said this clearly, including that they have an off grid planning guide, like in this thread here:

Thoughts on additional power walls

Never said free I mean, you did: Had my generator a year and zero cost to maintain so far. But then you say it hasn't been zero cost since you've been running biweekly maintenance cycles, which consume fuel. $250/year is not 0 was only my point. Generators need to run maintenance cycles...

teslamotorsclub.com

My intent is to be off grid.

Yes, I have an off grid planning and installation guide I found online. It is marked with an NDA so I can't post it here.

(note that these above responses were specifically as responses to questions you asked about an off grid installation)

Additionally, @Vines has said, in these forums, that its possible to use the grid as a generator in an off grid installation:

Also just to be clear, the Generator and Powerwall will play nice together, but the functionality of charging the batteries during a grid outage is missing.

You can currently run an off grid home and charge the batteries just fine though I doubt many do so.

So, no guessing needed as to what "off grid" means, in this context.

 

[RKCRLR]

Unless someone defines what off grid means, I am not assuming it really is off grid.

But with said, would love to see someone give pictures, drawings, etc that show an "off grid" where the batteries are charge from the generator.
Since I have panels, batteries, generator, I see not reason I would ever want to run my generator to charge batteries. Seems would be a waste of energy, and noisy to listen to, but maybe I am missing something.

Enphase has an option to integrate a generator with their PV and battery storage:

https://support.enphase.com/s/article/Generator-with-Enphase-storage

The main advantage I see is to be able to recharge the storage during the day when PV isn't putting out enough so you can sleep without the noise at night.

 

[Vines]

Unless someone defines what off grid means, I am not assuming it really is off grid.

But with said, would love to see someone give pictures, drawings, etc that show an "off grid" where the batteries are charge from the generator.
Since I have panels, batteries, generator, I see not reason I would ever want to run my generator to charge batteries. Seems would be a waste of energy, and noisy to listen to, but maybe I am missing something.

If you connect a generator where the grid usually is, then the Powerwall 2 AC system is able to work together with the generator and charge the batteries or utilize house loads.

This requires NO UTILITY GRID present, for multiple reasons that arent obvious to a lay person.

 

[Vines]

Enphase has an option to integrate a generator with their PV and battery storage:

https://support.enphase.com/s/article/Generator-with-Enphase-storage

The main advantage I see is to be able to recharge the storage during the day when PV isn't putting out enough so you can sleep without the noise at night.

Both Generac and Enphase products can both recharge the batteries with a generator (Edit) while on Grid. As pointed out above, this is a requirement for many homes to last a winter outage, since the sun may be so low or overcast that there is no PV charge for days.

 

[h2ofun]

Enphase has an option to integrate a generator with their PV and battery storage:

https://support.enphase.com/s/article/Generator-with-Enphase-storage

The main advantage I see is to be able to recharge the storage during the day when PV isn't putting out enough so you can sleep without the noise at night.

I still do not get why anyone would do that! Before I had batteries, I had power outages, had solar and my generator. No way did I run the generator 24/7. Too costly, noisy, and not needed. I ran some in morning, lunch, and dinner time. Was plenty to get the refrig cold for the next day.

 

[RKCRLR]

Both Generac and Enphase products can both recharge the batteries with a generator (Edit) while on Grid. As pointed out above, this is a requirement for many homes to last a winter outage, since the sun may be so low or overcast that there is no PV charge for days.

Or the panels are covered with snow....

 

[cali8484]

If you connect a generator where the grid usually is, then the Powerwall 2 AC system is able to work together with the generator and charge the batteries or utilize house loads.

This requires NO UTILITY GRID present, for multiple reasons that arent obvious to a lay person.

This maybe technically true but is it supported by Tesla? In such scenario,what stops the PV inverters from backfeeding to generator if the batteries are full?

 

[h2ofun]

Both Generac and Enphase products can both recharge the batteries with a generator (Edit) while on Grid. As pointed out above, this is a requirement for many homes to last a winter outage, since the sun may be so low or overcast that there is no PV charge for days.

As I just posted, makes no sense to me, and I have done quite well surviving power outages in winter with my generator only running a few hours a day. Kept refrig plenty cold.

This for me all goes back to cost. For some, with plenty of money, great, they can guy whatever they want. But for the normal person, IMO, generator is the best solution, which is why I bought mine over batteries when I had a choice. But batteries are sexy. A tesla is sexy. Great, I am just practical and frugal.

 

[RKCRLR]

I still do not get why anyone would do that! Before I had batteries, I had power outages, had solar and my generator. No way did I run the generator 24/7. Too costly, noisy, and not needed. I ran some in morning, lunch, and dinner time. Was plenty to get the refrig cold for the next day.

I like to watch TV at night after my wife goes to bed. The generator would keep her up during outages so I wound up turning it off. Not a big deal but an example.
There are also people with medical devices that need to run 24/7. My neighbor is one and their generator runs 24/7 during an outage.

 

[Vines]

As I just posted, makes no sense to me, and I have done quite well surviving power outages in winter with my generator only running a few hours a day. Kept refrig plenty cold.

This for me all goes back to cost. For some, with plenty of money, great, they can guy whatever they want. But for the normal person, IMO, generator is the best solution, which is why I bought mine over batteries when I had a choice. But batteries are sexy. A tesla is sexy. Great, I am just practical and frugal.

Different cases for different folks.

Try that same experience in a snowstorm, when you need heat to survive. Fortunately, we won't see those conditions in California unless in the high sierras.

Remember, if your powerwalls freeze, you will not be able to take a charge from PV. However if you have extra power from a generator, you could use this to activate the internal Powerwall heaters.

If you have no power in the Powerwalls at the end of the day, and little solar due to winter exposure, you will have difficulty recovering this system in a winter storm, where PV generation is low.

For the couple hours you may have PV, the powerwalls may be so cold that they cannot take that charge. If they cannot take that charge, they will turn off the PV with frequency shifting. If you have a generator you can get the batteries warm for an hour or so, then they can activate the full PV load that you may get for a couple hours. If you don't get any sun, you can at least recharge the ESS so to keep the house warm and keep the Powerwalls warm so they will accept a charge.