SunPower Compatibility with Powerwall

[Mayer]

After reviewing other threads, I have learned that I am quite unknowledgeable about my 15.33 kW SunPower system.

After pricing out a generator for backup power last week (as recommended last year by my small/family/local solar installer here in Pennsylvania), I concluded a battery system makes more sense for my needs when the grid fails.

Today I located and emailed a Tesla approved and reputable Powerwall installer who will certainly answer my question on Monday but I’m wondering if my system is even compatible with the Powerwall.

Do I need to identify the inverter to answer that question?

All the paperwork for my solar system is at my office so I don’t know the inverter manufacturer but suspect it’s SunPower like the panels.

If the Tesla product is not suitable or compatible, what is the next best option for battery back up?

Here is a photo of the exterior equipment:

 

[jjrandorin]

Powerwalls are AC coupled so at least from what I can tell, they are inverter agnostic as long as the inverter is AC coupled and not a DC inverter.

 

[miimura]

I have yet to hear a credible report of a grid connected solar system that is not compatible with Tesla Powerwalls. You should be fine to get Powerwalls integrated with your Sunpower system.

 

[Mayer]

Do you envision a problem having it installed in a way that the batteries could be recharged during the daytime while the system is off-line, power grid, failure?

In other words, can the system go off grid to recharge batteries, while the grid is down?

 

[miimura]

Do you envision a problem having it installed in a way that the batteries could be recharged during the daytime while the system is off-line, power grid, failure?

In other words, can the system go off grid to recharge batteries, while the grid is down?

That is the normal way. It should be no problem as long as you get enough battery relative to your solar. Tesla recommends no more than 7.6kW of solar inverter capacity per Powerwall. So, with your 15kW system, you should get either two or three Powerwalls. More battery is better, especially if you want to survive power outages in the winter.

 

[BGbreeder]

After reviewing other threads, I have learned that I am quite unknowledgeable about my 15.33 kW SunPower system.

After pricing out a generator for backup power last week (as recommended last year by my small/family/local solar installer here in Pennsylvania), I concluded a battery system makes more sense for my needs when the grid fails.

Today I located and emailed a Tesla approved and reputable Powerwall installer who will certainly answer my question on Monday but I’m wondering if my system is even compatible with the Powerwall.

Do I need to identify the inverter to answer that question?

All the paperwork for my solar system is at my office so I don’t know the inverter manufacturer but suspect it’s SunPower like the panels.

If the Tesla product is not suitable or compatible, what is the next best option for battery back up?

Here is a photo of the exterior equipment:

View attachment 962513

While Powerwalls are likely to be completely compatible with your existing equipment, they may not solve your backup issue(s).

When do envision needing backup power? Winter time, when the solar production is at a minimum? When things are overcast due to a winter storm? Summertime, when you need AC? What loads do you want to support? (Laptops and some phones? Or a heat pump/AC and an electric range?) How long do you want to support being off of grid power?

I have three Powerwalls with enough solar to be a net exporter and for winter outages, that's enough for the frugal use for a day or two. (No heaters, just two fridges, an internet connection and gas heat.) The problem with winter outages for me, is that they seem to occur during bad weather, so the Powerwalls don't necessarily start the outage at 100%, but the solar production is down to 2-4% of peak production due to overcast. For you, that might mean getting by on 2.5kWh/day (guesstimate based on a week overcast preceding an outage event, and then overcast for awhile thereafter) of sustainable use for a longer term outage. (I also have some backup generators, but that's a different story.)

I think backup power comes down to what it would take to cut your home usage to bring it into line with what your solar might produce during a couple weeks of winter overcast. If you can't get by on your minimum solar (say my guesstimate above of ~2.5kWh/day), you need a plan B, which may be a generator.

For anyone considering a generator, I think it is worth also considering the frequency that you might need it, and whether a plan C of going on vacation, or moving to a motel / distant relative / an RV makes for a more suitable solution. The cost "per kWh actually used" on a generator can be extremely high; there is the capital cost, the installation cost, the yearly maintenance (filters, oil changes, including biweekly exercise cycles), any service contract, plus the running cost per hour of the fuel when you actually use it. For folks whose plumbing might freeze in a sustained outage, that might be easy to rationalize. Finally, generators function best when they are loaded to 50-100% of capacity, and starting noninverter ACs can be a compromise between enough generator power to start the AC, but not so much that generator loafs along at 10% for the rest of the time. A backup genersgor might reasonably include installing an inverter AC/heat pump.

I think that the decision process isn't simple, and generator sales people and installers aren't necessarily without vested interests in the outcome.

Finally, I would consider whether your backup generator fuel source is to be relied upon (e.g. propane, diesel/heating oil, gasoline, or natural gas). Propane long term storage works really well, but the upfront tank costs can be quite large depending on the generator size and for the duration you are planning for. Diesel can be stored for long periods of time with attention to detail. Gasoline sourcing and storage gets complicated if you plan on storing it for more than a year. Depending on where you live (e.g. Texas, California), an electrical outage for you might also eliminate your natural gas supply.

I think that other vendors of batteries do a much better job of integrating with generators compared to Tesla, which essentially doesn't support their use. (Very limited list of "supported models", and generally only for completely off grid scenarios.)

Just my $0.02, from someone who has gone through the process more than a few times.

All the best,

BG

 

[Mayer]

That is the normal way. It should be no problem as long as you get enough battery relative to your solar. Tesla recommends no more than 7.6kW of solar inverter capacity per Powerwall. So, with your 15kW system, you should get either two or three Powerwalls. More battery is better, especially if you want to survive power outages in the winter.

Thank you, and it makes sense that batteries recharge using panels during outage.

I presume there are threads discussing installation costs for two verses three Powerwalls; hoping cost to install second and third is reduced compared to installation costs for a single Powerwall multiplied three times.

If you know, I’m also wondering if it’s best to purchase Powerwalls directly from Tesla to ensure new and best product or better to purchase through installer.

 

[BGbreeder]

Thank you, and it makes sense that batteries recharge using panels during outage.

I presume there are threads discussing installation costs for two verses three Powerwalls; hoping cost to install second and third is reduced compared to installation costs for a single Powerwall multiplied three times.

If you know, I’m also wondering if it’s best to purchase Powerwalls directly from Tesla to ensure new and best product or better to purchase through installer.

Yes, the costs on the second and third Powerwall are lower; you already have bundled the cost of the controller (the gateway) into the cost of the first one.

Powerwalls aren't exactly sitting around on shelves at the moment, as the demand is too strong. I would choose the installer on other reasons. (Read other threads here on Tesla installation and support, compared to third parties.)

Good luck,

BG

 

[Mayer]

While Powerwalls are likely to be completely compatible with your existing equipment, they may not solve your backup issue(s).

When do envision needing backup power? Winter time, when the solar production is at a minimum? When things are overcast due to a winter storm? Summertime, when you need AC? What loads do you want to support? (Laptops and some phones? Or a heat pump/AC and an electric range?) How long do you want to support being off of grid power?

I have three Powerwalls with enough solar to be a net exporter and for winter outages, that's enough for the frugal use for a day or two. (No heaters, just two fridges, an internet connection and gas heat.) The problem with winter outages for me, is that they seem to occur during bad weather, so the Powerwalls don't necessarily start the outage at 100%, but the solar production is down to 2-4% of peak production due to overcast. For you, that might mean getting by on 2.5kWh/day (guesstimate based on a week overcast preceding an outage event, and then overcast for awhile thereafter) of sustainable use for a longer term outage. (I also have some backup generators, but that's a different story.)

I think backup power comes down to what it would take to cut your home usage to bring it into line with what your solar might produce during a couple weeks of winter overcast. If you can't get by on your minimum solar (say my guesstimate above of ~2.5kWh/day), you need a plan B, which may be a generator.

For anyone considering a generator, I think it is worth also considering the frequency that you might need it, and whether a plan C of going on vacation, or moving to a motel / distant relative / an RV makes for a more suitable solution. The cost "per kWh actually used" on a generator can be extremely high; there is the capital cost, the installation cost, the yearly maintenance (filters, oil changes, including biweekly exercise cycles), any service contract, plus the running cost per hour of the fuel when you actually use it. For folks whose plumbing might freeze in a sustained outage, that might be easy to rationalize. Finally, generators function best when they are loaded to 50-100% of capacity, and starting noninverter ACs can be a compromise between enough generator power to start the AC, but not so much that generator loafs along at 10% for the rest of the time. A backup genersgor might reasonably include installing an inverter AC/heat pump.

I think that the decision process isn't simple, and generator sales people and installers aren't necessarily without vested interests in the outcome.

Finally, I would consider whether your backup generator fuel source is to be relied upon (e.g. propane, diesel/heating oil, gasoline, or natural gas). Propane long term storage works really well, but the upfront tank costs can be quite large depending on the generator size and for the duration you are planning for. Diesel can be stored for long periods of time with attention to detail. Gasoline sourcing and storage gets complicated if you plan on storing it for more than a year. Depending on where you live (e.g. Texas, California), an electrical outage for you might also eliminate your natural gas supply.

I think that other vendors of batteries do a much better job of integrating with generators compared to Tesla, which essentially doesn't support their use. (Very limited list of "supported models", and generally only for completely off grid scenarios.)

Just my $0.02, from someone who has gone through the process more than a few times.

All the best,

BG

Very helpful!

I live in a wooded area with a steep driveway, so getting propane delivered days after a snow storm can be problematic (although the recent warming trend helps because we rarely have more than 2-3 days without temperatures going above freezing).

And of course we have power outages in the summer too, and the battery back up would probably work fine in summer but winter is certainly a concern.

Unfortunately, the generator would need to be placed on the opposite side of my house from the propane tank, so I definitely would need to bury a 500 gallon propane tank.

That is what brought the cost just about where it made more sense to go with the battery back up.

The price quoted for a 24 kW Generac Guardian was $13,000, without the propane tank installation and hook up.

We have a 3200 square-foot home, and (with teenage girls and pool) a very large carbon footprint, which is why I installed the solar panels last year.

And so I really appreciate knowing that the Tesla powerwall is not terribly compatible with most back up generators.

And yes, for the past 18 years we have been using the hotel, method or charging are iPhones in the car during power outages.

But suddenly everybody I live with thanks that is archaic.

Thank you for the insights!

 

[h2ofun]

Very helpful!

I live in a wooded area with a steep driveway, so getting propane delivered days after a snow storm can be problematic (although the recent warming trend helps because we rarely have more than 2-3 days without temperatures going above freezing).

And of course we have power outages in the summer too, and the battery back up would probably work fine in summer but winter is certainly a concern.

Unfortunately, the generator would need to be placed on the opposite side of my house from the propane tank, so I definitely would need to bury a 500 gallon propane tank.

That is what brought the cost just about where it made more sense to go with the battery back up.

The price quoted for a 24 kW Generac Guardian was $13,000, without the propane tank installation and hook up.

We have a 3200 square-foot home, and (with teenage girls and pool) a very large carbon footprint, which is why I installed the solar panels last year.

And so I really appreciate knowing that the Tesla powerwall is not terribly compatible with most back up generators.

And yes, for the past 18 years we have been using the hotel, method or charging are iPhones in the car during power outages.

But suddenly everybody I live with thanks that is archaic.

Thank you for the insights!

IMO, just depends on how one wants to spend their money. IMO, from a pure dollar and sense, putting in ANY of this stuff makes no sense.
But I have 7 powerwalls, never used so far, 30KW of solar, best investment I have made, and a 22kw whole house generator, on a 500 gallon propane
tank, which I put in before the solar and batteries. No matter what happens, I am covered. Makes the wife happy. Makes others when they have no power so they come to my house. Will I ever see my money back, NOPE, but could care less. I cannot take it with me, and its fun to "play" with.

 

[Mayer]

IMO, just depends on how one wants to spend their money. IMO, from a pure dollar and sense, putting in ANY of this stuff makes no sense.
But I have 7 powerwalls, never used so far, 30KW of solar, best investment I have made, and a 22kw whole house generator, on a 500 gallon propane
tank, which I put in before the solar and batteries. No matter what happens, I am covered. Makes the wife happy. Makes others when they have no power so they come to my house. Will I ever see my money back, NOPE, but could care less. I cannot take it with me, and its fun to "play" with.

My home was built with a 1k gallon propane tank for heat. Unfortunately, the 24 kW generator would be installed on opposite side of house so a second propane tank is necessary.

Is your 500 gallon tank dedicated exclusively to the generator?
Is it buried?
Do you still use the generator now that you have 7 powerwalls?

 

[CrazyRabbit]

during URI i, people had pipes freeze, lots of expensive damage. Nice to have propane space heaters for winter event like that.

 

[BGbreeder]

My home was built with a 1k gallon propane tank for heat. Unfortunately, the 24 kW generator would be installed on opposite side of house so a second propane tank is necessary.

Is your 500 gallon tank dedicated exclusively to the generator?
Is it buried?
Do you still use the generator now that you have 7 powerwalls?

On propane generators:

1. Locally, generator refills come after all the heating refills are fulfilled. So in a winter storm outage, there may (will) be an extended delay getting your generator tank refilled.
2. It is not a good idea to hook generators up to propane tanks used by other equipment. The startup demand in gas has been known to occasionally cause pilots to go out on other equipment.
3. Generators can run through a lot of propane. I would suggest that you download the Generac manual for the model you are considering, and go through their sizing recommendations, given your expected demand, and the number of days that you would like backup for. A 500 gallon tank only holds 400 gallons to begin with, but when it is cold, and the tank level gets lower, the tank can't absorb enough heat from the environment to vaporize enough propane as the tank level drops. So, you will have less propane capacity for winter backup. Putting your generator tank underground is a big help in this respect, or going to a larger tank.

All the best,

BG

 

[BGbreeder]

Very helpful!

I live in a wooded area with a steep driveway, so getting propane delivered days after a snow storm can be problematic (although the recent warming trend helps because we rarely have more than 2-3 days without temperatures going above freezing).

And of course we have power outages in the summer too, and the battery back up would probably work fine in summer but winter is certainly a concern.

Unfortunately, the generator would need to be placed on the opposite side of my house from the propane tank, so I definitely would need to bury a 500 gallon propane tank.

That is what brought the cost just about where it made more sense to go with the battery back up.

The price quoted for a 24 kW Generac Guardian was $13,000, without the propane tank installation and hook up.

We have a 3200 square-foot home, and (with teenage girls and pool) a very large carbon footprint, which is why I installed the solar panels last year.

And so I really appreciate knowing that the Tesla powerwall is not terribly compatible with most back up generators.

And yes, for the past 18 years we have been using the hotel, method or charging are iPhones in the car during power outages.

But suddenly everybody I live with thanks that is archaic.

Thank you for the insights!

I'm not sure that the decision is batteries versus generator. I would explore the budgets of both, and see how it shakes out. I would also get to know your local Generac installer(s) and figure out how competent they are. One thing that I like about some of the newer Generac models is that they have a quieter, low speed, self test mode. Bear in mind that for Generac, they divide their installers/dealers/repair depending on whether the engine is air cooled or water cooled, so it can be a different team. The liquid cooled technicians are dealing with large commercial units routinely and generally get a great deal of practice.

All the best,

BG

 

[Mayer]

I'm not sure that the decision is batteries versus generator. I would explore the budgets of both, and see how it shakes out. I would also get to know your local Generac installer(s) and figure out how competent they are. One thing that I like about some of the newer Generac models is that they have a quieter, low speed, self test mode. Bear in mind that for Generac, they divide their installers/dealers/repair depending on whether the engine is air cooled or water cooled, so it can be a different team. The liquid cooled technicians are dealing with large commercial units routinely and generally get a great deal of practice.

All the best,

BG

So, sounds like a liquid cooled model should be considered as the installer and their service team should be well versed in proper installation and maintenance.
Also, despite looking at Powerwall closely, if the intention is to install both a generator and a battery, Generac might be a better fit since it offers both products?

 

[BGbreeder]

So, sounds like a liquid cooled model should be considered as the installer and their service team should be well versed in proper installation and maintenance.
Also, despite looking at Powerwall closely, if the intention is to install both a generator and a battery, Generac might be a better fit since it offers both products?

Generators are a well established technology that continues to evolve. Generac has something like half of the US residential generator sales, so they are clearly meeting a need. Meaning, I think that Generac seems to make good products on both the air cooled and liquid cooled side.

I think that the generator plus battery (like a hybrid car) has some advantages. For better or worse hybrid backup is a new concept in home backup. On paper it ought to be simple; when the batteries are low, turn on the generator, when the batteries approach their upper limit of charge, turn off the generator. There are details that need to be addressed with respect to the generator- warm up time, cool down time, the output power quality, and especially feedback between the charging circuit of the batteries and the generator windings. (Harmonics and power distortion in particular, though frequency control is another big one in my mind.)

I don't know if Generac is a better fit; I have no experience with their battery systems. Personally, I generally, but not always, prefer a single vendor as it minimizes finger pointing. If I were doing it all over, I would certainly consider their solution seriously.

I would bear in mind that the minimum size of the batteries may be set by the maximum charge rate of the batteries in the context of what your maximum solar output (kW, not kWh) might be in April/May. Otherwise, you would need to shut your solar off, or shut parts of it off, to slow the charge rate to below the batteries maximum charge rate.

Good luck,

BG

 

[Ackman999]

I currently have a Sunpower system installed on my home, it includes a 13.5kw Sunvault battery and 10 400w solar panels. I have survived several summer power outages, and one extended winter ice storm outage that lasted 6 days. my summer outages did not take any intervention on my part as my AC is not one of the 12 circuits included in my backup configuration. When we lost power last winter, it was my first experience with the system so I was pretty conservative on my power consumption. I have an enclosed gas fireplace that has the capacity to keep my home comfortably warm so we were able to manage things easily for the duration of the outage.

 

[Mayer]

I currently have a Sunpower system installed on my home, it includes a 13.5kw Sunvault battery and 10 400w solar panels. I have survived several summer power outages, and one extended winter ice storm outage that lasted 6 days. my summer outages did not take any intervention on my part as my AC is not one of the 12 circuits included in my backup configuration. When we lost power last winter, it was my first experience with the system so I was pretty conservative on my power consumption. I have an enclosed gas fireplace that has the capacity to keep my home comfortably warm so we were able to manage things easily for the duration of the outage.

Any particular reason you decided not to use the Tesla Powerwall?

 

[Mayer]

I see. Sun Power manufactures SunVault

 

[Mayer]