MASTER THREAD: Powering house or other things with Model 3

[golfcart]

A generator is going to be much cheaper, if you want to just run your fridge and a few outlets. Whatever value or not you see in powerwalls is up to you. My point is, that people will say "but the competition is doing X" and either not know, or not mention, that for some of these new systems its "thousands" of dollars additional, with hardware etc.

No doubt there will be some surprised people when they read the fine print on V2H… that is a fair point.

Solar panels are the same way, my neighbors all think I’ll still have power if the grid goes down because of my solar panels but of course I won’t because I haven’t spent an additional $30k+ on 3 power walls that can handle the startup loads from the HVAC unit etc… there is just no objectively good value for me from power walls. I don’t have a TOU plan, electricity is $0.11/kWh here, and we’ve lost power (for longer than an hour) twice in the 12 years we’ve been in this house.

These sort of low frequency events like hurricanes that knock out the power once every 5-10 years are just hard to plan for cost effectively I guess. I’d just rather not spend money on stationary batteries I use once in a blue moon when I’ve already got a huge battery sitting in my car. I only want to be able to park my car and plug it into my house to store solar power in the rare event that we lose the grid for days at a time. So I’m still gonna hold out hope for a reasonably priced solution from Tesla though y’all have made a lot of good points on why it’s unlikely to happen.

 

[NikolaTs]

some of the new solar inverters (Enphase IQ8 as an example) offer 'sunlight backup' where they can form a microgrid to power a critical loads panel if the grid goes down. but it's the same challenges everyone in this thread laid out: the smart controllers and switches etc come to 3K ish of additional electrical components to make it safe to connect to a main panel and auto switch on and off etc, and about 3K of electrical labor. so that's 6Kish just to use the power already being generated on your roof to power a few small loads like fridge modem and lights. It's basically 90% of the same labor to get a small amount of power to the panel as full home battery backup, but it only generates a few hours a day if it's not cloudy out or covered in snow.

As much as I'd like to tap into the 87kWh battery in the MYLR in my driveway at night, and use solar panels during the day it's not feasible today. As others have pointed out a fossil fuel generator is still the best bang for your $, but saving that, I was thinking a simpler solution for tinkerers could be something like a small backup battery like a bluetti hooked up to a fridge and modem, and charge it slowly as needed from a 12v inverter hooked up to the car. Has anyone tried that in a pinch? It's a lot of losses going 12v DC > AC > backup battery DC > AC load.

Otherwise, a LiFePo 5.1kWh battery with BMS can be had for 1,500, buy an AC charger to keep it topped off for emergencies, & an inverter to make it useful for emergency backup and you might be able to get away with a small DIY battery backup for around 2K. And if it runs out of juice recharge it slowly from the car's 12v, keeping it under like 600w draw.

Anyone found a better solution for emergency backup of small loads?

 

[jjrandorin]

Yeah but what’s a power wall cost? $12k? And it doesn’t do much of anything that the Ford system won’t do unless you buy 2 or 3 of them. I guess a Generac is probably better than either in a pure cost analysis if you want all your creature comforts but I still don’t see this as a terrible value.

I didnt address this question, but I got my 2 powerwalls in Jan of 2020 to go along with existing solar. I had ordered in October of 2019. At that time, tesla was still selling powerwall installs separately, meaning you could buy powerwalls with existing solar.

My cost for the 2 powerwalls, including all installation, etc through tesla was $18,235 and change. That doesnt count the tax credit I am getting back from them on my taxes, which on that amount is $4741. That makes my "installed, final cost" on the two powerwalls $13,494.

Through third party installers, even at that time, 2 powerwalls, installed, before tax credit, were about 22-24k (we never got to talking about if that was "after tax" or not, since the cost was so different.

Now, however, tesla only sells them bundled with solar, and third party installers charge roughly 12k per powerwall. I was personally never going to have a generator (not interested in the process of using one), and during fire season here now we sometimes get our power shut off by the utility for safety reasons (power safety shut offs, they call them). Most of CA is subject to these now at some level.

We can also price shift expensive peak power (up to over 50c a kWh from 4-9pm) to off peak time by using power from the solar and the powerwalls

Just like any other construction project in your home, you have to decide if it makes sense, for you, based on your specific wants and needs. I am completely happy with mine for the 13.5k I paid for 2 of them "out the door". I would be happier still if I could use my car(s) to supplement them, I just dont think its happening any time soon (if ever) from Tesla, and if it ever does, it will be for people already in the ecosystem (or with a 5-7k additional purchase like that ford F 150 sunrun deal.

 

[stopcrazypp]

some of the new solar inverters (Enphase IQ8 as an example) offer 'sunlight backup' where they can form a microgrid to power a critical loads panel if the grid goes down. but it's the same challenges everyone in this thread laid out: the smart controllers and switches etc come to 3K ish of additional electrical components to make it safe to connect to a main panel and auto switch on and off etc, and about 3K of electrical labor. so that's 6Kish just to use the power already being generated on your roof to power a few small loads like fridge modem and lights. It's basically 90% of the same labor to get a small amount of power to the panel as full home battery backup, but it only generates a few hours a day if it's not cloudy out or covered in snow.

Yeah, that's the same issue I have with this. If you spend $4k+ labor on this, that's pretty much almost all of the cost of getting a controller/inverter set up for battery backup (minus the batteries). That's quite a bit different than something that actually comes for free (or close) and you just plug in something and it powers your house.
The cheapest way would be to have a plug in the car like a generator does, then you can get a transfer switch or interlock kit installed (which can be used also for a generator), but I don't see automakers going that direction (they probably will like something more "smart").

As much as I'd like to tap into the 87kWh battery in the MYLR in my driveway at night, and use solar panels during the day it's not feasible today. As others have pointed out a fossil fuel generator is still the best bang for your $, but saving that, I was thinking a simpler solution for tinkerers could be something like a small backup battery like a bluetti hooked up to a fridge and modem, and charge it slowly as needed from a 12v inverter hooked up to the car. Has anyone tried that in a pinch? It's a lot of losses going 12v DC > AC > backup battery DC > AC load.

Yep, someone did exactly that recently in another thread, using a Yeti.
Is the 12v port in the center console connected to the main battery pack?
The only thing I noticed is that you can perhaps reduce cable losses by having a shorter 12V cable and having the battery inside the car and run a 120V extension cable out of the car, instead of a 12V extension cable (idea is less losses over high voltage for the same extension distance).

Otherwise, a LiFePo 5.1kWh battery with BMS can be had for 1,500, buy an AC charger to keep it topped off for emergencies, & an inverter to make it useful for emergency backup and you might be able to get away with a small DIY battery backup for around 2K. And if it runs out of juice recharge it slowly from the car's 12v, keeping it under like 600w draw.

Anyone found a better solution for emergency backup of small loads?

I'm exploring something like that too for my solar system. A permanent storage system is a lot more expensive because for older code you need at minimum a UL1741 SA listed inverter, and UL 1973 listed batteries (which some server rack style batteries packs are starting to get, but if you DIY with bare LiFePo cells for much cheaper, you won't be able to accomplish). With NEC 2020, only UL9540 ESS are allowed (basically a UL 1973 battery tested together with UL1741 SA inverter as a unit), which will drastically increase costs and reduce flexibility in choosing your components.
UL Issues First UL 9540 Certified Home Energy Storage System to Enphase Energy

There will have to be a race to get a storage system installed before all states adopt NEC 2020, although this is tempered by the fact there's not a whole lot of affordable UL 1973 listed battery options out there yet (especially in lower voltage 48V options, which tends to be less expensive).

 

[golfcart]

Yeah, that's the same issue I have with this. If you spend $4k+ labor on this, that's pretty much almost all of the cost of getting a controller/inverter set up for battery backup (minus the batteries). That's quite a bit different than something that actually comes for free (or close) and you just plug in something and it powers your house.
The cheapest way would be to have a plug in the car like a generator does, then you can get a transfer switch or interlock kit installed (which can be used also for a generator), but I don't see automakers going that direction (they probably will like something more "smart").

Not duplicating the batteries purchase is kind of the point though. Batteries are really expensive and depending on your situation those backup batteries are unused 99+% of the time. I'd rather use the huge battery I have already purchased in my car for those rare occasions that my power goes out. Say it is $5k but you get to claim a tax credit on it because it supplements your solar system... at that point it isn't THAT much more than a decent generator and still way cheaper than a couple of powerwalls.

But yeah, they make it sound like it is a cheap modification that you just plug in and it isn't. It would be nice if the advertising were a little more realistic.

 

[miimura]

Not duplicating the batteries purchase is kind of the point though. Batteries are really expensive and depending on your situation those backup batteries are unused 99+% of the time. I'd rather use the huge battery I have already purchased in my car for those rare occasions that my power goes out. Say it is $5k but you get to claim a tax credit on it because it supplements your solar system... at that point it isn't THAT much more than a decent generator and still way cheaper than a couple of powerwalls.

But yeah, they make it sound like it is a cheap modification that you just plug in and it isn't. It would be nice if the advertising were a little more realistic.

I agree that NOT duplicating batteries is the whole point of a V2H backup power system. However, I don't see how you can claim a tax credit on a system that does not itself contain batteries. The Investment Tax Credit that people can take on a Powerwall system is possible because it becomes part of the solar system and the batteries must be charged 100% from solar in order to qualify. I don't see how any part of the Ford Intelligent Backup Power system (or similar system) can qualify for the ITC.

 

[golfcart]

However, I don't see how you can claim a tax credit on a system that does not itself contain batteries. The Investment Tax Credit that people can take on a Powerwall system is possible because it becomes part of the solar system and the batteries must be charged 100% from solar in order to qualify. I don't see how any part of the Ford Intelligent Backup Power system (or similar system) can qualify for the ITC.

You are right that it wouldn't directly qualify. That is probably why an earlier poster said that Tesla has bundled powerwalls with the panel installation now. You might be able to get clever and add a couple of new panels to your existing array at the time...

 

[miimura]

You are right that it wouldn't directly qualify. That is probably why an earlier poster said that Tesla has bundled powerwalls with the panel installation now. You might be able to get clever and add a couple of new panels to your existing array at the time...

If you install Powerwall batteries alone when you have an existing solar installation, the whole PW installation qualifies for the ITC because the energy storage system is considered to be solar equipment. When you install a V2H system, you are not installing an energy storage system, you are installing electrical equipment. It would be very hard to connect a significant part of the installation equipment or labor to solar installed at the same time, with the possible exception of a main panel upgrade that would be required for the solar, absent the V2H functions.

 

[golfcart]

If you install Powerwall batteries alone when you have an existing solar installation, the whole PW installation qualifies for the ITC because the energy storage system is considered to be solar equipment. When you install a V2H system, you are not installing an energy storage system, you are installing electrical equipment. It would be very hard to connect a significant part of the installation equipment or labor to solar installed at the same time, with the possible exception of a main panel upgrade that would be required for the solar, absent the V2H functions.

This is where I am confused because I don't think that is true. This guide to the federal credit is clear to say that

"The solar PV system is new or being used for the first time. The credit can only be claimed on the “original installation” of the solar equipment."

https://www.energy.gov/sites/default/files/2021/02/f82/Guide%20to%20Federal%20Tax%20Credit%20for%20Residential%20Solar%20PV%20-%202021.pdf

Which makes me think that you can't get the tax credit on a powerwall either if you have existing solar. But I could be wrong. I assumed that was why Tesla was trying to bundle them now.

 

[miimura]

This is where I am confused because I don't think that is true. This guide to the federal credit is clear to say that

"The solar PV system is new or being used for the first time. The credit can only be claimed on the “original installation” of the solar equipment."

https://www.energy.gov/sites/default/files/2021/02/f82/Guide%20to%20Federal%20Tax%20Credit%20for%20Residential%20Solar%20PV%20-%202021.pdf

Which makes me think that you can't get the tax credit on a powerwall either if you have existing solar. But I could be wrong. I assumed that was why Tesla was trying to bundle them now.

Read the top left corner paragraph on Page 2 of the linked document. The installation of solar and energy storage do not have to be connected, or even in the same tax year to qualify. The energy storage system just has to be exclusively charged by on-site solar energy.

Energy storage devices that are charged exclusively by the associated solar PV panels, even if the storage is placed in service in a subsequent tax year to when the solar energy system is installed

 

[golfcart]

Read the top left corner paragraph on Page 2 of the linked document. The installation of solar and energy storage do not have to be connected, or even in the same tax year to qualify. The energy storage system just has to be exclusively charged by on-site solar energy.

Good to know. I guess that changes the math a bit. Does that mean you can't ever charge your batteries with the grid though?

 

[Evi_MX]

Always found it odd to consider using energy from your transportation when you are in a cautionary state just for convenience at home.

Same for gasoline. You pay a lot more per kwh it can produce (ideally) vs what you pay for electricity at home.

 

[TheTeachaMan]

I have always thought this should have been built in with our cars. Why buy a powerwall when you can drive your battery around?

Bi directional power flow through electric cars would add a whole new dimension to grid stability.

Completely agree! I mean, if Ford and Chevy can do it, can’t be all that hard! It I think you might have hit the nail on the head: if would undercut an important Tesla product category.

 

[brkaus]

Completely agree! I mean, if Ford and Chevy can do it, can’t be all that hard! It I think you might have hit the nail on the head: if would undercut an important Tesla product category.

All of them require expensive house modifications. Most aren’t going to pay for it, so limited interest. IMHO of course.

 

[jsight]

Completely agree! I mean, if Ford and Chevy can do it, can’t be all that hard! It I think you might have hit the nail on the head: if would undercut an important Tesla product category.

Do we know what the warranty looks like when used for this purpose?

 

[TheTeachaMan]

Do we know what the warranty looks like when used for this purpose?

On the Fords and Chevys? Nope. Haven looked that deeply at one.

 

[Xebec]

I've read through the entire thread but don't see any examples. Has anyone successfully tapped into the Subwoofer power source for powering an inverter?

My use case is I'd like to charge an Ecoflow Delta battery @ 200 or 300 watts while using that battery to power something like a fridge and/or a water pump, and I feel like this carries a lot less risk than tapping into the main battery.

Thank you.

 

[Thud]

Charging off the 12V lighter plug works to keep my Ecoflow River Plus charged up while running my garage refrigerator; but the 12V plug gets really hot. So I had to reduce the charge power (via Ecoflow app) to around 80 watts. Still barely enough to stay on top while running the fridge which occasionally spikes to 300W-400W when the defrost cycle kicks in.

I ended up getting a pair of 100W solar panels on Amazon (total $150) which I’ll use if the sun is out during a power outage.

I really hope Tesla a provides a decent powered inverter in their cars soon, even a 1500W plug would be a game-changer for emergency (or camping) use. I mainly would just use it to keep my portable batteries charged up so I can locate them around the house.

Cybertruck will supposedly have this capability, but there’s no reason not to bring at least a 120V plug to other models, but given how Tesla is constantly removing rather than adding features I don’t think this is likely.

IMO a portable propane generator makes much more sense for this use case but it seems like a waste to have this massive battery in my garage that can’t be effectively used for emergency power.

 

[stopcrazypp]

Charging off the 12V lighter plug works to keep my Ecoflow River Plus charged up while running my garage refrigerator; but the 12V plug gets really hot. So I had to reduce the charge power (via Ecoflow app) to around 80 watts. Still barely enough to stay on top while running the fridge which occasionally spikes to 300W-400W when the defrost cycle kicks in.

I ended up getting a pair of 100W solar panels on Amazon (total $150) which I’ll use if the sun is out during a power outage.

I really hope Tesla a provides a decent powered inverter in their cars soon, even a 1500W plug would be a game-changer for emergency (or camping) use. I mainly would just use it to keep my portable batteries charged up so I can locate them around the house.

Cybertruck will supposedly have this capability, but there’s no reason not to bring at least a 120V plug to other models, but given how Tesla is constantly removing rather than adding features I don’t think this is likely.

IMO a portable propane generator makes much more sense for this use case but it seems like a waste to have this massive battery in my garage that can’t be effectively used for emergency power.

Tesla doesn't generally want to warranty the traction battery for external power use, it's ok for trucks where there is a massive battery (plus power plugs are quite common for work trucks), but for regular cars, they probably don't want to deal with it. Ford seems to be doing a similar strategy (no power output for MachE, but yes for F150 Lightning).

 

[Jeff N]

Tesla doesn't generally want to warranty the traction battery for external power use, it's ok for trucks where there is a massive battery (plus power plugs are quite common for work trucks), but for regular cars, they probably don't want to deal with it. Ford seems to be doing a similar strategy (no power output for MachE, but yes for F150 Lightning).

I think 120V outlets with 1500W capability are going to become much more common. Kia/Hyundai already support this as an option in their newest EVs.