tesla home battery/ solar question

tesla home battery/ solar question

We are getting solar panels very soon. Would we need a particular solar panel or connection in order to get the solar power to connect to the battery that will hold the energy? I don't want to get all this work done and find out I can't hold the energy because of x, y or z......

I look forward to the possibilities !!!!

jstack6 | 1 April 2015

You will need an Inverter that can run on and Off GRID like the OutBack or even Micro Inverters like Enphase that have that feature. They also need to put in an automatic cutoff switch that lets you run disconnected from the GRID when power fails so you aren't trying to run the entire neighborhood.

Your local Solar companies will know about these features. If not call SolarCity who is set to use the Tesla batteries.

ken | 1 April 2015

I have Enphase micro-inverters on my solar panels on two homes and absolutely love them. If you haven't yet decided on which panels to use, you should consider them. I have been using them on one home for 5 years. It keeps you from having to install a huge inverter that all panels feed into. They send you monthly reports on how much power they capture and the offset to carbon emissions. I think they will be great when I get my MX and the home battery system. Also, they came with 25 year warranties. I am very pleased with Enphase and am looking forward to being totally off the grid with Tesla's home power system. This is one persons experience for five years, but I think they are the way to go.

grega | 1 April 2015

@jman, If you're getting the solar panels soon... I'd wait till the Tesla announcement at the end of the month.

That said, it probably won't change what you plan short term. I would imagine the release of battery will have an initially higher cost and time delay to it and you might be better 'adjusting' your setup in 2 years time.

And what @jstack6 said :)

JGB | 2 April 2015

Our old diminished car batteries are going to become the uninterrupted power supply systems for home-owners. If you live in an area were power failures are common an old 60 or 85 is just the ticket.

mb30 | 3 April 2015

@Ken - I have the same enphase system and agree with your assessment. I've only been hooked up a little over a year but i'm very happy. I did hear though, and i dont know if this is true, that hooking up a battery back up system to micro inverters is more difficult. Someone even told me that it's currently not possible with the technology that is out there. I never bothered to look into this at all because we were not interested in the technology that is currently out there for stationary storage. I'm hoping that this new release will work with my system, make sense financially and allow me to go off grid. I guess i'll just have to wait and see like the rest of you :)

ken | 3 April 2015

@mb30 - Those are good questions to ask when the home storage system is announced which I think, and hope, will be the April 30th announcement.

grega | 3 April 2015

Agree JGB that the old batteries can be used quite well, and without a refurb of the cells themselves.

There's a charity group that takes old car batteries and does this for Indian schools now - but it actually breaks down each car battery to make these tiny units (not sure size... 1kWh? 4 kWh?). I remember wondering how a school could run on a battery so small - but they use laptops and low power devices.

60kWh would keep a home going for days and that's not really required for most people with unstable power (but if people want to pay more, go for it!)

bryan.whitton | 3 April 2015

@mb30 It is possible, but you will need another inverter to create a micro-grid. I am the Product Manager for our solar PV product line. We make a micro inverter that can handle a larger solar module than the Enphase M250 but very equivalent for themost part but we are in the process of developing a Net-Zero inverter that will act as its own utility generating 60hz. 240Vac single phase to supply the equivalent of the utility for a home.

It should be out in less than a year.

mark.morin | 23 April 2015


If installing PV system now, what are the options to ensure capability with Tesla home battery? It sounds like you are saying the Enphase M250, which we were considering, won't be compatible.

swenmichael56174 | 5 May 2015

I've been a designer of solar PV systems for 15 years. When the Enphase product came into being I was excited. It's a concept that allows easy adding of panels later for a lower cost and as you're ready to expand. Enphase also overcomes shadowing effects that can lower production drastically.

After spending MANY HOURS researching (online, calling Enphase tech suppport, talking to industry experts) I decided, what the heck.. I'll try it anyway. The good news is that it works, the bad news is you STILL NEED ANOTHER BATTERY INVERTER, and it sucks.

3 big Problems:
1. Power surges- since the Enphase is designed to stop producing power during times the grid is not reliable, and large appliances starting up (surging) will cause the Enphase to stop making power for a few minutes. So when you add up every large appliance (water heater, AC, fridge, freezer anything with a large motor/compressor) and consider they're all surging at different times that ALOT of energy loss throughout the day.

2. Still need a battery inverter- Enphases are grid-tie only, so they convert DC to AC...that's it, done. To use ANY GRID-TIE INVERTER with batteries, you need to feed the Enphases (or proper grid tie inverter) to a critical load panel (your emergency/or peak power management loads), that critcal load panel will be fed by the output of a seperate Battery Inverter of which the grid feeds it's input. The process is called "AC Coupling" You'll need an inverter with as many watts as you have solar PV AND as many watts as you need to backup.

3. Also, doing what I just said will void your Enphase warranty.

In closing Enphases are awesome if you're grid-tie only. DO NOT USE THEM WITH ANY BATTERY.

P.S. I think I should apply to be a Tesla rep...

ken | 6 May 2015

@swenmichael56174, your evaluation of the use of Enphase is very informative. I have never noticed any drop off during the start up of AC units, frig, etc. I am going to observe that within the next few days and get back to you. One of the reasons that I went with Enphase was the 20 Year warranty and the fact that one micro-inverter could go down and the others would continue to produce electricity. I also am going to contact my solar representative since I am very interested in using the Powerwall. I will get back to you on this.

bryan.whitton | 9 May 2015

@mark.morin Just noticed your question, You are absolutely correct, there is no way to use any micro inverter alone with a battery to augment or use as a backup.
Having said that, you can use them in conjunction with a hybrid inverter that allows for an AC coupling such as the Outback Radian or the Schneider XW series. This will add $15K - $20K to the cost of install but will allow for a near seamless whole house UPS.
Now, I work for Darfon America ( we make a micro inverter, MIG300, that competes head to head with the Enphase M250. So I am going to make a plug for our side at the same time.:-) For battery backup, micros at this time are not the hot setup UNLESS you go the route I have mentioned. @swenmichael56174 has said the same thing and has very useful information that goes along with what I am saying.

Dr. Pete | 9 May 2015

What am I missing here? Tesla will sell the PowerWall in 7 and 10 KWh sizes for home use. We already have two battery storage systems in our garage totalling 170 the form of two Tesla Model S vehicles. Since our main goal in getting a PowerWall system would be as backup in case of a temporary power outage, why would it not be possible to isolate our home from the grid with a simple on/off switch and wire our single 220V garage outlet to feed power back into the house from one of the Teslas. For a longer outage, we would unplug the depleted Tesla and plug in the second fully charged Tesla. I'm no electrical engineer (I don't even play one on TV), so perhaps an electrical engineer or electrician could enlighten me.

grega | 9 May 2015

Hi Pete.
There is an engineering requirement to what you're asking, but I think the question is equally (or more) concerned with human engineering.

The best analogy I can come up with (so far) uses my laptop. It has more battery than I need (mostly) - so if there was a power outage, in what situation would I want my PVR to drain my laptop battery so that it could keep recording my TV stuff?

Similarly, in what situation would I like my living room light to drain my laptop and phone batteries, to keep my home lit?

I don't mean to make a judgement in the above. I can see times I'd like my PVR to keep recording, but it's a trade off on losing my laptop battery - just as running my home would trade off the Tesla battery. In a major power outage, my car having full charge might be more important.

Guy2095 | 10 May 2015

"Similarly, in what situation would I like my living room light to drain my laptop and phone batteries, to keep my home lit?"

Too easy, you plug in a USB LED light to read hardcopy to keep working on that important report that's due in the morning.

Dr. Pete | 10 May 2015

When the power goes out we not only lose power to our refrigerator and freezer, but we also lose power to the pump that supplies our water. Since we also have an ICE car (that currently gets little use because we much prefer to drive our Teslas) it is more important to us to tap the power in our Teslas' batteries to run the refrigerator/freezer and water pump and drive our ICE car.

Guy2095 | 11 May 2015

Or instead of asking Tesla for an inverter to power your house you could ask the ICE manufacturer and power it from that so you can continue to enjoy driving the Tesla.

Dr. Pete | 11 May 2015

OK, I'll bite. How do you power your house with an ICE car?

rlwrw | 12 May 2015

OK, I'll bite. How do you power your house with an ICE car?

Same as a gas powered generator except with a tap on the alternator.

kenjing | 23 June 2015

I think the tesla batterys are at few hundred volts so you'd need a dc to ac converter down to 120V or 220V. But it should be possible but you'ld probably have to hack up your car or do some clever stuff to make it seemless. this would probably be good to offload a/c. But if you can afford a tesla you probably don't mind your ac bills anyhow. But it would ba good hack for emergencys or for the fun of it if you don't mind voiding your warranty. So maybe good for salvage shoppers.

chris | 24 June 2015

could this battery be used on a houseboat? Using Trojan L16H-AC deep cycle 6 volt now , with a Freedom 5W Inverter/charger. Dont know much about system as was on boat when I bought, but time for new batteries and thought this might be an option. Any input would be great.


Red Sage ca us | 24 June 2015
Shad_dash85 | 25 June 2015

I'm not sure micro-inverters will work since they output ac not dc. They batteries are dc and require dc from the panels.

rlwrw | 26 June 2015

Local news reports that the Gigafactory is actually ahead of schedule, and meeting the requirements for the financial incentives.
Also recently reported that Panasonic will be bringing in some of their battery people in August.

03Insight | 11 July 2015

My (4)L-16s, 12v batts (off grid here) are DEAD! Trace Engineering inverter/charger; two AC inputs doing well ^15 years. Reserved a Powerwall today ... get me out of lead-acid puleaze! Advise appreciated.