Tesla PowerWall without Solar

[spacexfan]

That is why California has lower per capita electricity use.

WOW we in Florida pay a flat 12c per kWh. Thank god we don't have too much solar power and a great and reliable utility company (FPL).
You guys in California are quite crazy people. We down here burn coal and natural gas to enjoy a nicely cooled home and heated pools (and we soon get a new nuclear plant, the AP1000... awesome!). :biggrin:

 

[Kbra]

I think some of this PowerWall rational has to relate to the do i buy a Leaf or a Tesla. Both are electric cars but do you WANT a Leaf? Not likely. The Powerwall for most people wont pay for itself anytime soon but its a feature to have for those who want it. Plus im sure its considered "cool" to have.

 

[GreenPenguin]

I work from home several days out of the week, so the majority of my usage is during the peak day time hours. Especially in the summer when the AC is on.




It was the hour between 4:00 and 5:00PM on a Thursday in August 2014. It was 101 outside so my AC was probably on full blast. I don't remember what was going on that day, but I was thinking about turning everything on in the house - including the AC - and leave it on for an hour to see what that kind of load looks like.




The ROI would be worth it if I could get away with using no more than 2 PowerWall's. But to do that I would have to watch my usage throughout the day and try to stay under a 1kW an hour. I could do that in the winter, but in the summer that would be almost impossible. My AC consumes about 2.5kW's an hour, so having just 2 PowerWall's wouldn't work for summer use.

But I might do it anyway just to be closer to off the grid living.

Know you don't want to hear it but solar panels would help keep you out of tier 3 and tier 4 (not needing to do a complete offset) and you don't need to worry about time of use as it looks in your situation you can't really change your usage behavior.

Need to do the math as switching to TOU w/o solar, w/o usage behavior change, and only partial offset from a powerwall you may end up paying a lot more in that new rate plan then with your current standard tier rate!

The peak rates are really high!!! $.46 for summer peak (starting next month)! (SoCal).

Again with solar, you can generate at that rate but if you're consuming instead you'll start raking up a huge bill real fast! So be careful!

 

[Alexander]

Know you don't want to hear it but solar panels would help keep you out of tier 3 and tier 4 (not needing to do a complete offset) and you don't need to worry about time of use as it looks in your situation you can't really change your usage behavior.

Need to do the math as switching to TOU w/o solar, w/o usage behavior change, and only partial offset from a powerwall you may end up paying a lot more in that new rate plan then with your current standard tier rate!

The peak rates are really high!!! $.46 for summer peak (starting next month)! (SoCal).

Again with solar, you can generate at that rate but if you're consuming instead you'll start raking up a huge bill real fast! So be careful!

I know... I want solar, I need solar, but it will be awhile before I get it. I could write paragraphs on the topic of why I have to wait. I'm not happy about it, but at the moment and for the foreseeable future it just doesn't make sense. That's all I'm going to say

 

[Raffy.Roma]

I agree with the OP that the Powerwall is useful also without solar but I would like that Tesla offered also a solar power system together with the Powerwall.
Elon has also Solar City. So why Tesla doesn't offer also a high performance solar power system together with the Powerwall?

 

[Robert.Boston]

I agree with the OP that the Powerwall is useful also without solar but I would like that Tesla offered also a solar power system together with the Powerwall.
Elon has also Solar City. So why Tesla doesn't offer also a high performance solar power system together with the Powerwall?

Tesla isn't offering the PowerWall as a retail product; it's sold only through a Value Added Reseller (including SolarCity). I think, therefore, it's sensible for Tesla Energy not to bundle PowerWall and solar panels: that's the VAR's job, if that's what the retail customer wants.

 

[spacexfan]

So Alexander, did you decide to buy the Powerwall? What was your final decision? It would be awesome if you share a little info. But it is up to you, if you don't feel comfortable with it, it is fine.

 

[nwdiver]

Am I missing something or is the power wall intended to be used with only a DC-DC converter? That means no charging without solar and no supplying without a grid-tie inverter. The basic concept is ingenious since you're using equipment you already own (if you have solar) and just adding storage. I would imagine that a ~2kW DC-DC converter is significantly less expensive than a 240vac => 350vdc charger or a 350vdc => 240vac grid-tie inverter.

This also means that you can't charge the power wall at night....

 

[Ampster]

Am I missing something or is the power wall intended to be used with only a DC-DC converter? That means no charging without solar and no supplying without a grid-tie inverter. The basic concept is ingenious since you're using equipment you already own (if you have solar) and just adding storage. I would imagine that a ~2kW DC-DC converter is significantly less expensive than a 240vac => 350vdc charger or a 350vdc => 240vac grid-tie inverter.

This also means that you can't charge the power wall at night....

Technically the PowerWall contains a DC to DC converter. I am kind of foggy on the exact relationship of the DC to DC converter but I have heard it has communication capability and that may be how it communicates with the inverter. As far as I know it can only be used with an inverter that has a 350V DC bus. It connects to the SolarEdge inverter via that bus. Without an inverter you wouldn't have a useful battery pack. Without solar you couldn't charge the PowerWall unless you somehow used a 350V DC power supply to power the bus. I think that would be expensive and inefficient.

Somehow on a larger scale the Powerpacks couple with an inverter that also serves as a charger. Those devices are used for load shifting.

 

[wayner]

I live in Ontario and have looked at a PowerWall to arbitrage TOU pricing but it doesn't make any sense here since the differential between peak and off-peak is only C$0.08. The payback period is insanely long. That may be because a lot of our power is generated from hydro and nukes with no variable cost.

I am just installing solar but that will all be sold back into the grid as I can sell it for $0.38/kWh vs an all in peak cost of about $0.21KWh. Powerwall might make sense as a backup but it wouldn't last long so if I really cared about backup power a NG generator would be the way to go.

 

[Ampster]

I am not sure where the $0.08 comes from. You didn't state your off peak rate. Am I correct that you can sell back at $0.38 versus consume during peak at $.021? That is a $0.17 difference. What is your off peak rate? That is what your arbitrage difference will be based on. Think of every kWhr of load during your generation hours as reducing the amount that you get paid for your solar. If you could offset your loads then and recharge your batteries during the off peak rates there may be a shorter payback

 

[wayner]

I am not sure where the $0.08 comes from. You didn't state your off peak rate. Am I correct that you can sell back at $0.38 versus consume during peak at $.021? That is a $0.17 difference. What is your off peak rate? That is what your arbitrage difference will be based on. Think of every kWhr of load during your generation hours as reducing the amount that you get paid for your solar. If you could offset your loads then and recharge your batteries during the off peak rates there may be a shorter payback

The current differential between peak and offpeak is $0.08 as my current pricing is $0.080/kWh for off-peak and $0.161 for peak. There are various other surcharges that add up to roughly $0.05/kWh so the max price that I pay to purchase electricity is about $0.21/kWh. In Ontario we have something called the MicroFIT program to encourage homeowners to install solar panels where I can install up to 10kW of panels (which I have done) and sell the power for $0.384/kWh for twenty years.

But it doesn't make sense for me to use batteries to store the solar power given the MicroFIT program in Ontario.

 

[Ampster]

I am not talking about using batteries to store solar. I am talking about maximizing your revenue by using batteries to offset your consumption during peak so all of your solar production gets the high rate. If you are on a separate meter that won't work, only if net metered.

My illustration also goes to the point of the title of this thread, using the PowerWall without solar. I am not trying to convince you to do this because I don't know what your net consumption is and whether you have a credit balance. I am trying to illustrate that there are other options to just using a PowerWall to store solar.
Yes, without solar your rate differentials make for a long payback for storage.

 

[miimura]

@Ampster - the Ontario MicroFIT is basically a subsidized Feed-In Tariff system that buys your power at above market prices. In that case, you just have a meter on your solar and collect your money. Your consumption is completely separate. It is a very foreign system to us Californians who have Net Metering.

 

[bwa]

@Ampster - the Ontario MicroFIT is basically a subsidized Feed-In Tariff system that buys your power at above market prices. In that case, you just have a meter on your solar and collect your money. Your consumption is completely separate. It is a very foreign system to us Californians who have Net Metering.

I love the simplicity of it. In any system designed cheaply where the utility mandates the house go dark even though there's sufficient solar supply for it during blackouts or utility maintenance, then the above actually is slightly simpler and less overall downtime. Not much, but slightly. And it's damn simple.

Of course, I still prefer more expensive installations which allow the house to run off of solar during blackouts, something which doesn't tend to be the default least-cost installation in most cases.