Grid Charge Powerwall with Solar

[brur]

The point I think that needs to be made, You are selling power back to the grid at .03 cents+-. Meanwhile, you spent a fortune for that opportunity?
Everyone would agree, importing grid at .03 cents to power up low batteries makes sense when the sky isn't so bright, just because the alternative looks so lousy by comparison.
If Tesla Powerwalls don't do that go elsewhere.

 

[JayClark]

This may double my replies I posted last night but are not showing up now. That's the E-13 plan look at the E-27 plan instead

https://www.srpnet.com/prices/pdfx/April2015/E-27.pdf

Okay, the E-27 is the same plan I'm on when I double checked my account, not sure how I ended up on that other document. I thought I had read somewhere that where SRP references "retail per-kWh price" in section G, that the term "retail" is implying an important price distinction that they don't use when indicating what SRP charges the customer...

• G - The kWh delivered to SRP shall be subtracted from the kWh delivered from SRP for each billing cycle. If the kWh calculation is net positive for the billing cycle, SRP will bill the net kWh to the customer under this price plan. If the kWh calculation is net negative for the billing cycle, SRP will credit customer for the net kWh at the retail per-kWh price under this price plan. For the purposes of this calculation, excess generation will be tracked by time-of-use period.

I.e... my understanding in the past, that SRP's use of the word "retail", only when referring to what SRP will credit to the customer, implies a much lower per kWr $ amount than what they charge when we use a KWr, but I'm having trouble finding any more detail on that now - so maybe I'm wrong.

So it's 1:1 credit, until such point as the customer has returned more than they received in a billing period, at which point they'll credit at the retail rate, what ever that is actually referring to.

Well, lets hope you can convince Tesla, would like to see how this turns out for you.

 

[aesculus]

I am getting a bit confused here so maybe I can summarize what I see as the ideal case in my particular situation:

I have limited solar (about 4.5 kw >> ~25kWh/day) in the ideal situation. My base consumption is about that without heating and AC loads, heating being the worst. Adding in the EV blows everything out of the water but when grid connected, NDB because I would charge off peak and would probably never charge if not grid connected. Planning of leaving the heat pumps off when not grid connected too but that is not germain to this post.

So rarely would solar by itself offset my total base load, especially in non ideal solar production months.

The ideal situation for me would be to charge my batteries with grid power when it's off peak and then send as much solar output to the grid when the price is right for selling. I don't want to buy power from the grid and resell it at a fraction of the cost.

So to net it out I would like to charge as much as I can from the grid off peak and then to sell my differential production of solar back to the grid since the price is right. Use the PW and off peak grid after I drain the PW, rinse and repeat next day.

I know people are doing something similar (less the grid charging) when the PWs are in cost mode with the cost scheduling, but I would like my cake and eat it too.

From what I understand this is not possible to do. I cannot for example tell the powerwall to charge up during off peak and then send back to grid during over solar production followed with PW discharge during peak and perhaps partial peak.

 

[brur]

There are inverters that will charge time of day, and do what you propose. Tesla, maybe not. I think you would find though that the Power company won't enjoy the relationship. And as in any unhappy relationship, it means you pay more than you get out.

 

[Fonzi03]

Just a snip for you guys to see. This is my technical contact with my installers.

 

[jjrandorin]

Just a snip for you guys to see. This is my technical contact with my installers.

Your also ok with the shorter warranty on the powerwall, it sounds like?

 

[Xminus6]

I am getting a bit confused here so maybe I can summarize what I see as the ideal case in my particular situation:

I have limited solar (about 4.5 kw >> ~25kWh/day) in the ideal situation. My base consumption is about that without heating and AC loads, heating being the worst. Adding in the EV blows everything out of the water but when grid connected, NDB because I would charge off peak and would probably never charge if not grid connected. Planning of leaving the heat pumps off when not grid connected too but that is not germain to this post.

So rarely would solar by itself offset my total base load, especially in non ideal solar production months.

The ideal situation for me would be to charge my batteries with grid power when it's off peak and then send as much solar output to the grid when the price is right for selling. I don't want to buy power from the grid and resell it at a fraction of the cost.

So to net it out I would like to charge as much as I can from the grid off peak and then to sell my differential production of solar back to the grid since the price is right. Use the PW and off peak grid after I drain the PW, rinse and repeat next day.

I know people are doing something similar (less the grid charging) when the PWs are in cost mode with the cost scheduling, but I would like my cake and eat it too.

From what I understand this is not possible to do. I cannot for example tell the powerwall to charge up during off peak and then send back to grid during over solar production followed with PW discharge during peak and perhaps partial peak.

It is not currently possible. I asked my Tesla Energy rep about this specifically and I just participated in a thread on TMC asking this exact question. Tesla will not allow you to charge from the Grid during Off-Peak then subsequently consume that stored energy during your Solar generation period to maximize your Solar sell-back. From what I was told this is a five-year limitation.

What you do end up doing is arbitraging between your cheaper Solar generation period to offset your Peak consumption. So you do get arbitrage but only from Solar to Peak. For those of usin PGE country, I think the change of Peak schedule actually benefits Battery Storage owners. Now Peak extends into the night so you can now offset expensive electricity even when the sun is down. You do get a savings, and that savings combined with the SGIP rebate would outpage denying the rebate and arbitraging between Off-Peak and Peak. I haven't done the math but from my rough estimates earlier it looks true, for me.

 

[PBBear]

It is not currently possible.....Tesla will not allow you to charge from the Grid during Off-Peak then subsequently consume that stored energy during your Solar generation period to maximize your Solar sell-back.

It IS possible - our powerwalls in Australia, and several other jurisdictions, are allowed to and do exactly this. It is administratively disabled in many USA territories, for reasons, possibly only USA-specific-tax-reasons.

 

[Xminus6]

It IS possible - our powerwalls in Australia, and several other jurisdictions, are allowed to and do exactly this. It is administratively disabled in many USA territories, for reasons, possibly only USA-specific-tax-reasons.

Right. It’s possible in the US too on a non-solar install i believe. I didn’t mean to say that it was physically impossible, just unactivated in software.

 

[JohnRatsey]

The underlying technology is there. I have the off-peak charging in the UK. However, it works to supplement the solar and how much charging gets carried out is determined by Tesla's opaque algorithms. The only time that off-peak charging is followed by discharge to the grid is when several days of poor solar output are followed by a sunny one.

I have requested Tesla support to provide better user-control of the off-peak charging so that solar generation forecasts can be taken into account (my main concern is the dull day following the sunny one) but this facility would be a step towards buying cheap electricity and selling it at a higher price. However, for optimal operation this also needs a user-control for deciding when/how much to discharge the battery to the grid (as opposed to just exporting solar generation). Does this facility exist?

 

[bob_p]

When we first evaluated our solar panel/PowerWall purchase (which could be installed next week), we had assumed we could use the PowerWalls to store grid energy and take advantage of "free nights" plans to run off solar during the day and charge the PowerWalls and our Tesla S/X overnight. Our installer said that wouldn't be allowed - and it turned out the restriction was because we were planning to use the 30% federal tax credit for our system.

However, after 5 years, if the restriction is lifted, we might revisit this - and by then we'll be deep enough into the 10 year warranty, that the total charging limit for grid charging won't have an impact on the remaining warranty.

Though it seems unlikely the utilities would really allow homes to use power only during the "free" periods and use no power during the day...

 

[Fonzi03]

Your also ok with the shorter warranty on the powerwall, it sounds like?

No shorter warranty on the wall. 10 year unlimited cycles guaranteed at 70% as long as not used in a commercial setting.

 

[Fonzi03]

It is not currently possible. I asked my Tesla Energy rep about this specifically and I just participated in a thread on TMC asking this exact question. Tesla will not allow you to charge from the Grid during Off-Peak then subsequently consume that stored energy during your Solar generation period to maximize your Solar sell-back. From what I was told this is a five-year limitation.

What you do end up doing is arbitraging between your cheaper Solar generation period to offset your Peak consumption. So you do get arbitrage but only from Solar to Peak. For those of usin PGE country, I think the change of Peak schedule actually benefits Battery Storage owners. Now Peak extends into the night so you can now offset expensive electricity even when the sun is down. You do get a savings, and that savings combined with the SGIP rebate would outpage denying the rebate and arbitraging between Off-Peak and Peak. I haven't done the math but from my rough estimates earlier it looks true, for me.

This is simply put not true. The rule is in place as a blanket so they don't have to manage it. However if your power company allows it and you put up enough of a fight they will enable it. I will send additional proof when mine is activated. They legally cannot prevent it from charging if power company allows it.

 

[Fonzi03]

When we first evaluated our solar panel/PowerWall purchase (which could be installed next week), we had assumed we could use the PowerWalls to store grid energy and take advantage of "free nights" plans to run off solar during the day and charge the PowerWalls and our Tesla S/X overnight. Our installer said that wouldn't be allowed - and it turned out the restriction was because we were planning to use the 30% federal tax credit for our system.

However, after 5 years, if the restriction is lifted, we might revisit this - and by then we'll be deep enough into the 10 year warranty, that the total charging limit for grid charging won't have an impact on the remaining warranty.

Though it seems unlikely the utilities would really allow homes to use power only during the "free" periods and use no power during the day...

If your power company allows it, the way the ITC rule is interpreted by me at least is as long as I use 100% solar to charge my panels...well first off I would be using 100% of my solar production to charge my panels. Secondly my power company also generates and stores solar energy in which I purchase...

 

[jjrandorin]

No shorter warranty on the wall. 10 year unlimited cycles guaranteed at 70% as long as not used in a commercial setting.

Thats not what it says when charging from the grid though.... I linked it earlier. Only solar is "10 years unlimited cycles". Any other combination is "37.8 MWh of aggregate throughput". It says that right on the first page of the warranty document I linked earlier:

https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_warranty_us_1-4.pdf

 

[neogeek]

If your power company allows it, the way the ITC rule is interpreted by me at least is as long as I use 100% solar to charge my panels...well first off I would be using 100% of my solar production to charge my panels. Secondly my power company also generates and stores solar energy in which I purchase...

I am having a hard time finding the ITC language, but Tesla's website says that the power walls need to be charged 100% by solar energy in order to receive the 30% ITC. You could be charging your PW with 100% of your solar array's capacity, but that leaves the possibility of grid charging which was part of your original post and in my opinion against the ITC.

A way this could be exploited (and why they are trying to prevent this in the US) is you could theoretically have one 300W solar panel giving 100% into your PW and grid charge the rest. The investment of actual solar generation compared to the investment of the PW and the ratios of solar:grid would abuse the solar ITC.

To your last part about utility's renewable portfolios, Yes some of your grid charging could be coming from renewable energy, but unless you are getting RECs (renewable energy credits) certifying as such, there is still a very likely chance that you are getting some non renewable energy from your grid. I don't know if this is still the case, but there was/is a commercial market for RECs and you will get businesses paying for RECs to say their companies run at a high percentage of renewable energy when they themselves don't have renewable systems to support it.

Also when would you grid charge? at night? Your options of your utility's renewable sources at night are likely more limited than during the day. Geo Thermal, maybe Hydro?

I would be interested to see how this plays out for you, but I think at best all you can do is discharge to the grid to still uphold the ITC. When the ITC expires, it will also be interesting to see "grandfathered" systems that took advantage of the credit being permanently locked out of grid charging, whereas solar/pw systems that were not eligible for the ITC being allowed. The gov't subsidized your system with that credit with the expectation that it will be used solely for renewable purposes. Their investment intent doesn't go away just because they aren't offering it for new customers.

 

[CA-Gbm84]

This is simply put not true. The rule is in place as a blanket so they don't have to manage it. However if your power company allows it and you put up enough of a fight they will enable it. I will send additional proof when mine is activated. They legally cannot prevent it from charging if power company allows it.

What law do you think they are breaking?

Just because you want it does not mean Tesla will change the way the product works. If you read Powerwall & The Grid section on this support page - it's pretty clear that in the US, Powerwall will not charge from grid when installed with solar.

Combining Systems | Powerwall Support

I agree its an administrative restriction - but what make you think they will change their policy for you?

My opinion - when the first Powerwalls hit their 5 year ITC requirement (2021) and there are thousands of customers with good standing to make the change, it will come then - until then they will do what's best for the majority of customers (protect the ITC eligibility).

 

[jjrandorin]

I know what you mean, but in all fairness it actually DOES charge from the grid in the US, but only during storm watch mode, and not under user control... so yeah its an administrative restriction.

For all we know, tesla may have this restriction to enable their product to even get the ITC (or SGIP in california). I have no idea, but could see a situation where, if the restrictions were not in place in the product, or were user selectable or something, the ITC wouldnt be allowed for anyone.

In any case, I am interested to see how this actually plays out when the OP completes his install and gets the system fully interconnected and activated. I suspect (but dont know) that tesla will tell the OP " its great that your utility is allowing this, but our product does not do this in the US as of yet". Tesla does not seem to do well with "exceptions" in my opinion... unless you are someone important enough to get elons specific attention.

Op, I would recommend taking a look at that warranty document I linked, since you mentioned that the PW has 10 years unlimited charging, which as far as I can see is incorrect if charged from the grid (that is, if you care about the length of the warranty period, which you may not).

Like I said, really curious to see how all this shakes out, so thanks for the updates OP!

 

[gpez]

I am having a hard time finding the ITC language, but Tesla's website says that the power walls need to be charged 100% by solar energy in order to receive the 30% ITC. You could be charging your PW with 100% of your solar array's capacity, but that leaves the possibility of grid charging which was part of your original post and in my opinion against the ITC. .

@neogeek You may want the 2018 IRS private letter ruling:

"This demonstrates that the Congress expects the energy used by a “qualified solar electric property expenditure” to be derived solely from the sun. Accordingly, 100 percent of the energy used by the Battery must be derived from the sun. If this is not the case, the Battery does not meet the definition of “qualified solar electric property” in the Code."

IANAL but it seems the door is open to an interesting argument if your utility is also 100% solar...

Just because you want it does not mean Tesla will change the way the product works. If you read Powerwall & The Grid section on this support page - it's pretty clear that in the US, Powerwall will not charge from grid when installed with solar.

Combining Systems | Powerwall Support

I agree its an administrative restriction - but what make you think they will change their policy for you?

"Change the way the product works" and "administrative restriction" seems contradictory. Either the product physically works this way and can't be changed or Tesla has made a policy decision to not enable that functionality. It's assuredly the latter as the same product in other jurisdictions can charge from the grid and of course here in the states it can charge off the grid when Storm Watch is on. Have you never had success convincing a company to alter policy or give an exception based on your specific circumstances? It's entirely possible (and extremely likely) that Tesla has the policy and notice you linked above to make it simple for 99% of it's customers given the IRS tax credit ruling but it's not like the Powerwall can't physically support this scenario - in fact it's probably just an internal setting change. I hope @Fonzi03 is successful in his negotiation.

 

[Fonzi03]

After many delays and power company losing paperwork I must claim success! See attached picture for powerwall grid charging. Will post tomorrow with grid charge and solar charge simultaneously just no sun right now.