Arizona Powerwall Installs

[SOULPEDL]

The software knows that later in the day I will pull from grid a little so it backfeeds grid at 2pm since there is excess. This offsets any grid usage later in the day.

Cool.... So this is a function of the 10% reserve you set?

Wondering, it seems strange to cycle your battery more and give back to the grid so that you can buy it back later. Not sure I follow. Keep in mind, the less you cycle the battery, the longer it will last.

 

[SOULPEDL]

Concern of mine .... if 4 PW2s in a closed 3 car garage, housing running >90% off solar + PWs, how much heat do the PW2s give off?

edit: the garage contains no ICEs. If it helps, 1st proposal from installer calls for 43288 kWh/12 months, 33 kW to run my house 100% solar. I figure I will knock that down substantially before install. My current power provider says 18 kW from the panels to supply 80% of my usage. They don't know about the batteries.

Now we get to figure out how to cool the garage. HOA probably has something to say there. Venting seems low hanging. My batteries will be against an interior wall at least.

We still have ICE (but one's a keeper). I hate it when we have to use the SUV and that hot engine adds a furnace to the garage.

If I could afford to go 100%, I would! As someone said earlier, they hate having to buy SRP power, and are now adding more panels (forgot who said it). But maybe go a bit under just so you have a new target to save energy.

 

[SOULPEDL]

Renting seems to use about the same price, maybe a nickel more per watt to rent. Basically, solar pricing hasn't changed at about $2.58/Watt.

But it's far from <$2 being discussed here "in some places" anyway. https://electrek.co/2019/04/30/tesla-solar-undercutting-2-per-watt-system/

So prices are dropping, but my install date is already Nov. So any more delays and I lose 4% on Fed.

My guess is that solar prices will drop in 30 days because they won't be able to guarantee 2019 completion dates. But a 4% drop only brings it down to $2.48/watt.

Oh, I get buyer's remorse everytime.

 

[D3xDt3Reaction]

Thanks for confirming. You just moved my theory closer to practice, and it does make sense it would cost more energy (not $) to pre-chill. I'm calling this a scam that hurts our environment, and no longer just my opinion.

I don’t know if they have intent to soak people here, but one other thing that’s a bummer is not being able to drive your bill below the minimum service charge of $32.44 per month even if you sell back lots of energy during peak. At least that’s the way I read it.

 

[Darwin]

I don’t know if they have intent to soak people here, but one other thing that’s a bummer is not being able to drive your bill below the minimum service charge of $32.44 per month even if you sell back lots of energy during peak. At least that’s the way I read it.

I don't think there's anything stopping you from having bills below the $32.44 service charge on SRP's E-27 and E-15 plans, although the rules can certainly get pretty confusing. I've had after tax bills in the spring that were below $32.44 (although not by much) on my 5.6kW/1PW system.

 

[Chancellor32]

Cool.... So this is a function of the 10% reserve you set?

Wondering, it seems strange to cycle your battery more and give back to the grid so that you can buy it back later. Not sure I follow. Keep in mind, the less you cycle the battery, the longer it will last.

By feeding back into the grid it negates any later pulls from the grid. In cost saving mode it attempts fo limit any and all pulls from grid so in the early afternoon I have excess and the battery is full so back to grid is only option.

 

[Chancellor32]

Renting seems to use about the same price, maybe a nickel more per watt to rent. Basically, solar pricing hasn't changed at about $2.58/Watt.

But it's far from <$2 being discussed here "in some places" anyway. https://electrek.co/2019/04/30/tesla-solar-undercutting-2-per-watt-system/

So prices are dropping, but my install date is already Nov. So any more delays and I lose 4% on Fed.

My guess is that solar prices will drop in 30 days because they won't be able to guarantee 2019 completion dates. But a 4% drop only brings it down to $2.48/watt.

Oh, I get buyer's remorse everytime.

Don’t rent, read the fine print. Prices can go up with a 30 day notice, after 7 years you would spent more renting that buying.

 

[Don TLR]

SRP isn't in the list of suppliers for rental solar, but not sure how firm that rule is.

 

[D3xDt3Reaction]

I don't think there's anything stopping you from having bills below the $32.44 service charge on SRP's E-27 and E-15 plans, although the rules can certainly get pretty confusing. I've had after tax bills in the spring that were below $32.44 (although not by much) on my 5.6kW/1PW system.

Interesting - that’s good news. My interpretation of page 5 of https://www.srpnet.com/prices/pdfx/April2015/E-27.pdf was that the floor was the service charge so good to hear an actual experience.

 

[Chancellor32]

Interesting - that’s good news. My interpretation of page 5 of https://www.srpnet.com/prices/pdfx/April2015/E-27.pdf was that the floor was the service charge so good to hear an actual experience.

It would be financial suicide though to purchase that much solar to have less than the $32 service fee. Anything over 50% offset doesn’t make sense when power is $.03-$.04. That’s dirt cheap and the ROI is basically 20+ years on an excess panels.

 

[Odiemac]

It would be financial suicide though to purchase that much solar to have less than the $32 service fee. Anything over 50% offset doesn’t make sense when power is $.03-$.04. That’s dirt cheap and the ROI is basically 20+ years on an excess panels.

Understand that some people are only looking at ROI, but isn’t there a lot of coal on the AZ grid?

 

[Chancellor32]

Understand that some people are only looking at ROI, but isn’t there a lot of coal on the AZ grid?

Totally but if I wanted to get 100% of my power from panels it would literally cost me $40-50k and I would still pay at minimum $32 a month plus whatever demand charge there was. One could do it but there is no ROI on that. Now if someone does it because they want to be 100% self sustainable then hats off to that person. I wish I could but I couldn’t justify the extra 20-30k and never see that money again.

 

[Darwin]

Interesting - that’s good news. My interpretation of page 5 of https://www.srpnet.com/prices/pdfx/April2015/E-27.pdf was that the floor was the service charge so good to hear an actual experience.

Had I actually noticed that on page 5 when I originally read it, that would have been my interpretation as well. Maybe it's worded poorly by SRP and the intent is just to imply that there will always be a grid charge applied, no matter how much you produce. Here's the summary from my April bill. While the excess solar production didn't amount to much, it did cover the small demand charge, taxes and 23 cents of the grid charge.

My 5.6 kW PV system is not necessarily oversized for my needs in the summer - there have been partially cloudy days where the 1 Powerwall barely made it through to 8pm with 0% reserve. In mid-late spring however, the net production exceeds my consumption, even with EV charging, since solar is almost optimal, panel and inverter efficiencies are high due to the relatively low temps, and the AC isn't running.

 

[D3xDt3Reaction]

Had I actually noticed that on page 5 when I originally read it, that would have been my interpretation as well. Maybe it's worded poorly by SRP and the intent is just to imply that there will always be a grid charge applied, no matter how much you produce. Here's the summary from my April bill. While the excess solar production didn't amount to much, it did cover the small demand charge, taxes and 23 cents of the grid charge.

View attachment 444034

My 5.6 kW PV system is not necessarily oversized for my needs in the summer - there have been partially cloudy days where the 1 Powerwall barely made it through to 8pm with 0% reserve. In mid-late spring however, the net production exceeds my consumption, even with EV charging, since solar is almost optimal, panel and inverter efficiencies are high due to the relatively low temps, and the AC isn't running.

I get where you’re coming from. 4 kW and 1 PW might be cutting it close for our house when it comes to demand mitigation on cloudy days. 8 kW and 2 PW might be overkill in cooler months since we have gas heating/dryer, so it would be nice to drop below $32. Simple payback on 8 kW and 2 PW could be <10 years if we can zero out demand charges, sell during peak, and buy during off peak.

 

[SOULPEDL]

Simple payback on 8 kW and 2 PW could be <10 years if we can zero out demand charges, sell during peak, and buy during off peak.

Is this true? I just ordered that exact system... 10 yrs, really?

Payment on that is $180/month for 20 yrs (after paying into it with your Fed tax rebate). My ave bill with SRP is $214/month. So with the monthly connection fee, I'm break even if I use zero power from SRP. So I think it's 20 yrs for me, not 10 yrs. If I had more efficient (everything), I'd maybe get away with just 1 PW. Then it's a steal because of the PW rebate from SRP. Even so, I look forward to not pre-chilling then sweating like I do now on EZ3, and making my own power! So worth it.

 

[D3xDt3Reaction]

Is this true? I just ordered that exact system... 10 yrs, really?

Payment on that is $180/month for 20 yrs (after paying into it with your Fed tax rebate). My ave bill with SRP is $214/month. So with the monthly connection fee, I'm break even if I use zero power from SRP. So I think it's 20 yrs for me, not 10 yrs. If I had more efficient (everything), I'd maybe get away with just 1 PW. Then it's a steal because of the PW rebate from SRP. Even so, I look forward to not pre-chilling then sweating like I do now on EZ3, and making my own power! So worth it.

If you pay cash, simple payback should be close to 10 not considering time value of money. Net cash outlay on 8 kW and 2 PW after federal tax credit and SRP battery rebate should be a little over $21k. If you can drop to $32 per month on average and save $182 per month, you would save $2100 per year or so.

 

[destructure00]

Anyone have solar and/or PW with APS? Trying to decide if I want to go that route....curious what the net effect has been on monthly bills. I see lots of talk about SRP but not much about APS.

 

[JayClark]

Thanks for confirming. You just moved my theory closer to practice, and it does make sense it would cost more energy (not $) to pre-chill. I'm calling this a scam that hurts our environment, and no longer just my opinion.

Not an expert here, but it seems the power companies basically have to scale/size their power production capacity to meet required peak production needs in their service areas no matter how little the community uses during off-peak periods. So one angle to consider is that by lowering peak requirements of our homes, and moving some of that load to off-peak via pre-cooling (even if overall usage goes up slightly) does actually help by lowering the total demand they have to support during peak usage (the "duck curve") with more dirty "peaker" plants, and lowering the overall required plant scale-up required to support those peaks as the population grows and we all start doubling and tripling our power usage by adding electric cars to our garages (at least during certain times of the year).

Having said that, I can also see the utilities are also protecting their business & profits to the detriment of the environment, by not actually encouraging consumers to "help" the peak load situation with some of there more punitive approaches to some of their plans and policies.

 

[SOULPEDL]

Correct, they are deferring power usage to even out demand and avoid infrastructure upgrades for real peak use. But there's another way. Let us make our own power but don't screw us with pennies to buy it back. Unfortunately, this type of fairness may limit growth potential for this privately held power company. The Tesla legal battle was likely for their survival, and I'm willing to pay for some of that infrastructure so I can trade power too.

But APS pays about 13 cents for the power their users generate, only 3 cents from SRP. How could the business models be so different? Does power during demand hours cost 13 cents or 3 cents? And why did Tesla bother to tangle legally for years with SRP and not APS as I understood it? All worth understanding further. I admit I'm lacking details myself so I'm more asking questions at this point. If anyone knows more...

I spoke to a Model 3 customer at the Tesla SC yesterday who was defending SRP (a friend he mentioned was affiliated with the power companies). His argument was that SRP was a power broker not a generator, and their costs to buy power are also very low. So why pay more from homeowners for what they can purchase on the open market? However, the discussion ended when I mentioned it was during peak periods and there's no way they pay 3 cents for peak power (maybe they can somehow???). So I contend they have a healthy profit during both times of day, demand or not. Thinking about it, the last mile of power delivery doesn't involve the open market from where they buy most of their power.

You're right that they are defending a business model (that is changing under their feet too) as any business would do. They are exploring options and using the PW rebate program to gather more data (what they claim). But like any business, things change and new models emerge. Problem is it's a monopoly in that I can't shop for cheaper power other than make my own. So I think my strategy will be to give back very little to SRP - hence 2 PWs in my system. I could add air conditioning to my garage so all my batteries last longer, or they could give me a better offer for my power that costs me 20+ cents per kWh on the "open" market.

So to your point @JayClark, pre-chilling is a valid method of shifting demand but it also wastes energy. A better way would be to partner with homeowners to use solar as a way to level demand (and maybe that's their plan). Their savings from infrastructure avoidance should be split more equally IMHO.

 

[D3xDt3Reaction]

But APS pays about 13 cents for the power their users generate, only 3 cents from SRP. How could the business models be so different? Does power during demand hours cost 13 cents or 3 cents?

Too bad arbitrage isn't feasible. We could buy power from SRP off peak and sell it to APS on peak.