Feedback on Quotes - Phoenix AZ

[Volusiano]

I do basicly the same down to pretty much just getting the monthly data for my spreadsheets. I've lived with PV systems for 5 years and the novelty of daily monitoring and analyses wears off quickly over time. I wouldn't pay very much extra for monitoring equipment. I have an Aurora Power-One inverter and use the Aurora Communicator software on a PC for inverter data which I look at occasionally for curiosity sake mostly - especially like the next 3 days with the cooler temps, wind, and clear skies - I might set a daily production record.

Haha, great minds think alike. The interest stuff to me, beside the monthly tallies, is to wait until May, which is the typical highest production month of the year, to see how close I can get to my system's DC KW name plate rating. Of course it'll never be 100%. But I use 0.874 for my DC to AC derating factor, so I'm very curious to see how close I can get to this derating factor.

With my 11 KW system and the derating factor of 0.874, I'm supposed to get a peak of 9.6 KW AC from my system. So far (I've only had my system installed since last Oct'13), 4/29/2014 has been the highest production day for me, and I had a peak of 8.9 at 1pm on 4/29/2014. That's still 8% shy of my theoretical 9.6 kw AC peak. But it's not too shabby.

[Volusiano]

You may not have as much data from APS as SRP provides but at least you have a significantly better net metering tariff. I'd trade more data any day for APS's net metering tariff. I think the solar industry won the latest round with APS and the Commission. But eventually, I think net metering has to change (even for the currently grandfathered APS solar customers). If SRP had the same net metering as APS, my savings from PV would increase by about 10%. Of course full disclosure requires that I'm likely saving a good portion of that 10% by the lower SRP rates.

Can you elaborate some more on what this better net metering tariff entails? I have no idea what it is. The only main difference I know about is that APS trues up at the end of the calendar year, while SRP trues up net metering in April (less advantage for customers). And of course the recent solar fee approval for new solar accounts with APS.

[Volusiano]

LOL, yep I retired early at 56 and been living the "dream" for nearly 11 years now.

I'm jealous. Wish I can retire at 56...

[+3 Golfer]

Can you elaborate some more on what this better net metering tariff entails? I have no idea what it is. The only main difference I know about is that APS trues up at the end of the calendar year, while SRP trues up net metering in April (less advantage for customers). And of course the recent solar fee approval for new solar accounts with APS.

Yes, the true up means everything if one is trying to get the maximum return from solar. By truing up in Dec., one can starting banking excess winter generation for use in the summer after their Dec. meter reading. So, one is shifting PV generation from a low usage period to high usage periods. Under SRP all this winter period excess generation that now starts in say Oct. is banked until one's April meter reading before one's high usage period begins. So, under SRP one starts the high usage period with little banked energy. SRP pays about $0.03 per kWh which is the average Palo Verde trading hub on-peak, firm price. Last, I knew APS was paying $0.06 - $0.07 per kWh.

Let's use a simple example where the PV generation and loads are the same:

1) Assume under APS the true up is 300 kWh at $0.07 / kWh = $21
2) Assume that under SRP the true up is the 300 kWh plus another 1000 kWh or 1300 kWh at $0.03 = $39.
3) But under APS one has 1000 kWh to use during the summer peak period.
4) Depending on the rate schedule, let's assume the 1000 kWh is used such that the average cost of the kWh avoided is $0.12 / kWh which equals $120.

So, under APS one saves $120 + $21 = $141 while under SRP one only saves $39. That's about $100 a year difference primarily from the ability to use excess energy carried over from low demand periods into high demand / cost periods. Of course real world conditions could be higher or lower but the point remains the same.

[Ian S]

Last, I knew APS was paying $0.06 - $0.07 per kWh.

They reduced it last year to $0.029/kWh. Still, I would agree that the December trueup is a significant advantage. So far, I have over 1,000 kWh peak banked for this year.

[Volusiano]

Yes, the true up means everything if one is trying to get the maximum return from solar. By truing up in Dec., one can starting banking excess winter generation for use in the summer after their Dec. meter reading. So, one is shifting PV generation from a low usage period to high usage periods. Under SRP all this winter period excess generation that now starts in say Oct. is banked until one's April meter reading before one's high usage period begins. So, under SRP one starts the high usage period with little banked energy. SRP pays about $0.03 per kWh which is the average Palo Verde trading hub on-peak, non-firm price. Last, I knew APS was paying $0.06 - $0.07 per kWh.

Let's use a simple example where the PV generation and loads are the same:

1) Assume under APS the true up is 300 kWh at $0.07 / kWh = $21
2) Assume that under SRP the true up is the 300 kWh plus another 1000 kWh or 1300 kWh at $0.03 = $39.
3) But under APS one has 1000 kWh to use during the summer peak period.
4) Depending on the rate schedule, let's assume the 1000 kWh is used such that the average cost of the kWh avoided is $0.12 / kWh which equals $120.

So, under APS one saves $120 + $21 = $141 while under SRP one only saves $39. That's about $100 a year difference primarily from the ability to use excess energy carried over from low demand periods into high demand / cost periods. Of course real world conditions could be higher or lower but the point remains the same.

Sure, I understand the difference the true up timing makes. In my case, I built up an excess of over 1.1 KW at the April true up time that basically goes to waste, while I could have carried it over into the summer time.

When you said net metering tariff, I thought you meant something else other than the true up. But if it's just the true up, then OK, I get it.

[fd3s1994]

Out of all the companies that I've spoken to so far, only one person brought this up. Your explanation and breakdown makes it very easy to understand and corresponds to the documentation that SRP has on their web site. What I'm not 100% clear on is the what SRP would do, if you don't request a check from them when they true up at the end of their fiscal year (end of April). Is it just credited to your account in terms of dollars? I would imagine so, but it's not explicitly stated so.

Thanks for all the pointers and good information. I know the ACPVs do command a premium over DC panels and that's not surprising, but I looked at the retail cost of the SolarEdge optimizer and they were going for about $80 a pop, retail. I'm sure there's some labor and interconnect and hardware costs that will need to be built in as well.

I'm going to get a few more quotes on similar panels without the microinverter or optimizer and see where we land.

Thanks.

[Volusiano]

One misconception that I had initially was that there'd be only 1 bucket for credits and you get more credits for the peak hours production (I think some CA POCOs do that). But it was clarified to me very soon that the on-peak and off-peak credits are kept in separate buckets and used accordingly in AZ. So that's not as advantageous compared to sharing a single bucket of credits only.

[Volusiano]

One other comment about the SRP April true up which I learned recently is that it's not at the end of the month, but instead at the end of your April billing cycle, which may be earlier in the month. So don't go crazy and try to burn up your credits through the whole month of April.

[fd3s1994]

Sure, I understand the difference the true up timing makes. In my case, I built up an excess of over 1.1 KW at the April true up time that basically goes to waste, while I could have carried it over into the summer time.

When you said net metering tariff, I thought you meant something else other than the true up. But if it's just the true up, then OK, I get it.

When you talk about the TOU, it would affect panel owners in that you want to produce as much power as you can during that period to offset costs? We get a flat rate for excess energy produced regardless of plan or when the excess power was generated?

Thanks.

[Volusiano]

When you talk about the TOU, it would affect panel owners in that you want to produce as much power as you can during that period to offset costs? We get a flat rate for excess energy produced regardless of plan or when the excess power was generated?

You don't really get a "rate of energy" for excess production. Remember if you're on TOU, there are 2 buckets (on-peak and off-peak), and the excess for on-peak just goes to the on-peak bucket and vice versa. If you over run your on-peak time at the end of your billing cycle, you can't withdraw credits from the off-peak bucket to compensate. You'll just have to pay for the overage at whatever premium rate your on-peak time is. And vice versa for off-peak. If you under-run, then the excess credit rolls over to next month until the true up month. So from that perspective, you want to watch each bucket individually and if one bucket is fuller than the other bucket, then you may want to shift your usage load to use up more of the fuller bucket. For example, if your on-peak bucket is fuller, you may want to start doing laundry or schedule your pool pump during on-peak more to use up credits in the on-peak bucket.

Or, you can say my on-peak bucket has a lot of value and since my true-up is not until April (if you're SRP), I'll just let the credits in there roll over from month to month and if I have excess into the winter time, I'll use it for heating during my on-peak. This is actually my strategy because I don't have natural gas in my subdivision, so excess on-peak credits comes in handy for electric heating in the winter time for me. Also, SRP on-peak in the winter time is 5-9am and 5-9 pm, when I need electric heating the most. So it's a useful strategy for me.

Your choice of going with TOU or not depends on your system size, too. If you size it so you'd get net zero metering on the average (size to meet demand), then you'd want to be on the basic plan only because now the cost of energy is no longer relevant to you. It can be $10/kwh or $0.10/kwh and the end result is the same to you. So by staying on the basic plan, you only have 1 bucket of credits to share and that makes it easier to manage. Also, you have more flexibility in the placement of your panels to maximize production. For example, if you have east/west roof, you'd probably want the panels on the east roof for better production since the panels will operate cooler in the morning for better efficiency.

On the other hand, if your system size is smaller than your demand, then there's value in going with a TOU plan. And now placement matters because you want to maximize production during your peak time to meet up with peak time demand, which commands a premium rate. So if you have an east/west roof, the better placement in this case would be on the west roof. If you have north/south facing roof, then the south roof is a no-brainer either way.

It's probably also better in this case to go with the 1-8pm peak TOU (or noon-7pm in APS's case) instead of the 3-6pm or 4-7pm EZ3 because the top of your production bell curve is going to be around 1pm or so, right around when on-peak time starts. If you go with the 3-6pm or 4-7pm plan, your production will be considerably less during this time, which may not be enough to meet your demand during this period, causing you to pay some premium $ if you over run. And 3-6/4-7 premium is considerably higher than 1-8pm premium also.

[fd3s1994]

You don't really get a "rate of energy" for excess production. Remember if you're on TOU, there are 2 buckets (on-peak and off-peak), and the excess for on-peak just goes to the on-peak bucket and vice versa. If you over run your on-peak time at the end of your billing cycle, you can't withdraw credits from the off-peak bucket to compensate. You'll just have to pay for the overage at whatever premium rate your on-peak time is. And vice versa for off-peak. If you under-run, then the excess credit rolls over to next month until the true up month. So from that perspective, you want to watch each bucket individually and if one bucket is fuller than the other bucket, then you may want to shift your usage load to use up more of the fuller bucket. For example, if your on-peak bucket is fuller, you may want to start doing laundry or schedule your pool pump during on-peak more to use up credits in the on-peak bucket.

Or, you can say my on-peak bucket has a lot of value and since my true-up is not until April (if you're SRP), I'll just let the credits in there roll over from month to month and if I have excess into the winter time, I'll use it for heating during my on-peak. This is actually my strategy because I don't have natural gas in my subdivision, so excess on-peak credits comes in handy for electric heating in the winter time for me. Also, SRP on-peak in the winter time is 5-9am and 5-9 pm, when I need electric heating the most. So it's a useful strategy for me.

Your choice of going with TOU or not depends on your system size, too. If you size it so you'd get net zero metering on the average (size to meet demand), then you'd want to be on the basic plan only because now the cost of energy is no longer relevant to you. It can be $10/kwh or $0.10/kwh and the end result is the same to you. So by staying on the basic plan, you only have 1 bucket of credits to share and that makes it easier to manage. Also, you have more flexibility in the placement of your panels to maximize production. For example, if you have east/west roof, you'd probably want the panels on the east roof for better production since the panels will operate cooler in the morning for better efficiency.

On the other hand, if your system size is smaller than your demand, then there's value in going with a TOU plan. And now placement matters because you want to maximize production during your peak time to meet up with peak time demand. So if you have an east/west roof, the better placement in this case would be on the west roof. If you have north/south facing roof, then the south roof is a no-brainer either way.

It's probably also better in this case to go with the 1-8pm peak TOU (or noon-7pm in APS's case) instead of the 3-6pm or 4-7pm EZ3 because your the top of your production bell curve is going to be around 1pm or so, right around when on-peak time starts. If you go with the 3-6pm or 4-7pm plan, your production will be considerably less during this time, which may not be enough to meet your demand during this period, causing you to pay some premium $ if you over run. And 3-6/4-7 premium is considerably higher than 1-8pm premium also.

This makes sense. It wasn't entirely clear to me on what would be considered peak, but it makes sense that it is related to the plan that you pick, We're on the EZ3 (3-6) right now because it makes the most sense for our activity pattern. I would think that the 1-8 TOU or the standard (depending on system sizing). Hopefully, the vendors will also help us confirm this with their tools and spreadsheets.

Thanks for taking the time to help clarify this.

[Ian S]

Your choice of going with TOU or not depends on your system size, too. If you size it so you'd get net zero metering on the average (size to meet demand), then you'd want to be on the basic plan only because now the cost of energy is no longer relevant to you. It can be $10/kwh or $0.10/kwh and the end result is the same to you.

I've wondered about this and think in many cases, especially with SRP and its April trueup, that it won't work quite that well. With gas for heating, my electric usage varies greatly throughout the year: I typically use more than 4X the electricity in the summer months as I do in January through March for example. In contrast, my solar production only varies by a factor of <2X so if I size the system to meet 100% of annual needs, my summer months will still yield significant bills while my overage at true-up gets minimal compensation. Am I missing something?

[Volusiano]

I've wondered about this and think in many cases, especially with SRP and its April trueup, that it won't work quite that well. With gas for heating, my electric usage varies greatly throughout the year: I typically use more than 4X the electricity in the summer months as I do in January through March for example. In contrast, my solar production only varies by a factor of <2X so if I size the system to meet 100% of annual needs, my summer months will still yield significant bills while my overage at true-up gets minimal compensation. Am I missing something?

No, you're not missing anything, Ian.

If you size your system based on the annual usage, especially with the April true-up, then it may not work out correctly, just like you said.

If you size your system based on the highest demand month, then you're probably going to oversize.

But you can just lay it all out on a spreadsheet to size it such that you won't have any overage in the summer but also won't have too much excess by your true-up month. That's the beauty of cranking the numbers through a spreadsheet. One column would be the PV Watts production estimate by month. The other column is your monthly demand based on past data. Starting from your true-up month, the diff of these 2 each month will be the roll-over credits. Size your system such that any of your summer monthly production is equal to or greater than the corresponding monthly demand + any roll-over credits for that month, and it should be close enough.

You may have to go through a few rounds of PV Watts estimates for slightly different sized systems, but that's no big deal.

If you tune it to not be under water for the summer months, it may be a little over sized for the winter months. Then you can dial it back a little to be underwater the last month of summer, as long as the premium you pay for the summer month's overage can be recouped by the true up $ in the end, then you've achieved net zero.

[+3 Golfer]

This makes sense. It wasn't entirely clear to me on what would be considered peak, but it makes sense that it is related to the plan that you pick, We're on the EZ3 (3-6) right now because it makes the most sense for our activity pattern. I would think that the 1-8 TOU or the standard (depending on system sizing). Hopefully, the vendors will also help us confirm this with their tools and spreadsheets.

Thanks for taking the time to help clarify this.

I have yet to see a vendor that has a sophisticated spreadsheet that can do such. The vendor will always try to sell you more than you need and will underestimate production by using conservative assumptions. They don't want to be put in a position of underperforming on their estimates. They will generally use an average blended utility energy rate.

I developed my own spreadsheets for each rate schedule when I analyzed my APS connected system and modified them for SRP's standard, EZ3, and TOU tariffs and then run what if scenarios varying load and generation and so forth. I also model shifting certain loads like pool pump, water heating, and AC. I then look at what size system gives the best return. Generally, if one produces more energy than one's load on an annual basis, return goes down. EZ3 wins for me because I can easily shift pool and water heating load into the EZ3 on - peak period so that each billing cycle nets to zero on-peak load for the May through Sept higher load periods. I chose the 2pm-5pm period as the most advantageous for me. During the Oct- April period, I can simply leave the water heating and pool pump load in the EZ3 period and bank very little on-peak since there is no AC load.

To get the standard tariff to win one has to generally install a larger system than one's energy usage. The reason is that under TOU or EZ3 one can take advantage of lower off-peak rates and by lowering on-peak usage with PV generation. Last year every month of my on-peak net energy was zero.

The issue with the TOU is the on-peak period extends to 8pm in the summer months and there's little PV generation in the early evening. Depending on AC load and other loads, one might have to put in a larger system than needed or curtail load to get net energy during this on-peak period to zero. The problem with the winter period on-peak period (5am-9am and 5 pm - 9 pm), there is virtually no PV generation in that period. So one ends up buying on-peak energy (albeit not very expensive) and banks a lot more off-peak energy than under EZ3. But because of the rate structure one can get their savings under TOU and EZ3 to be virtually the same for the same size system. IMO, it's harder to manage load under TOU than EZ3.

I found that covering about 90% of my load with PV gives the best return. Now there may be price break points where going slightly large or smaller offers a lower cost/kW installed cost. Also, remember my point on the vendors forecast of generation. My models always show about 6-10% more PV generation than the vendor's model. On my current system, June 10th will be the one year anniversary. Right now SRP's generation meter show 7920 kWh. Between now and June 10th (34 days), I should be around 9000 kWh. Vendors showed around 8400 kWh of generation. My usage since June 10th, 2013 is 8489 kWh. I'm hedging 93% of my load with PV.

The problem with oversizing a system is the amount of excess energy that will be banked and purchased at a very low rate. For example, to pay off the monthly billing charge of $18.14 at $0.03 / kWh, requires 600 kWh of excess generation or 7200 kWh per year (about 3.6 kW of installed capacity). That may be sufficient to zero out net energy each month also but one needs to run models. So, one will end up paying nothing to the utility under their current tariffs. But the likely cost of 3.6 additional kW of solar capacity will drag down the overall PV system return.

So, bottom line is that if the 1st system meets at least 90% of your load, it is the cheapest $/kW and will likely give the best return.