Comments on 7.2kw system in San Diego

[solar pete]

Hi, just poped in and read the thread, looks like a nice tidy job, gotta say your roof's in the states look a bit different to what I'm used to, cheers

[ericf1]

Panels and Racking complete. Just a few loose ends to tie up tomorrow, then wait on the city and SDG&E.

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[ericf1]

Thanks Guys. Moving along pretty well.

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1 string of 12 panels up


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One roof penetration


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Inverter and new service panel. No surface/visible runs of conduit.


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Safety switch

Looks like the crew is on track to finish up late today or early tomorrow. Hopefully SDG&E will be ready tomorrow.

[russ]

Looking good!

[thejq]

Looks good. Good luck with the inspection tomorrow. SDG&E has a few TOU plans that you might to consider. I have a feeling that system will more than offset your usage.

[ericf1]

Installation is in progress! Ironridge XR100 racking on Ironridge Flashfoot footings is almost up. Solaredge SE7600 is mounted.

Major components of this installation are:
Ironridge XR100 Racking
SolarEdge se7600a-us002nnu2 Inverter
24 SolarEdge P300 Power Optimizers
24 LG300N1C-B3 Panels

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Each string will be a separate array of 12 panels, 3 high x 4 wide.

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Racking almost complete

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Facing due south, no shading issues.

Net metering request has been submitted and final inspection is expected tomorrow or Monday, depending on SDG&E and the city.

[sensij]

Obviously, SDG&E will throw some sand in the gears of my planning. Who knows what their end game will be? I know one option they want to pursue is significantly raising the tier 1 & 2 rates, while reducing the tier 3 & 4 rates. That puts a serious dent in the math of those who purchase small systems, using the current rates to justify.

Exactly. The increase in low tier rates helps improve the financial value of PV for those replacing low tier power, while the decrease in high tier rates will make it take longer than a buyer might have expected for their system to be net positive. The combined effect reduces the difference between replacing just high tier power, and replacing all power. Depending on what was paid, and what was pitched, some people with large systems might not come out ahead at all.

With a long enough time horizon, or good enough financing, or an expected increase in electricity consumption, or any number of other non-financial factors... sure, go big (personally, I am).

Sounds like you nailed the "good financing" piece.

The other important piece is if there are any improvements that would improve the energy efficiency and lower your consumption. Lowering consumption will always lower the bill, regardless of what SDG&E does.

[ericf1]

I'm going to be funding this system by replacing my current 30 yr mortgage (which will be paid off in 15 years at the rate I am currently paying it down) with a 15 year mortgage. Even with the PV system added to this mortgage, my new payment will be slightly cheaper. Payoff year will be the same, so I should be saving over $300/month. Obviously, most of the savings is in the refinance, but I'm looking at this as an overall financial move. It helps that the mortgage interest is tax deductible. Today, I save money and hopefully in 15 years I'll have no mortgage or power bill.

Obviously, SDG&E will throw some sand in the gears of my planning. Who knows what their end game will be? I know one option they want to pursue is significantly raising the tier 1 & 2 rates, while reducing the tier 3 & 4 rates. That puts a serious dent in the math of those who purchase small systems, using the current rates to justify.

My average electricity bill for the past 12 months was $290.00. The cost of adding $17.25K (system cost after tax credit) to the refinance is $120/mo (before considering mortgage deduction). While my savings might not be optimal, I thinks it's pretty good. Hopefully, SDG&E will not find a way to eat up all of my savings, though I know they will try.

As for over-sizing the system, I'm leaving a little room for system growth and increased energy use, as well as considering that the panels will degrade over time.

Eric

[sensij]

Not cut and dried indeed. Where do you get 500 kWh/yr. ?

Current min. is $.17/day. Also, the $10/mo. min. will kick in in a yr. or 2. hose are not charges for electricity.

I assumed the current 0.17 / day minimum charge for two years, and then $10 / mo minimum charge thereafter. There is some debate as the whether the $10 / mo will take the form of a fixed connection charge to be paid regardless, or a minimum charge. SDG&E wants it to be a fixed charge, in which case, go ahead and buy that last panel, because no matter how much you generate you'll be paying that fee. I'm sure some will argue with a straight face that you should buy even more panels in that case, and use the excess wholesale rates to cover the fixed fee, so that you can Stick it to SDG&E™.

Anyway, ORA wants it to be a minimum charge, in which case I believe that what I wrote above stands. Because it is an outcome with relevance, I'm making the assumption here that ORA wins this one. $10 / mo for 12 mo = $120. $120 / 0.24 per kWh = 500 kWh. 0.24 / kWh might be high, but not by much... ORA's testimony last month has the average low tier rate at about that level by 2020. If it is high, then 500 kWh is an underestimate.

Of course things won't occur exactly as I've assumed. It is just an illustrative case to show that 100% replacement may not always make sense.

Panel "markup", if I understand the meaning should be of no direct concern to a final buyer, more likely marginal system cost/Watt, or per panel,or some such #.

I said this: "smaller system should probably cost more per watt than a larger one". Maybe the reason why that statement is true is not a direct concern to a buyer, but for those interested, I offered the explanation, which involves panels costs and markups. I don't expect people to take anything I say as gospel, so I try to offer the justification for it. They can decide for themselves what directly concerns them.

[J.P.M.]

In San Diego, the case for sizing to cover 100% of usage is not cut and dried. If nothing else, the minimum monthly SDG&E charge means that you will be paying for 500 kWh of electricity annually anyway, which pretty much knocks out the last 300 W panel that would bring a system to 100%. Why pay for a panel if you will pay for the electricity either way? With no other considerations, paying cash for the next panel after that covering low tier usage that might take 10 years to recover at $3.50 / W, although good financing can help the payback quite a bit.

Complicating it further is the fact that a smaller system should probably cost more per watt than a larger one, since the marginal $ / W of a panel, even with mark-up, is still less than the $ / W of everything else. That means the benefits to going smaller aren't as strong as they would be if the system $ / W was fixed. Without an actual quote in hand for the larger and smaller system, it is tough to know how it shakes out, but part of the point is just the possibility that a smaller system might be better financially could motivate a quote request and some thought that wouldn't otherwise happen.

With a long enough time horizon, or good enough financing, or an expected increase in electricity consumption, or any number of other non-financial factors... sure, go big (personally, I am). If going solar is primarily a financial decision though, it can be worth the exercise of looking closely at system sizing and your own situation and see what might be right for you.

Not cut and dried indeed. Where do you get 500 kWh/yr. ?

Current min. is $.17/day. Also, the $10/mo. min. will kick in in a yr. or 2. hose are not charges for electricity. Panel "markup", if I understand the meaning should be of no direct concern to a final buyer, more likely marginal system cost/Watt, or per panel,or some such #.

Go as big as you want. Oversize by a factor of 2 or 3 or 10 if that's your choice. It's a free country. Glory in it and get what you feel is best for you. I'd only suggest know the landscape of the economics involved, learn something of the time value of money and use realistic assumptions. Also, know that CA rate reform will likely change a lot of assumptions and thus probably add a lot of uncertainty to what are already SWAGS about cost effectiveness and process economics.

On realistic assumptions: An example or two. Say you're 85 years old and a financial analysis says you need "X" # of years (and say X = 20 years) to make a 100% system "pay back" however you define it, and, say, a 70% system will pay back in "X-10" years, the smaller system may make more sense, especially if you have one foot in the grave and the other on a banana peel.

Or, if you fit something like the U.S. average, and you move every 6-8 yrs. or so, using an unrealistic discount rate, or unrealistic POCO rate increases (of the kind peddlers seem particularly fond of using as scare tactics and justification for unrealistically short paybacks or pie in the sky ROI's), or ?? to "force" a, say, 7 yr. payback may not be the most cost effective or honest with yourself thing to do, and may be the stuff of backing into a justification to conform to a decision already made that was based on ignorance, vendor hype and the easy way out of throwing money at a problem.

[sensij]

In San Diego, the case for sizing to cover 100% of usage is not cut and dried. If nothing else, the minimum monthly SDG&E charge means that you will be paying for 500 kWh of electricity annually anyway, which pretty much knocks out the last 300 W panel that would bring a system to 100%. Why pay for a panel if you will pay for the electricity either way? With no other considerations, paying cash for the next panel after that covering low tier usage that might take 10 years to recover at $3.50 / W, although good financing can help the payback quite a bit.

Complicating it further is the fact that a smaller system should probably cost more per watt than a larger one, since the marginal $ / W of a panel, even with mark-up, is still less than the $ / W of everything else. That means the benefits to going smaller aren't as strong as they would be if the system $ / W was fixed. Without an actual quote in hand for the larger and smaller system, it is tough to know how it shakes out, but part of the point is just the possibility that a smaller system might be better financially could motivate a quote request and some thought that wouldn't otherwise happen.

With a long enough time horizon, or good enough financing, or an expected increase in electricity consumption, or any number of other non-financial factors... sure, go big (personally, I am). If going solar is primarily a financial decision though, it can be worth the exercise of looking closely at system sizing and your own situation and see what might be right for you.

[silversaver]

That sounds like a kick a$$ setup. I picked SolarEdge with no shading either. You never know if a few leaves will fall on it, bird poop covering some part, or one panel degrades a little more than the rest. With a simple string inverter, all of the above can degrade your system performance. In fact the bigger (more panels) the system, the higher the probability of degradation due to these factors. Of course you can clean them once a while, but for most people, a while = never. With SolarEdge optimizer, only the panel with problem is affected. So yeah, I think you're wise to pick SolarEdge even without shading. The price sounds great too.

Personally I think a little over sizing is fine, because once you have solar, you tend to use little more. Or maybe when Model 3 comes out, you will want one.

+1

I heard of Solar Edge last year when I plan my solar. I think it has the advantage of ground level service just like the other string inverters + individual monitoring/optimizer (less heat vs Enphase). Too bad my installer only offers string inverter and I cannot say no to $2.84/Watt..... Not sure how durable those 300W LGs are, but I have been monitoring few systems in my area and they performed really well.

[thejq]

That sounds like a kick a$$ setup. I picked SolarEdge with no shading either. You never know if a few leaves will fall on it, bird poop covering some part, or one panel degrades a little more than the rest. With a simple string inverter, all of the above can degrade your system performance. In fact the bigger (more panels) the system, the higher the probability of degradation due to these factors. Of course you can clean them once a while, but for most people, a while = never. With SolarEdge optimizer, only the panel with problem is affected. So yeah, I think you're wise to pick SolarEdge even without shading. The price sounds great too.

Personally I think a little over sizing is fine, because once you have solar, you tend to use little more. Or maybe when Model 3 comes out, you will want one.

[sensij]

Your system looks very good to me. I too would be willing to pay a small premium for SolarEdge. One aspect that isn't mentioned much is that if you need to replace or add a panel for one reason or another, you don't have to worry about matching it electrically if you are using the optimizers. In a world where panels go obselete within a couple years, it seems like an inexpensive way to get a small degree of future-proofing.

The differences between the -B3 and -G3 are subtle. The -B3 is two-sided, although I doubt that is worth much in a rooftop installation. It guarantees slightly better year 1 max degradation (2% vs 3%). It stays more efficient in cloud cover (2% efficiency reduction at 200 W/m2 vs 4.5% reduction). It might perform slightly better at elevated temperature. SAM and SolarEdge's design tools don't have the -B3 listed yet, SMA's tool does but actually pegs the -G3 as producing slightly more (0.4%) in year 0 if everything else is kept constant.

TL;DR... I'd pick the -B3 if they were the same price, but the -G3 looks fine.

In general, I'd be looking for value in the 270 W range, but at the price you've been quoted, I wouldn't count on getting it much lower. It sounds like you've already done plenty of shopping. J.P.M.'s point to consider a smaller system that replaces only high tier consumption is a worthwhile exercise. Even if it doesn't change anything you are doing, it helps highlight the time-dependent nature of the payback, and the trades between rate of return and lifetime total return that can be made to financially optimize over a time period of interest.

[silversaver]

The solar system should have cover 100% of your usage. The SAM shows about 12,443kWh base on SD. I hope you get a good deal $/W. If you plan on living little more comfortable during Summar and thinking of adding an EV then I think it is a really good size. Of course if you want to save the money, conserve energy and count every penny worth, then go with smaller system. A 6kW will do the job. The weather of Socal will slowly raise and IMO the electricity demand will be increasing every year.....