Calculating savings on existing solar lease/PPA

Depends on the situation and what the person paying the bills thinks is a plus. Opinions and situations vary.

I live in an HOA w/~ 550 single family homes. Of those, ~ 150 have added PV since 2006. For several reasons, I'm pretty familiar with all of them, from proposal, pricing, vendor, size, estimated production and approx. annual savings and other things. All of the 150 got PV to reduce electric bills. All paid lip service to saving the environment and little more. All of the 150 would have been better off with preliminary conservation efforts. Few made any. For reasons having mostly to do with solar ignorance, most systems in this HOA are oversized and so less than optimally or even reasonably close to being marginally cost effective except for those folks whose use is so high that they can't get a big enough system on their property. Perhaps Ironically, those folks tend to have the more cost effective systems if the ignorance of no conservation before PV ignored.

I can only speak to my experiences and what I read and the opinions I form, but I am of the opinion that the situation, knowledgeability and attitudes of residents in my HOA about residential energy use and PV's potential to cost effectively deal with what are mostly self inflicted high electric bills is pretty typical. And pretty abysmal.

Well...I look at a power plant on my roof this way: What do you have to show after you pay your POCO crazy tier prices for 10 years? NADA!
All you are doing is diverting that money you would have spent anyway into something that actually is going to give you decades of free power.

Well that's one way to look at it. But as a possible answer to what looks like a rhetorical question: One thing you have to show for paying for all that electricity is that you're alive and living the lifestyle allowed by having electricity in your life. Think of what your lifestyle would be like without electricity (or remember the feeling you had 5 minutes or more into the last time your power went out) and consider the electric bills to be the cost of a pretty cushy existence. I know I do.

The following addresses financial considerations only. I appreciate that life is a lot more than money and lots of things go into lifestyle choices, but it seems that PV is mostly a financial choice and so that's what this post is all about.

One way some folks might look at a power plant on their property (before they make the investment) is to try to reasonably (and effectively) guess at two scenarios: one with PV and one without PV and see where their financial state might be in 10 or 15 yrs., more or less, under each scenario. The deal is to see which scenario puts (or leaves) more money in your pocket at the end of the term.

To oversimplify, a zero up front cost PV system (say it's free) will always be cost effective. At the end of the term of 10 yrs. or whatever, the net value of the savings by having the free system will be the net value of the electricity the system generated.

If the same system were to cost, say, 1 million dollars, it probably won't be cost effective on any residence.

In between, there is a system cost and size where the net present value of the savings in electric bills over the time period under consideration just matches the net present value of the initial cost of the system plus the net present value of the maint. cost less the net present value of the salvage value of the system (~ = how the system affects home resale value) + other things like tax considerations, inflation, cost of money if financed, etc.

That analysis can be as involved or as simple as the person paying the bills thinks is appropriate. In general, the more savvy, informed and knowledgeable the analyst is, the higher is the probability of getting a cost effective system.

If the system cost as calculated is greater than the calculated (and probably estimated) savings, then, under the assumptions used, you'll be money ahead not getting the system as designed, or changing the design. If the opposite outcome of the analysis is obtained, then system acquisition will be more cost effective than not acquiring the system.

If the system as proposed is marginally cost effective, the next step is to optimize the system to maximize the long term savings. That usually involves further analysis often including seeing what happens to cost/savings when system sizes or material are varied and most likely requotes from installers and or suppliers. That most folks don't take it that far is a matter of choice, but that says nothing about the validity of being more thorough.

Another, and useful additional consideration, with respect to financial considerations only, and assuming a cost effective system is possible, is to look at any (financially) optimally designed system cost and see what other places for investment might be possible given your risk tolerance that might be more cost effective. That comes under the a broad heading of something often called comparison of alternatives analysis. So, if an alternative investment is available for your risk tolerance that puts (or leaves) more $$ in your pocket at the end of the period under consideration, that investment is the one to choose over the PV.

Ok, that was a lot to take in but you really overcomplicated it all.
If you buy a car, it's a cost and it does give you benefit but it does not really pay you back in a strict sense.
PV on the other hand, does when purchased.
Of course cost matters and even in the case of my SP system which is not a cheap one, the long term payback is huge.
If it were not, it would not be worth the risk.

Well, complication is a matter of opinion. Hell, I was just getting warmed up. Maybe it was more complicated than you would like to see or think about. I consider what I wrote part of what might be necessary when making an informed decision about what can be a major financial and something of a lifestyle changing event.

As I often write, opinions vary. Take what you want. Scrap the rest.

FWIW, I too have a S.P. system. When acquired, according to the CSI database, it was the 2d least expensive S.P. system installed in CA up to that time (reservation # SD - CSI - 17646). The least expensive system per STC watt system at that time (and, I believe still is) was done by a S.P. vendor, Stellar Solar if my memory serves me correctly, on his own residence.

Hard as I tried, and making it as cost effective as possible in terms of size and vendor quality as I could, I couldn't make my system, as designed by me and to my requirements, cost effective under any of my life cycle cost inputs. But I knew that would probably be the case walking in.

Maybe I've got more time to spend than money and more money than brains, but I didn't do turnkey PV for cost effectiveness. If cost effectiveness was the major criterion, I'd maybe just now consider PV (and maybe not, given the way NEM has changed in my area for current installs that reduced PV cost effectiveness by ~ 23 - 25 %).

That is, when designed and contracted, I was pretty sure that with my equipment and vendor choices, and my chosen system lifecycle of 12 years and other financial requirements, I'd have a lower probability of being financially better off with the PV system I designed than if I'd used the assets for other things that would provide a greater ROI over the same time.

I didn't get the PV solely as a financial decision any more than any other pastime/hobby I engage in is done primarily for financial gain. But, that's just me.

Lol..I guess you were just getting warmed up.
I admit too that it's not all about the financials making sense (unless CA really messes with us).
I do think it is a cool hobby and fun to just monitor and understand the tech behind it as I see you seem to.
I have to admit I don't get why your PV system wouldn't be cost effective since you seem to have really done your homework?

Lots of reasons. Three of the bigger ones:

1.) The longer the time frame for a serious cost analysis, the easier it becomes to make any system cost effective. Most peddlers use 20 or more years. As an opinion, Even though systems last a long time, because in the U.S. most homeowners move, on average about every 7 - 10 yrs. or so, I don't think that 20 yrs. is a useful or representative number for a valid cost analysis for many potential PV owners.

2.) I use a 12 yr. time frame, mostly because I expect in a few more years age dementia will have me in the happy land of padded cells playing fungo with my poop. Also, in 2013 when I designed the array, I expected 12 yrs. or so hence that technology, as well as more marketing hype would make my stuff apparently or actually obsolete and I wanted a fair assessment of how bad I was taking it in the shorts by doing what I did. I expect the stuff to be working for a long time, but how I did what I did will probably not be cost effective.

3.) I have a Sunpower system. They are less cost effective than other systems built using equipment of equal quality that are equally fit for purpose. I paid a negotiated price of $4.50/STC W in 2013 and got the 2d lowest price of any residential S.P. in CA up to that time. I could have got an LG system for a negotiated $3.68/STC Watt and have as good a system. That LG system, at that time would have been marginally cost effective for me under my assumptions after ~ 13.5 yrs.

I got the Sunpower system to put my money where my mouth is and to satisfy my own curiosity.

You haven't been here long enough to have seen a lot of my major rantings about Sunpower in the past. Precis: Good stuff, but way overpriced - like buying a Mercedes or a Lexus as a grocery hauler when a Ford or Toyota will be as fit for purpose. I got, and still get, a lot of blowback on that from folks who drank the S.P. koolaid, and effectively screwed themselves by overpaying for S.P. when other equally fit for purpose and equally durable stuff could be had for ~ 20-30% less. Bottom line: I overpaid for good stuff to verify for myself by owning a well designed and well installed Sunpower system whether or not Sunpower's claims of "highest efficiency" and greater production were true or not.

I believe after close to 6 years of very close monitoring of my system's input and output, and monitoring about 6 systems non Sunpower systems owned by cooperating neighbors, plus looking at a lot of output of PVOutput systems in my area, I can say that IMO, while Sunpower stuff is good, it's no better or more fit for purpose than other quality equipment. It simply costs more. The output of my Sunpower system and other Sunpwer systems per installed STC W is no more than other PV systems in my area that use non Sunpower equipment.

I don't think or feel that I could make that claim if I'd gotten a non Sunpower system. I chalk off the extra cost as part of the cost of learning. More time than money and more money than brains.

Solar is less than a profession but more than a hobby for me. It was the original impetus that made me return to school and switch career paths to engineering. I was once a commission based sales rep. (peddler) of industrial power and process equipment. I was kind of bored and then got the solar bug as a means to help stay warm while not going broke doing so in Buffalo, NY. So, I redegreed and reemployed. Since no one in the Buffalo area (in the late '70's) was building solar equipment, I employed, worked and got licensed as a mechanical engineer designing industrial power generation and process equipment, some of it similar to some of the stuff I once peddled.

Part of both careers, sales and engineering, involved justifying equipment costs - either to potential customers or, later, to my company's bosses - and/or evaluating cost effectiveness of various methods of process design, often to folks who knew a lot more about cost analysis than I did. If I know a bit about cost analysis, that's where it got started. Solar process economics has and uses a lot of the same methods of cost analysis, life cycle costing and time value of money methods as those needed and used to justify or examine buying and budget decisions in an industrial environment. All that is part and parcel of what engineers often call engineering economics.

Take what you want of the above. scrap the rest.

Thanks for the perspective, good stuff.
When I buy a car, I go Honda because they have earned that place.
So far, Sunpower is not impressing me either and yes, I paid for it but that Ca rebate does ease the pain somewhat.
I would go Panasonic, LG most likely too but out of 4 bids, only the SP option could meet my needs at the time.

You're welcome.

I'm not suggesting anything other than that Sunpower stuff, while good, is no more fit for purpose than other stuff of equal quality and reliability that can be had for a significantly lower initial cost and what's probably about the same operating and maint. cost and PITA factors.

Pay your money, take your choice and hail the freedom to make free choices, even cost ineffective ones.

Al I'm suggesting/writing is that while not every decision ought to hinge solely on financial criteria, for those that do, or where financial considerations are important, a little self education can be very profitable for a small investment of time and brainpower.

On the CA rebates: At the time I signed (08/14/2013), the CA rebate was @ $0.20/CSI calculated W for any system. In effect, that meant an LG system at $3.68/STC W got a higher %age rebate than a Sunpower system at $4.50/ STC W, or a better ROI for the initial investment. That is, to a first approx., $0.2/$3.68 > $0.20/$4.50. If rebates are calculated on the same per W basis, lower cost systems will show a greater ROI with respect to such rebates.

On the vehicle analogy, I bought a Toyota V6 Venza in 2010. Still a daily driver. I could have bought a Lexus RX 350 (same V6), paid about $10K more and got better leather and some real wood instead of the adequate but less supple leather and fake wood in the Venza. Other than that, the vehicles are pretty much the same. I think the Lexus warranty is 1 yr. longer, but nothing went wrong w/ the Venza until last spring when the alternator crapped the bed. I've got a sound pressure level meter. I used it during my test drives when comparing the noise in both vehicles under same conditions, speeds and roads. As I recall, the sound levels were within a couple of DB(a) +/- for similar/same drives for both vehicles. The ride quality is about the same IMO. Engines are identical. More FWIW, acceleration seemed just a tad better w/more passing grunt w/the Venza.

That experience seems to be analogous to my opinions about solar panels, their quality and suitability as an appliance.

Hmm...I don't see the math clearly then.
If you are getting a 30% tax rebate for any PV setup, a more expensive system would get a higher return.
Maybe I just need more coffee?

I guess I should clarify that tax benefits can sway a more expensive PV system but is it really worth it...maybe, maybe not.

A system, like most anything else, is worth no more to any individual than they are willing to pay for it. The more informed and knowledgeable one is about how and when they use electricity, how PV works, including its limitations, and solar process economics, the greater the probability they won't get screwed by their own ignorance.

Yes, I really was surprised at what I started to learn about usage, the path of the sun and things you just don't usually think about otherwise.