I think we're going solar

Very good, I just wanted to make sure you had done due diligence. Sounds like you most definitely have
Many people are dismissive of solar in northern latitudes. That alone though, is not a reason to dismiss solar.
In Minneapolis, solar works as well as it does in Miami.

 

These estimates must include local weather history, and should include adjustments for any tree shade interference, so should be specific to a particular location. That is why Jerry is projected to get 1.46kWh/W of annual production, but you get just 1.15, Salamander is projected to get 1.0, and I get a measly 0.89 due to Seattle-area winter cloudcover and several neighbors' trees.

But I did it anyway, to put my money where my mouth is. It is well on track to paying back, it will just take longer than for folks with more favorable conditions.

Do beware the specialness of the quoted timeframes. E.g. shift them to 21 and 13 years, and the annualized rates become dramatically different. Every now and then, we get decade-long timeframes where the indexes mostly just tread water, and those 8% expectations turn into a pipedream.

A problem with these simple ROI calculations is that they completely ignore one's contribution towards addressing AGW / CC.

 

Jerry - Congrats on things working out for you so well. I think you're going to be thrilled with the new roof and panels once everything is installed and working.

I'd have to pull out the details on our solar system but we've been extremely happy with it. Living in the desert southwest means lots of sunlight. We were limited as to what we could originally install because the energy companies were faced with the dilemma of being forced to buy the excess energy at a rate higher than what they could purchase elsewhere. The amount allowed was based on the average home of this size in this area. We don't have a hot tub or pool, keep the thermostat at 80*F in the summer, replaced every bulb in the place with LEDs, have a gas water heater, stove and furnace, etc. so we knew we were already going to be banking energy at the amount they allowed.

We just completed our first year with the system. Starting in January, we hadn't banked enough to totally offset the 115*F heat of August so our bill went up to a whopping $35. Other than that we've been paying $3-$13 a month to be hooked up to the grid. Adding October through January to this year's winter's bank should mean we won't see a bill over $13-20 for the foreseeable future. Beats the heck out of our neighbors and their $300-500 summer electric bills.

We can add panels at our own expense now should we decide to put in a hot tub, pool, sauna, etc. We just won't be able to claim the government credits. We're perfectly ok with that.

 

Yeah, I really wanted the solar to work in our favor, but at the current price, it is still too expensive. Looking back and comparing past quotes, in just three years, the cost of PV installation dropped from $3.7/watt to $2.5/watt. I am waiting for the cost to hit $1/watt. Alternatively, I may invest less money in a smaller system and DIY install to bring the upfront cost low.

Yes, to that end, I have been paying extra fees to the utility to get 100% renewable energy source, and I have signed up for the community solar which is to become operational sometime later this year. The community solar project share is easy and saves money (15% discount on utility bill) and no upfront money or installation of PV panel on my roof.

I am not so sure about the dramatically different rate of returns over the span of 10 years. Yes, there have been some years of low or negative productivity, most recently in the 2008-2009 financial crisis which is your comment of 13 years ago, but overall the market has performed better prior to that crush especially at your comment of 20 years ago (2000-2001) which IIRC is the period of .com bubble burst.

 

That does make for a bulletproof excuse.

I haven't used that estimator. Back in my day, I did use an old NREL estimator, since replaced by an updated version.

Do note that those Enphase IQ7 inverters have a maximum continuous output of just 240 VA (or 250 peak), so will be clipping under peak conditions (max sun at solar noon on crystal clear cool late spring days). The IQ7Plus models can put out 290 VA, so will clip less often. This is a normal equipment cost tradeoff (do you want to put your last dollars into paying for bigger inverters to handle the rare peak power of the panels, or put that money into more silicon for greater collection during more common non-peak conditions?). I hope that the estimating package takes separate inputs for the inverter capacity and the panel's rated output, so that the tradeoff can be properly quantified.

I have older Enphase microinverters (M215 on first and second phases, M250 on the third), and have been very happy with them. The panels were in the 265-285W range, each phase different based on then-available pricing and supply.

Supposedly, my excess not used within a year reverts to the public utility as a free gift to them, but their billing system has been changing and remains somewhat under featured and opaque, not (yet) showing how much net metering credit is banked. I won't be getting better detail unless or until dropping below net-zero, which hopefully won't happen until acquiring a plug-in car. Which will be my excuse to add a few more panels.

I intentionally aimed for a bit of excess capacity to cover panel aging, tree growth, weather variations, and some minor load growth or less diligent conservation without breaking below net-zero and losing bragging rights. Folks aiming for maximum payback should aim a bit lower to reduce the 'wastage' of having to give away some free or below-cost energy.

 

I'm exited for you!

Hurricane plan?

 

Does installation of a solar system affect the warranty on a new roof? I assume you have to drill holes, etc. to anchor the solar frame.

 

Ideally, the roofer and the solar installer will work this together. Or have the solar rack mounts installed as part of the roofing process. (A neighbor did this, but hasn't yet progressed to installing the solar, so has had naked rack attach points poking up for several years.)

I chose standing seam steel roofing, for which the racks are clamped to the seams with no penetrations. With extra mounting brackets for the roofing in that area, to address the increased wind loading caused by the solar panels. This choice was so that if we stay here for life, we won't have to deal with a roof needing replacement beneath a functioning solar system.

 

... a cloudless cold! day. Most otherwise great production days will be warm, with the panels running hot on the roof in the direct sun. Thanks to silicon's negative temperature coefficient, power output will be quite noticeably lower than their standard rating, which is for a cell temperature of 25C.

I think clipping will be somewhat common, more so on yours than on mine due to your larger gap between panel and inverter ratings. But just know that it happens, and is an intentional part of design for a finite budget. It is meant to get the greatest total return for a particular budget. A no-clipping design would be buying a bunch of rarely used inverter capacity, when that money might be better spent on the next smaller inverter and next larger solar panel when that combination can harvest more total annual energy over the local distribution of conditions.

That larger gap between component specs on your proposed system, vs what was normal when I built mine, jumped out at me. But on reflection, that makes sense because panel $/watt has dropped substantially since I was buying, but inverter prices less so. That shifts the tradeoff balance point or range. A truly rigorous cost analysis would change every time a possible component price changed (weekly? thrice weekly?), and would probably entail much more labor cost alone than that $400 inverter upgrade cost. Nobody does this for just a single household-sized system, instead use guidelines based on recent market conditions.

This does raise a lot of excitement. Hopefully permitting delays will not be long, as Jimbo and some others experienced.

Doing it DIY, I had the off-roof wiring done before the roofers completed that section of roof, then had the system (6-panel starter system) energized for testing late my second roof-work day, using an electric meter borrowed from the submeter base tracking the heat pump water heater. Then I simply didn't shut it down, but left it running and producing while waiting for official inspections. The regular electrical inspector arrived a couple days later, the utility's inspector / production-meter-installer several weeks later. Neither had any problem seeing the system (provisionally) on-line already. The utility's incentive paperwork even had a line for energy produced during this delay, so this was clearly expected.

 

that gave me a memory bite ... once commissioned - going out to the (old fashion back at that time, mechanical) kWh meter and just watching it run backward - all winter, into summer. my middle name ought'a be, "OCD"

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My new-fashioned digital meter has several bars along the bottom that run forward or backward, as appropriate, so this OCD condition continues.

Though for me, mostly just 3 seasons. On a typical winter day here, it isn't bright enough to run backwards except during infrequent sunbreaks.

 

Jerry, when you were talking to the individuals did the positioning of the house in relation to the sun ever come up? Our house is situated with the rear facing east and the front facing west. I always wondered if there is an optimum house geographic orientation to maximize solar collection?