Our Solar Electric Panels: Done!

My preferred way to figure out costs and attractiveness in a money sense is to use an amortization calculator, set to a monthly payment equal to my average monthly utility bill savings.

 

Re: Our Solar Electric Panels

In a private msg, Cactuscong suggested that I assume 8K kWh annual usage. That makes good sense based upon my extrapolation and the expectation that May and June are usually pretty hot months.

I really appreciate your providing this advice, as I don't need an unhappy surprise at year-end. Looks like financial payback will be around 10 years given the reduced rebate and the need to scale up the system to ~20 panels. The inverter quoted is the larger of the two in the datasheet, so it should be able to handle the additional power output.

I'm planning to obtain another quote or two, then will obtain HOA review of the plans. Also need to wait for a CD to mature so that I'll have the $$$ to fund this. Will take action on this in a couple of months. Thanks to all for helping me to assess the needed solar power capacity and financial implications; you guys are great!

 

A telemarketer from Sunpower called me today and provided a rough price estimate of $32K prior to incentives, for a 3.4 kW system. Since I already have a bid that is priced at ~2/3 of that, I was not concerned. The telemarketer is going to have TFS call me to provide a real bid.

 

What the heck am I doing wrong? LOL. I use more electricity than you do, have a slightly smaller home, and live in a state with seasons other than "hot" and "smoldering" lol. Of course, a lot of the usage also depends on what is using electric vs nat gas as well. For me, everything is electric, and I know the water heater (only 4 yrs old) adds quite a bit of usage to my bill. Plus the deep freezer (abt 3 yrs old) probably doesn't help.

FWIW, I've got 12" of attic insulation and the standard 2x4 wall studs. I'm probably out of options at this point in regards to efficiency with the "energy hogs". I keep the A/C between 75 - 78 and keep the fan on constantly (evens out the upstairs/downstairs temps, plus brings that cooler air upstairs).

 

What direction and angle will the panels be mounted? Using that information, as well as your location, one can plug the data into PVwatts and confirm the estimate. Are there any shade issues?

$6.50/watt is a good price - especially for SunPower panels which tend to be more expensive as they are a decent amount more efficient than average (The average module tends to be around 14-15% efficient). They are great panels if you are space limited at all - otherwise you can often get other panels a bit cheaper if you have the room.

 

Yes, my water heater and two heating furnaces are powered by natural gas. The casita has an electric heat pump that provides both A/C and heat.

My prior home in south Orange County, CA (3,000 sq. ft., built in 1994) was a real energy hog, the monthly electric bill in summer months was easily $300+ with the A/C set at what I considered uncomfortably hot levels. The swimming pool pump alone accounted for ~$100 of that amount, it was crazy. A wasteful way to live, glad to be out of there now.

Thanks, I am inclined to favor SunPower panels to reduce the number of panels mounted on the roof.

The panels will be facing south. The angle will depend upon the installer's recommendation and HOA approval. No shade issues as the surrounding homes are all one-story and the nearby trees are on my property and are not that tall anyway. I like the idea of fewer panels operating more efficiently. It now looks like I will need 20 panels to comfortably meet 100% of annual electric usage, as I am going to assume consumption of 8K kWh for planning purposes.

 

If you are using solar electric to heat hot water you are engaging in a very inefficient practice. It is way more efficient to convert solar to heat directly into hot water than it is to convert it to electricity. (much cheaper per BTU as well). Solar hot water is much more cost effective than PV. I suggest to all my clients that do Solar hot water first, or at a minimum convert to gas fired (natural or propane) hot water to avoid using electricity. (Personally, I wouldn't (and don"t) use electricity for any heat generating appliance except a soldering iron. In our off grid house we even have a propane toaster!)
If you live in a climate where you use A/C on a regular basis, a effective option is to convert to a heat recapturing heat pump. This allows the hot side of the A/C to pick up the other wise waste heat, and turn it into hot water. The has two benefits, the first is that it allows the A/C to run more efficiently (and use less energy) and it gives you "free hot water". Truly a win/win. If you don't use A/C, consider solar hot water. After conservation, it is the first modification to do,, long before Pv solar.

 

The best reason for the Sunpower panels - which are more
efficient but cost more - is if you are space constrained.
A 230w Sunpower measures 61" x 31", versus a more
traditional Sharp 230w panel at 64" x 39"...that's a 20%
savings in footprint size.

Note that you can't use the Enphase micro-inverters with
Sunpower, as that combination is not certified as being
compatible. The Enphase inverters can be in the range
of 5-10% more efficient...or the equivalent of one or two
solar panels in your case.

 

I thinking about this, is this a good deal?
Through Solar Conduit’s partnership with a leading national renewable energy firm, we can provide design and installation of a 6,000 watt Solar Electric System in most Texas locations for the special price of only $5.99/watt!
The cost of this system, after the Federal Tax Credit, is only, $25,158!
http://solarconduit.com/shop/index....grid-tie-solar-system-installed-in-texas.html

 

You'll need to figure out the annual kWh produced by this proposed system and calculate what you'll save on your monthly electric bill. Then you can determine what is the payback on the $25K investment and whether that makes sense to you or not.

 

An update: I've signed a contract today for a 5.4 kW system which is estimated to produce 9,400 kWh annually. This system uses 24 Schott Poly 225W modules.

The gross price is $28K and the Tucson Electric Power rebate will be $16K so I need to pay $11.8K. After the Federal and AZ income tax credits, the net system cost will be $7.2K. My guess is that payback will be attained in 9 years, shorter if electric rates rise.

I also considered a similar SunPower system with 24 215W modules, but the net system cost was $9.3K. I did not perceive sufficient value in that system to pay the incremental $2.1K.

CactusCoug estimated I would need a system producing 8,100 kWh. My wife estimated our annual consumption will be 9,060 kWh. Our installer originally recommended a 22 module system producing 8,600 kWh.

We decided to add two modules to the installer's recommendation because the incremental cost ($443) was quite low, and this added capacity will help as the array ages and considering the effect of hot weather as hill advised above.

My wife tolerates me setting the AC thermostat at a lower temp than she would prefer. She says she would set the thermostat around 7-8 degrees warmer if it was up to her.

So I said that if I kick the bucket, what is she going to do with all this electric generating capacity since Tucson Electric Power is only going to pay $0.03 per kWh for excess electricity produced? She replied that she'd probably buy an electric car... We already have a 240VAC outlet in the garage.

The next steps include applying to Tucson Electric Power to reserve the rebate funds, and obtaining HOA approval for the project. The system probably won't be installed until August or thereabouts.

Special thanks to CactusCoug who shared many details of his system in north Tucson, and who also recommended the installer that I eventually selected, Technicians for Sustainability in Tucson, AZ.

 

Congratulations.
I have only 8 solar electric panels (180 w/pan.) since 2008 May : it's a beginning but it's better than no one. There is room for more on the roof but In Belgium we can't add panels on an inverter even if it's great enough.
I will replace the pump of the central heating by a 'class 1' => 500 kw/h less on a year
Grundfos USA

 

That's a bummer that they only pay $0.03 per kWh for excess electricity. I'd imagine you get charged a lot more than that, even at the lowest tier.

What if she really wants that electric car? :blink:

It it is too bad that the payback period is fairly long and that it requires such a high (presumably) upfront cost.

 

I'd live with the extra heat and get the electric car!

 

Yes, the summer kWh rate is ~$0.10. Since TEP is contributing $16K towards this project, I can't complain that they are paying for kWh at the wholesale electricity rate while charging at the retail rate. That is why the general advice is to buy a system that produces ~90% of your requirements since you're not getting much credit for excess electricity produced. (In other areas, the kWh rate paid by the electric utility may be the same as the rate charged.)

When electric car technology has matured (and prices decreased) in another 10 years or so, we might be in the market at that time.

If there were no utility or tax incentives, the solar power system payback would be ~33 years, which exceeds my personal planning horizon and consequently I would not make the investment now.

 

Glad to hear you have decided to make the jump and join us on the PV! Does AZ also allow REC sales? If so, that'll cut down your payback period significantly! I've been bringing in around $200-250 for each REC that's sold. If you produce 9000 kw/h each year, that could add up to quite a bit!! I get closer to 6000 production wise, but I'm not out in AZ nor am I exactly ideally situated. Usage for me really depends on oil prices in the winter - i have an electric heat pump & oil furnace (on top of the wood pellet stove). I ran the oil furnace last year, as oil prices had come down a bit and it's a MUCH warmer heat.

Anyway, congrats!

 

Thanks. Pls say more regarding to whom you are selling the RECs.

In consideration for Tucson Electric Power providing its rebate, I have to agree to assign the RECs to TEP for a 20 year period (see page 1-5 of following link)
http://www.tucsonelectric.com/Docs/RESTDocs/2010TEP_RECPPFinal.pdf

 

Congratulations! I bet this will be exciting to you!

Please do publish your PV power yields a few months
after installation. My own rough estimate of your
annual yield is:

5.4 kW * 80% DC-to-AC efficiency * 5.5 solar hours/day (Tucson)
* 365 days/year = 8672 kWh per year

This suggests that your utility's rebate is $3/watt, correct?
My utility in MO gives $2/DC-watt.

What kind/brand of inverter are you getting? I
decided to do Enphase micro-inverters because I
am installing on two differently facing roof surfaces.

--

My 3kW PV array is supposed to install at the end of
this month. Inspired by your own example of highly
insulating your home, I got further prepared by
adding 25% more R30 insulation to my attic a couple
of weeks ago.

With regard to payback period, that is an important
criteria, but economics weren't the primary factor in
my decision to go forward. I wanted to reduce my
fossil fuel footprint, lead by example in employing
renewable energy, and reduce the burden all of us
bear for the pollution and loss of life inherent to
coal and oil exploration and production. Permanently
saving money on my monthly bill and avoiding a
portion of future electricity rate hikes were gravy.