Solar Panels for my home

Keep reading. I posted the DC and AC outputs later in the thread. I also posted the weather conditions and sun angles if you would like to calculate panel output for my 315 watt STC panels. I did the calc, now your turn.

Yes, and it is not your answer.

 

First, regarding the calculation. It is impossible for anyone to do an efficiency calculation without a proper electrical drawing or a detailed description of the installation along with spec sheets and at least a schematic drawing. Alternately, field tests measuring the actual system performance, preferably using strip recorders over time can provide actual data. DC power output from any source is susceptible to significant line loss unless it is generated at high voltages or large wire sizes are used. I am not aware of any solar panels commercially available for residential installation that are over 48 volts.

BTW, I run a 2000-watt inverter in my Prius via a paralleled set of 32 amp/hr gel cells. The recommended wire size for installations 3-feet and under is 1/0 AWG, and 3-feet is the maximum recommended distance from the source. DC love the copper!

Finally, the issue with DC and Edison v. Tesla. From the book of knowledge (aka Wikipedia):

"There were several technical factors that drove the adoption of alternating-current over direct-current. The direct-current system generated and distributed electrical power at the same voltage as used by the customer's lamps and motors. This required the use of large, costly distribution wires and forced generating plants to be near the loads. With the development of a practical transformer, alternating-current power could be sent long distances over relatively small wires at a conveniently high voltage, then reduced in voltage to that used by a customer. Alternating-current generating stations could be larger, more efficient, and the distribution wires were relatively less costly."
​

Among the ironic realities facing those of us in California is the existence of Southern California Edison. The name of our power distribution monopoly should be Southern California Tesla. Edison, for better or worse, would have nothing to do with deadly AC power. He almost certainly would also fight the emergence of new energy sources, such as the Mr. Fusion portable energy source developed by the eminent Doc Brown of Hill Valley.

 

Nonsense.
AC-power/DC-power

I'm glad you read wikipedia but you did not understand it. The problem for DC at the time was lack of a suitable and inexpensive transformer. Next time you are out and about on the www, check out the high voltage lines that connect regions. Guess the type of current. Here is a semi-quant graph for HVAC vs HVDC. Note that as distance increases the money argument for HVDC improves because the line savings overcome the terminal station costs.



Last, here is a calculator to figure lines losses
Electricity losses : voltage drop and energy losses free online calculator for AC and DC Power; electrical wire drop voltage quick calculation, cable energy losses, resistive heating, for three phase and single phase wiring
I used 8 AWG (3.26 mm) wire and the system runs DC from panels to inverter at ~ 2 - 8 Amps most of the time with voltage varying from 100 - 400 v

 

Ok .... to put the thread back onto a more benign nature - here are pictures of our 2 inverters, which have been running flawlessly for 10 years, this upcoming December.


Does one collectively (adding the total together) read this figure as almost 202K kWh's?
Or does one simplify it to a lower gWh number.
That's one question. The other question is even more convoluted

We've had a ONE plug in for over 8 years of solar operation, which still allowed us a bit of surplus. Now we have two plugins as of almost two years ago. The increased power consumption of 2 plugins has resulted in <1kWh/day, when averaged across almost 10 yrs of solar generation. Anticipating this, I recently bought & installed 4 additional panels that i installed on to the inverter pictured/registering the lower amount of output total - over the last 10 years.
The extra 4 panels is what brings our overall rating up from 7.1 to a 8.kW'sAC rating. If my back of the napkin numbers are correct this should slightly more than offset the additional 500kWh/month that the more power hungry plugin uses per month.
Yes? no? maybe? what do you think. Time will tell.
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Are the four new panels sited as advantageously as the others ?

 

our 2 gables ridge run due NW to SE.

So, the less used inverter faces North East (right side of the above picture). So these new 4 panels, were put on that side -

along with the existing 16 on that inverter pick up mostly the early morning sun, until noon. Then that side's ourput slowly drops.
.

 

Since I think you have two strings with central inverters the final result is going to very much depend on whether any additional shading is brought into play. That is probably more important than any orientation differences.

 

We don't really get any shade until after 4 in the winter evening, or 7, during June / highest Sun Apex. My estimation is 2.5 additional kWh's, per average 12hr summer/winter days .... ie at LEAST 22kWh's day ... being on the morning side of the home. That's about what the plugin uses/averages per day.
Oh ... the roof pitch between the two Gables comes into play as well. It's pretty gentle, about 2 & 12 ... 1 foot of rise every 6'.
For the past couple months that I had the new 4 panels working, I only notice a difference of about 1 to 2 kwh difference per day on each inverter. Looking forward to the new totals as we approach the summer solstice!
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Four panels ... producing 22 kWh a day ?

That seems really, really, really unlikely. I'll guess more in the 10 kWh a day ballpark in the summer and much less in the winter.

 

Reading through this thread, it seems $2/w Low to $4/w seems to be norm. If you do most of installation DIY, the cost can be reduced to $1-1.5/w range. It is still a big upfront cost for many home owner. My recent analysis gave me $45,000 upfront cost to install system that will cover whole house electricity needs with 17 years payback period. That is hardly a sound investment. I am continuing to shop around, but contemplating on smaller DIY system. Any recommendation on where to start on DIY solar installation?

 

50% of us will probably be dead in 17 years! If not from old age, it will be due to high voltage electrocution from repairing hybrid traction batteries or solar systems trying to save a few bucks, or from roof falls trying to squeeze one more panel onto the matrix facing the pool deck. And by that time solar power may be a dim memory of the past, like hi-fi audio, cassette players, 8-tracks and using heat to warm food.

 

know what? You're right ...
Gotta remember to carry those decimals. oops.
BTW, the new panels are actually 350kW's each. However, integrating them into strings made up of 225's causes them to de-rate to the existing wattages.
PV has gotten so cheap, that our 4 new 350's cost WAY less than our older 225's - paid for some 10yrs ago. One other dynamic to throw into the mix - since our system is now about a decade-old, these new panels may very well be de-rated even FURTHER than our older 225kW's because around the 10yr age there can be a measurable (albeit small) drop in yearly output. Will be keeping an eye on that. SunPower does have a 20-year ourput warranty, & so far we're still well within our warranted output.

17yrs is not so - because it's not just the light bill that you get to eliminate. when you factor in that you won't have to buy gas, & you don't have to earn the extra 30% pretax dollar that you would have had to earn to buy that gas.
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Yep ... one of the gotchas of of a central inverter setup: each panel in the string derates to the weakest link. I presume 350 watt was the size available ?

 

How much is your average monthly electric bill ?
What is your average monthly electricity consumption ?

Or are you talking about converting your current total energy use to electric ?

 

Our monthly electricity use is ~1,100kWh and at $0.181/kWh rate we pay ~$200/mo bill. I don't think converting everything to electric is feasible in our climate. It's too damn cold in winter to heat entire house by electric. We use 600 gal of oil in 5 month of heating and hot water, then another 200 gal for the rest of year for hot water only. But we have no A/C needs in summer.

 

Look at this financial calculator:



It tells you that spending your utility bill on a loan instead lets you buy ~ $40,000 worth of PV.
If the loan is from home equity and tax deductible -- even better.
And before you suspect me of plugging in an APR that is too low, remember that the monthly utility bill will increase with inflation while your monthly loan will not.

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That said, if I was in your shoes I would be looking for ways to use less energy.
My 3800 sqft home in Colorado with two plug-ins uses about 10 kWh a day.

 

yep - you just can't find high efficiency 225's any more - at least not with operating voltages of 40V.
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At my age, 20 year loan makes absolutely no sense. I don't want to go into retirement with a debt. I am sure there are way to conserve household energy use, but 10kWh a day is unrealistic for us. I have no idea how you do it. We use 10kWh a day just for the well pump alone.

 

I don't blame you for not wanting to go into debt. However, you ARE paying a monthly bill for utilities. If you pay a smaller monthly bill to a bank, with an end in sight, isn't that better?

Do you have organizations or companies that offer low cost, or free energy check-ups?
We live in MN, and are happily using electricity to cook, charge our cars, heat and cool our house. I don't know that it would be feasible for your house, but I would be surprised if some fairly major energy savings weren't available to you.

 

Sure, I have contacted several energy conservation groups in our area for information. I have already implemented most of low cost energy saving measures, such as insulation in attic, weather striping windows, changing to LED light bulbs, installing water saver showerhead, supplementing heat with wood burning stove, etc, etc.and of course driving fuel efficient Prius. Yet, solar electricity is still quite bit higher hardle to clear at moment. DIY installation of smaller system seems more manageable initial effort for now. I am not yet 100% convinced that PV is feasible solution for my situation, but I sure would love to free myself from dependency on fossil fuel. If I could go totally off grid that would be my dream come true.