I get $481 annually. I assume this -> non-economic?

True. If you want complete energy independence or the ability to generate energy while the grid is down, you need to factor in enough lithium batteries to cover your needs. With this setup, a relay disconnects you from the grid in a power outage and runs on solar and battery alone. When the grid comes back up the relay energizes and reconnects you to the grid.

I also have 23 micro inverters and while they should be very reliable, things do happen.

Just got my bill. $46.96 for a 2600 s/f home. Highest I have had all year was Aug at $151.12. Taxes included. 15 year old heat pump with gas backup on heat.

It is an interesting thought experiment. Since panels are estimated to produce significant output for 20 years we can make some comparisons.

If we invested $20k in the S&P 500 in 1999 it went through 9/11, 2 bull markets, 2 bear markets, and the greatest recession of our lifetime. Today that investment would be worth $62k.

If we invested $20k in solar PV in 1999 and our elect bills were $3000/yr, we would have saved $60k in bills or roughly even money. We just paid 20 years of elect. cost in advance. We know that rate increases were stiff in CA during that period, the savings probably would have been greater. Lighting and appliances are also far more efficient now so that would have some moderating effect on the rate increases by using less kwh per household.

you'd invest the monthly savings from the PV panels in an S&P Index fund, so figure that in too...

but wait!! there's more!

over the 20 yr period, there is a P() of new, improved output PV panels coming on the market, so...



Thx to Ron Popeil...

Good one Webb!

By dollar cost averaging $250/mo electricity savings into the S&P 500 over 20 years instead of investing $20k lump sum in 1999, you moderate the downturns and maximize the increases. As a result your investment would be worth $166k today. A 9% return rather than a 6% return. By spending $20k on solar and investing the monthly savings you net $100k over a $20k lump sum investment in 1999 in this simplified example.

https://dqydj.com/sp-500-periodic-reinvestment-calculator-dividends/

I average 42Kwh per day. I'm trying to figure out that line from RB. I found a site that gives a calculation for sizing and it appears I need a 15kw system to satisfy my electrical needs. From a quick search that a $17,000 system :eek::eek:

That seems terrible on first glance but if there's a 30% tax credit that drops the cost to 12,900 which would make payback a little less than 7 years. Might be worth a look. Only thing is, I'd probably use my heat pump more in the winter but if the calculator is right, based on a 15Kw system, standard module, fixed roof type, 14.08 system loss, 20 degree tilt and 180 azimuth I'd produce about 19465kWh per year which is about 3000kWh more than my current usage. I should have some wiggle room for increased consumption.

That actually sounds on the low side.

Prior to tax credit 2019

http://forums.pelicanparts.com/uploa...1576330442.png

This is a 15kw kit for $22,575. Installation not included.




https://www.gogreensolar.com/products/15080-watt-15kw-diy-solar-install-kit-w-solaredge-inverter

HOW MUCH SHOULD I PAY A CONTRACTOR TO INSTALL THE SOLAR KIT?
Any licensed general, electrical or solar contractor can install our solar kits. If you select to hire a contractor to install your solar kit, you should expect to pay approximately $1.00 per watt for labor, wire, conduit, fittings, breakers and other miscellaneous electrical components to complete the solar system installation. For a 10 kW (kilowatt) system, which is 10,000 watts, you can expect to pay $10,000 for installation. If needed, we can assist you with finding a contractor.

Here's the one I looked at
https://www.gogreensolar.com/products/copy-of-15-080-watt-15kw-diy-solar-panel-kit-w-string-inverter

Have to look into the string vs solar edge inverters. The array would fit on the south facing roof of my barn. I think I could handle the install since I've done the main service lines for several homes.

Delphos Ohio, using PV Watts, says you will get about 4.57 kWh per kW installed.

42kWh/day divided by 4.57 = 9.2kW to equal your usage. I would suggest rounding it to a 10 kW system.

Depending on your location and codes, you may need a licensed electrician to install. You will also generally need to work with your electric company and generally need to submit a modified one-line diagram for approval. They also usually want to inspect your system before you turn it on.

The issue with roof mounted solar is to insure you are tying into the rafters and not the decking. And that you are sealing the penetrations properly to prevent leaks. And finally, that you have the system setup to allow for thermal expansion/contraction.

If you have a lot of trees which might shade part of the system, you may want to use micro-inverters which adjust output of each panel individually. The other alternative is a central string inverter with "Optimizers", which is what Solar Edge does.

If your roof is clear of trees, then a straight 600V string inverter is fine and the least expensive way for grid-tied solar. Remember, this type of system will not operate when the power is out. And if you have a generator, the connection MUST be on the utility side of the transfer switch.

If you want a system that works when the utility is out, you will need a battery based system. These use "Charge Controllers" and feed the battery directly. Some do allow you to sell excess power to the utility.

As far as the Tax credit is concerned, you need to have it OPERATIONAL by Dec 31st, 2019 to get the 30% credit. Next year, the Federal Tax credit drops to 20%.

There is a bill in Congress to extend the Tax Credit. But Congress is "distracted" at the moment.

Around here a 10kW system will be about $25K

That is about what they are up my way.

As mentioned the NREL site says I can generate $481 of electricity annually with rooftop PV.

I found another site, which exposes the details a little more. Below is a screenshot of the result I got. This is with manually specifying as many panels as will physically fit on the roof. The site's default output had fewer panels.

http://forums.pelicanparts.com/uploa...1576340349.png

Does this mean that I simply can't use solar to generate all my home electricity, unless I can cut consumption by 50%? It looks like my house simply doesn't have the right roof area to interior volume ratio, plus I live in the rainy side of Oregon.

I don't know if James' 4.57 kWh per kW installed is a yearly average for your latitude. He's a sharp guy, so he probably took that into consideration. I also don't know if your average of 42 kWh per day is taking into consideration the fluctuation between seasons of high generation and low. Like I said, my 7.75 kW system generates a high of maybe 52 kWh per day during the high generation season and about half that during the low season.

Your rates are just staggering. Your system in my area (sw Okla) would save me a thousand a year. On your place it looks like 3 grand or more.

Anything is possible but because insolation in your area is 1/2 that of SoCal, you would need 2x the panels to generate the same output as Marv. You would probably need to mount them off the house in an ideal location to make the most of your sun exposure. This might be a $50k project so you have to decide if it makes sense.

Yes, like I said I probably have about three more years to break even. And as I said before, the impetus for going for it was my bill going from $495 (all electric house) the highest month to $595 the next year, which showed to me the amount they raised rates over that past year. Rates are so high, the County (City?) is considering establishing an alternate system to compete with SDG&E and offer up some choice for customers. Truthfully one of the major satisfactions is knowing I'm sticking it to the utility company even if it were possible to use the money in a better way investment wise. My conservative estimate at the time was over $3K+/yr. and it's higher now.