Let the sun shine

Tom McIntyre

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We are celebrating our solar PV system that just set a personal best for the Month of March with a few hours still to go.

solarproduction.png
 
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shutterbug

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:thumb:
What's the break even point? A few years yet I assume.
 

glenhead

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We're looking at a payback of just under eight years on ours. We have a 15kW system that's been in for four years next month. We've generated 58.41MWh in that time. Annual electricity bills run a smidgen over $200, about what it was for a month pre-solar. All heating-type things we have are propane-powered, so we really never used a lot of electricity in the first place.

Our electricity provider rolls excess generation month-to-month, so (to a point) sunny spring and fall months provide coverage for cloudy hot months. One annoying thing we didn't know up front is that they "dump the bucket" at the end of each contract year. Since our contract started in May, they dump the danged bucket right at the start of central-Texas summer. If the bucket dumped in January or something our bill would be near zero. Guess what we're going to do when our five-year contract runs out next year?

We live in an unincorporated area. The power companies serving our area didn't offer net metering (where one kW of power fed to the grid pays for one kW drawn from the grid) until the month before we ordered our system. We'd talked to the solar people several times before that; the payback without net metering was around 22 years.

We have solar power and I drive a Chevy Volt most of the time. That means my 34-mile round trip to work is made 1) without burning a drop of gasoline and 2) without paying a penny to charge the Volt most days when I get home. (Except for when I drive my Suburban, that is.) I'm by far the most conservative member of my group at work. I just sit and keep my mouth shut so I don't stir up the others. Everyone else in my group lives many miles from work, drives a gas guzzler of some sort (except for the one gal who drives a Prius), and lives in a huge house, most with pools. They gave me grief when I got my first Volt, and then accused me of "going green" when we got the solar system. My response? "Y'all do a good job of talking the talk, expecting everyone else to change their ways to fit your demands while you do nothing. What I do saves me money - all the 'green' stuff is a side benefit that I don't care about. Plus, what are the first two syllables of 'conservative'? Try walking the walk before you give someone else grief."

Yeah, I'm not particularly popular at work. :)

Glen
 

Tom McIntyre

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In Massachusetts with National Grid, we have permanent net metering and our credit just accumulates. In addition we get the benefit of a 10 year solar Renewable Energy Credit that auctions off each Megawatt hour to those bad CO2 producers at, roughly, $250 each. Had we built two years sooner the credit would be about 50% more. That has changed for current builds to cash rebate per KWH with a permanent contract but less than half the rate of our deal.

There were substantial tax credits when we built from both the Feds and MA. The vendor arranged for 2.99% loan, so that the structure was nearly neutral in cost from the beginning. I paid off the loan two years early when the interest rates dropped dramatically.

Our net metering has a an over $300 credit coming out of last winter and has not been below zero since the second year of production. We do not make any interest on that money but the cushion is nice.

The panels and inverter have a nominal lifetime of 10 years but seem to do better than that. If there is a loss in output from the system it seems to be overcome by all the extra sunshine from global warming.
 

FDelGreco

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What happens when the MA winter snows come? Are you up on the roof shoveling? <grin>

Frank
 

Tom McIntyre

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That is actually the worst situation. There is no economical way to remove the snow cover. There are panel heaters that exist, but no one thinks they are worth the cost.

I think that one of the reasons our power output has been going up for the last year+ is that they snow may be becoming a thing of the past.

The solar panels make a nice climate sensor that lets you do averages over time and/or solar angle and so forth.
 

Tom McIntyre

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If anyone wants they are free to explore our installation 18332 - Overview'
 

FDelGreco

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Yes, but can I charge a Tesla on it and run my 5 ton air conditioner at the same time?<grin>

Frank
 

Tom McIntyre

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Tesla car or Tesla Power Wall? I think the prices need to come down a bit for the Power Wall to work for me. The benefit is that you can charge your battery and save money over putting the extra energy into the grid when you already have a credit balance.

If you empty the Power Wall every night you maximize your savings but you do not have it for emergency power. We have had about 5 days total outage in the last 3 years.

Up here all of the tax benefits and net metering are limited to residential under 10Kw. If you want more than that you need to go commercial and the financial structure changes.
 

glenhead

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Yes, but can I charge a Tesla on it and run my 5 ton air conditioner at the same time?<grin>

Frank
I can charge my Volt on my Level 2 charger while our 5-ton AC runs and watch the meter run backwards. I just went outside and checked it to make sure it would still do that, and yeah, it does. Except when a cloud gets in the way - a wispy cirrus patch clipped the sun and dropped the output by about 30% while I was standing there and the meter started slo-o-o-owly running forwards, then it cleared and the meter ran backwards again. So far today (at 1432CDT) we've generated 33.8kWh under mostly-clear skies.

We ran a bunch of errands over lunch and the Volt's battery had 5 EV miles left on it, so it's charging. It's 85F in the back yard. The electricity meter is three feet from the AC compressor and I went out while it was running. So yes, I'm sure they were both running, along with the TV, six computers, and various lights.

The Volt pulls 7.5kW on Level 2 compared to 11.5kW for the Tesla, so I can't swear it would run backwards if a Tesla was charging. I doubt seriously that it would - but it'd be danged close. Add another half-dozen panels to my array and it would for sure.

Glen
 

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