New to Grid Tied Home Solar...

[Redneck in training]

I just put 3.84 kW of solar panels on a house we bought in town. 12 320 W panels to fill whole south facing roof. But I bought 7.7 kW inverter because I see electric car in our future. So we could add another 6 kW on the east facing roof. The total investment in hardware before tax credit was 6940 USD. Our utility allows DIY so I hired a helper (younger guy) for two days to help me with the installation on the roof. The sweet spot of current cost of the solar panels is 320W for 205 USD or 64 cents/W or about $1.65/W (before tax credit) including the, rapid shutdown modules, wiring, racking, breakers, disconnect switch and 5 kW inverter. Tax credit for 2020 is 26%. It drops to 22% in 2021. Estimated break even point (assuming constant cost of electric power) about 7 years.


Day 1


Day 2

 

[MossRoad]

Good luck with it. I find this stuff interesting. :thumbsup:

 

[Redneck in training]

Our current house has 24 kW of solar because we heat with electricity. We produce about double of our consumption but we still have electric bill about 139 USD/month. Our rural utility doesn't offer net metering. With net metering we would make about 200-300/month. Nevertheless we are approaching the break even point. Th e problem with solar is cost of installation. But I found that it is very DIY. In fact it is almost impossible to do it wrong.

 

[Alien]

We only have a 3.9 kW inverter (21 panels) about 8 years old now so I guess, old technology. Last couple of power bills we were in credit about $50 and that is using Reverse cycle air for heating. (I'm a sook) We are lucky as we get 50c per kW for excess so it helps a lot. Locked in for another 7 years.
By then I will have installed a larger system so that we should never have to pay for grid power again.

I should mention, our bills are 3 monthly. Most we have had to pay was $200 and that was a year or two ago.
I used to monitor it, it has paid for itself 3 times over now and original cost back then with extra bracket framing was $11,000
Now you get a lot more for less than half the price.
No maintenance whatsoever so far.

 

[ultrarunner]

Expecting a check again for excess... helps offset the high cost of water and sewer runs about $125 per month BEFORE a drop of water used... so I'm pleased to not have an electric bill.... water pencils out at about a penny a gallon.

Many of the 19 year old system are being replaced...

One of the Docs offered his 2009 3kW system for $1,000.

He is increasing 3 fold due to electric vehicle...

 

[Redneck in training]

We only have a 3.9 kW inverter (21 panels) about 8 years old now so I guess, old technology. Last couple of power bills we were in credit about $50 and that is using Reverse cycle air for heating. (I'm a sook) We are lucky as we get 50c per kW for excess so it helps a lot. Locked in for another 7 years.
By then I will have installed a larger system so that we should never have to pay for grid power again.

I should mention, our bills are 3 monthly. Most we have had to pay was $200 and that was a year or two ago.
I used to monitor it, it has paid for itself 3 times over now and original cost back then with extra bracket framing was $11,000
Now you get a lot more for less than half the price.
No maintenance whatsoever so far.

We installed our first system at the end of 2012 right after the cost of the panels collapsed below a $1/W. We have 96 250W panels with microinverters.

 

[Jim Nelson]

I learned something Thursday,12-3-20, when our power co turned the power off from 2:00 am til 8:00 pm. I checked my production the next day after power was restored and it said 0 production for 12-3-20. Later that day I went to get my mail and there was a service truck at the neighbors so I stopped and asked him why. He said that the solar system needs power either from a battery system, like the Tesla wall, or a generator system when the power is out. He was a real nice guy who lives in a rural area like ours and has solar, He said he told his wife that he was going to start the generator and she complained about the noise disturbing neighbors. He took her outside and all you could hear was generators.
I called the next day to have an electrician come out and wire my gen. set to the house so this doesn't happen again, he said it would be a while as he was getting calls every few minutes for the same thing.

Just a warning in case any of you, like me, were not aware of this.

 

[orezok]

I learned something Thursday,12-3-20, when our power co turned the power off from 2:00 am til 8:00 pm. I checked my production the next day after power was restored and it said 0 production for 12-3-20. Later that day I went to get my mail and there was a service truck at the neighbors so I stopped and asked him why. He said that the solar system needs power either from a battery system, like the Tesla wall, or a generator system when the power is out. He was a real nice guy who lives in a rural area like ours and has solar, He said he told his wife that he was going to start the generator and she complained about the noise disturbing neighbors. He took her outside and all you could hear was generators.
I called the next day to have an electrician come out and wire my gen. set to the house so this doesn't happen again, he said it would be a while as he was getting calls every few minutes for the same thing.

Just a warning in case any of you, like me, were not aware of this.

The reason your solar shuts down when the grid power goes out is to keep from electrocuting a lineman from a back feed.

 

[ultrarunner]

I think it would still be down with generator because it is grid tied?

 

[Jim Nelson]

Well the service guy from S.D.G.&E. said that if you have a generator running it will work, this of course requires that the generator is properly wired into the house so that it cannot feed back into the system. He told me that he has this system and it works great and the solar will supply power over what the gen. set puts out. As I understood him the solar needs the a.c. to act like an exciter for the system.

I am clueless and that is why I asked him in the first place. I can't imagine why he would tell me to do something that may kill him but as I said I'm clueless.

 

[ultrarunner]

Will the solar self limit when it can't send surplus to the grid?

Maybe the generator will slo to eco mode if solar providing.

I had asked the same question and never did find out except was told I needed a battery bank to make it all play nice.

 

[cqaigy2]

So the grid tied solar would still produce if it sees what it thinks it "line" voltage. I guess that's pretty obvious to some, but seems pretty clever to me.

 

[ultrarunner]

Yes but where does the excess go if not able to go to grid... sending to generator thinking it's grid can't be a good thing.

 

[ning]

A grid tie system needs to be able to disconnect from the grid and form its own "microgrid" if the grid goes down if you want to be able to keep using your own power. Utilities these days don't allow interconnection without automated disconnecting if the grid goes down, because they don't want to have power on a line they think is down.

A microgrid needs a sufficient source of power to handle transient loads; typically this is done with battery storage & PV, though it can be done with a (constantly running) generator. I assume you could do it with a generator + PV and no batteries, but that generator needs to be running in case there's not enough juice coming from the PV for peak loads (like your A/C starting up, which can easily pull 100A for a short period).

A lot of people were caught unawares during last year's PSPS in California when they had no power despite having lots of PV.

 

[Jim Nelson]

I don't know the answers to these questions but will be sure to ask when the electrician comes to hook up the gen. set. One thing the utility guy did say was that with my sized gen. I wouldn't be able to handle A.C.,electric oven, or dryer. It certainly seems to me that the power needs someplace to go like a battery system when usage is low and production is high, which is most of the time for us. Even in that situation where does the power go if batteries are charged and usage doesn't keep up with out put from p.v.. In the conversation he mentioned either a gen. or battery system and I told him I couldn't afford a battery system and didn't think they were a good investment yet and he agreed saying he just used a portable gen..
It's interesting but there is still a lot to learn.

 

[cqaigy2]

Microgrids, I wonder what the pros and cons are for the large energy producers. I'm guessing that will have the largest effect of whether that technology gets adopted.

 

[ultrarunner]

There are Solar Inverters that provide a single outlet independent of grid... Secure Power Supply

So when the grid goes down you you still have 2000 Watts provided enough sun generation...

Use your Grid-Tie Solar System During a Blackout | Webo Solar

 

[Jim Nelson]

I'm beginning to believe there was some misunderstanding between myself and the utility guy I was talking to. I thought it was too good to be true at the time and believe even more so after reading more on the subject. It sure would be nice though.
I am going to go ahead with having my generator set up just in case. I do believe this will become more common here even though this is just the 2nd time we have had our power shut off and by far the longest at 18 hours.

 

[grsthegreat]

Im an electrician, but have next to no knowledge on off grid and grid tied systems. All i know is my sister fell for scam install years ago, she basically saves nothing after utility adds on utility line use charges. I maintain some generators for off grid homes, and thats the jist of my experiences. When off grid, grid tied, power walls, etc started to come online, i was just winding down my career, and didnt want to add to my knowledge base.

I would think needing to run a generator to allow power use from solar seems kinda nuts. What am i missing. If your needing to run a generator, why use solar

 

[MossRoad]

Im an electrician, but have next to no knowledge on off grid and grid tied systems. All i know is my sister fell for scam install years ago, she basically saves nothing after utility adds on utility line use charges. I maintain some generators for off grid homes, and thats the jist of my experiences. When off grid, grid tied, power walls, etc started to come online, i was just winding down my career, and didnt want to add to my knowledge base.

I would think needing to run a generator to allow power use from solar seems kinda nuts. What am i missing. If your needing to run a generator, why use solar

Seems that most home solar systems exist solely to cut power bills VS generating your own power in an outage.

My take on it is that the solar back-spins your meter backwards when it's producing more power than you're immediately using. When you need more than it can produce, it takes power from the grid and your meter spins forward.

If there's a power outage, it shuts down your solar system to prevent back-feeding power to the grid.

If you had batteries, your solar system could stay on and charge the batteries and you could have power during an outage.

You can't pull power directly from a solar system to, say, your refrigerator. It needs to go through an inverter. Morning, evening, clouds, rain, etc... would make it highly unlikely that you could regularly draw power directly form the solar system, that's why you need batteries or the grid to act as a source.

As to having a generator, it wouldn't make sense to run a generator so that your solar system could come on and not put out anything, since your running the generator.... that whole part doesn't make sense to me at all.

As I see it, if I did get a solar system, it would not only be capable of reducing my electric bill, but it would also be capable of powering my home in a power outage, which means the additional costs of batteries and probably a generator.

I guess I'm thinking more off-grid than most typical installations.