First post and question...

[solar pete]

Hi Shubunkin, and welcome to Solar Panel Talk, well yeah you can but is it cost effective, no, sounds like you dont really have a handle on this yet so I would suggest that much more reading of the relevant stickies in the grid tied and off grid sections.

Is there any way to connect batteries to store the surplus and not have it go to the grid? Yes this is a hybrid or off grid system, look, at the end of the day there is a whole bunch of rules and regulations that must be adhered too for safety reasons, electricity is dangerous and must not to be treated lightly rules are there for a very good reason you need to do more reading to get an understanding of the basics.

[J.P.M.]

Hi - Just joined and I have a question. Perhaps I just didn't know how to search the forums properly. We are building a house in NC and want to use solar, but the local co-op has severe disincentives for connecting to the grid (in addition to adding monthly fees, they will buy at wholesale and sell back to us at retail.) We would like to have a system where we could use our own solar but have back-up from the co-op. I thought about batteries but have heard they are not cost/ecologically efficient. Is there any way to have the house use solar as the priority, and only draw from the co-op when necessary (no feedback to co-op so no fees?) I know we can just minimize the solar to a small portion of our usage along with continual draw from the co-op, but that seems kind of contrary to the point of having solar in the first place.

Most folks don't do this, partly because it's not thought of or known too much, and partly because it's more up front $$, and partly because it's perceived as involving some probably unknown lifestyle adjustments, and partly other stuff, but one way to utilize and work with the sun and common sense is to design using heavier than standard insulation levels and better sealing techniques as well as solar tempering of the dwelling by passive solar techniques.

You'll never get off grid that way, at least not in NC, but you can sure put a big dent in an HVAC bill, and that's probably part of the goal. The techniques do work.

[Mike90250]

Figure the cost of a big battery bank , say $3,000
How much power can you buy for $3000 ?
Buy more batteries in 6 years when they wear out, another $3000 and be sure to add water every month, or you are going to buy batteries when you boil them dry.

Simple Grid Tie, is where the cost savings is. If you have Time Of Use rates, bias your solar array SW instead of due South.

[bcroe]

Someone toured my solar today and asked about batteries. I asked them to imagine what my
lawn would look like with 27,000 car batteries strung together, to deal with my net metering
setup capacity?

Some net metering plans (mine) don't buy and sell, they just charge me for insufficient
generation, and keep for free any excess energy left on reset date 1 April. A great deal,
the energy I usually have surplus for them didn't cost me anything extra.

If you can't get such a deal, next best is try to run all your heavy loads at the same time
the sun is shining, sell power to yourself 1:1 as much as possible. Bruce Roe

[Sunking]

Is there any way to have the house use solar as the priority, and only draw from the co-op when necessary (no feedback to co-op so no fees?) I know we can just minimize the solar to a small portion of our usage along with continual draw from the co-op, but that seems kind of contrary to the point of having solar in the first place.

Sounds like you have no money management skills. If you are connected to the grid in anyway, is a grid interactive system, and your rates will be based on the utility policy. But to do what you want is just plain silly. I fully understand your utility sells at retail and buys at wholesale as that is the way it should be. But the idea of limiting a grid interactive system to never export excess power is just plain ignorant. If you export excess power, it is worth real money to you in the form of a credit on your bill, limiting power and not selling excess power is a pure loss on your part and can never be recovered.

[foo1bar]

Yes that's kind of what I need to do .. but I'm having a hard time finding anyone that has gone on a net metering program with a diy system ..

I installed my system and am on net metering.

It's really no different than a non-DIY system with net metering. (same materials, same inspections, just the labor is my own instead of having paid someone)

I used Solaredge for my system due to shading and different orientations.

[Shubunkin]

Shubunkin here again... First, thanks so much to the folks who tried to understand my concerns. To the people who commented on my intelligence, inappropriate fear of electricity, or financial management skills, thanks for reminding me of the hazards associated with posting online. You can stop reading here and save yourself an ulcer.

To anyone still willing to listen, perhaps this will explain it better. Our co-op does NOT do net metering. (Net metering is a no-brainer that we would jump on. Too bad we can't have it.) The new house is being built and will, I hope, be tight and energy efficient. I do not know how much electricity it will use. In the current rental, we are using an average of about 45 kwh/day. The new house will have room for about 15 panels - am I correct that will offset about 15 kwh/day best case? So the solar will make a dent, perhaps close to a third if we are very lucky. We anticipate waiting until we move into the new house and monitoring energy usage before we make a final decision on whether/what to install.

I understand that money makes the world go around; however, I hope there are at least a few people on this site who also worry about the planet. We are retired, and who knows if we will even live long enough to get any direct ROI from solar. However, because we can afford it, I like to think we could reduce our pollution a tiny bit while we are still here.

Cost of the panels aside, the co-op requires that we pay an additional fee of $6.50 per month for the privilege of tying into their system. They will then buy any excess solar from us at 5 cents per kwh and sell it back to us (probably that same evening) for 10.5 cents - more than twice as much. So any excess capacity will cost us 5.5 cents per kwh (the difference between what they will pay for it and what we pay to replace it later) plus the additional 6.50 per month in rag charges. If we were able to do some parallel system, we would at least save ourselves the 6.50 per month, and if we had some kind of battery, potentially we could save some of that excess energy for our own use a little later in the day. At any rate, I would love to be educated on how to arrange for the house to use power from the inverter first, with the ability to switch to the co-op feed when necessary. Perhaps it is not possible, but it seemed that any solution would likely be found here.

[Mike90250]

That is not an unusual billing they do. After you are in and settled, see what your usage is. $7 month for RAG might save you $50 in billing,
Batteries will never pay back, always a hole for money to go into.

[SunEagle]

Shubunkin here again... First, thanks so much to the folks who tried to understand my concerns. To the people who commented on my intelligence, inappropriate fear of electricity, or financial management skills, thanks for reminding me of the hazards associated with posting online. You can stop reading here and save yourself an ulcer.

To anyone still willing to listen, perhaps this will explain it better. Our co-op does NOT do net metering. (Net metering is a no-brainer that we would jump on. Too bad we can't have it.) The new house is being built and will, I hope, be tight and energy efficient. I do not know how much electricity it will use. In the current rental, we are using an average of about 45 kwh/day. The new house will have room for about 15 panels - am I correct that will offset about 15 kwh/day best case? So the solar will make a dent, perhaps close to a third if we are very lucky. We anticipate waiting until we move into the new house and monitoring energy usage before we make a final decision on whether/what to install.

I understand that money makes the world go around; however, I hope there are at least a few people on this site who also worry about the planet. We are retired, and who knows if we will even live long enough to get any direct ROI from solar. However, because we can afford it, I like to think we could reduce our pollution a tiny bit while we are still here.

Cost of the panels aside, the co-op requires that we pay an additional fee of $6.50 per month for the privilege of tying into their system. They will then buy any excess solar from us at 5 cents per kwh and sell it back to us (probably that same evening) for 10.5 cents - more than twice as much. So any excess capacity will cost us 5.5 cents per kwh (the difference between what they will pay for it and what we pay to replace it later) plus the additional 6.50 per month in rag charges. If we were able to do some parallel system, we would at least save ourselves the 6.50 per month, and if we had some kind of battery, potentially we could save some of that excess energy for our own use a little later in the day. At any rate, I would love to be educated on how to arrange for the house to use power from the inverter first, with the ability to switch to the co-op feed when necessary. Perhaps it is not possible, but it seemed that any solution would likely be found here.

Actually your co-op is using some version of "net metering". They will just not pay you the same for each excess kWh you send them that you purchase from them. That is very typical of a lot of POCO's that do not allow "full" Net metering.

Why are you looking at the cost difference between what you pay and what they pay you? That 5.5 cents / kWh is not a loss as much as it just increases the time for your ROI which from what you have said you really don't care about.

Going with batteries is again totally opposite of being green which is again contradictory of what you want to do.

I understand the desire to use solar but IMO you really don't understand the technology and how it works so you tend to feel it is very green as well as save you a lot of money. Neither of those are really true. The only way to really save money over a period of time would be to install a complete grid tie system with or without net metering.

At least you get something from your co-op for the excess you generate. It will always cost you more than 5.5 cents per kWh from a battery system so that is where you will lose more money and be less green.

If you want to be green and save money then just stop using an ICE vehicle and turn off your electric appliances when they can't be powered from a renewable source.

[foo1bar]

fee of $6.50 per month for the privilege of tying into their system. They will then buy any excess solar from us at 5 cents per kwh and sell it back to us (probably that same evening) for 10.5 cents - more than twice as much. So any excess capacity will cost us 5.5 cents per kwh.

I would phrase it as generation that exceeds the minute by minute demand only saves you 5 cents per kwh.
It is not really costing you... You just aren't saving as much.

And they aren't selling you back the kwh you generated earlier in the day. They sold that to your neighbors when it went in the grid. They are selling you an equivalent kwh. A kwh that they generated ( or bought from a generator at that moment).

How many kwh are generated from 15 panels really depends on the location, panel efficiency, and angles (tilt and azimuth).

[jflorey2]

Shubunkin here again... First, thanks so much to the folks who tried to understand my concerns. To the people who commented on my intelligence, inappropriate fear of electricity, or financial management skills, thanks for reminding me of the hazards associated with posting online. You can stop reading here and save yourself an ulcer.

Eh, ignore him. He's not happy unless you're not happy.

To anyone still willing to listen, perhaps this will explain it better. Our co-op does NOT do net metering. (Net metering is a no-brainer that we would jump on. Too bad we can't have it.) The new house is being built and will, I hope, be tight and energy efficient. I do not know how much electricity it will use. In the current rental, we are using an average of about 45 kwh/day. The new house will have room for about 15 panels - am I correct that will offset about 15 kwh/day best case?

Depends on:

-Where you live (average sun hours; NREL has good tables that will give you an estimate)
-What your array orientation is (south or southwest is ideal again depending on location)
-What the elevation angle your array is (an angle close to your latitude, or a little flatter, is generally ideal)
-What the available area is
-What the efficiency of the array is (can vary from about 14 to 18%)

In my area I can count on about 5.6 kwhr/m^2/day average throughout the year. So 1 meter of area gets me 5.6kwhr. So multiply that by the area of a typical panel (1.6 sq m) and efficiency (18%) and it will give you about 1.8kwhr/day in "ideal" (STC) conditions. Add in dirt on the panel, less than ideal orientation, hot panels etc and you'd see about 1.3kwhr/day per panel.

Cost of the panels aside, the co-op requires that we pay an additional fee of $6.50 per month for the privilege of tying into their system. They will then buy any excess solar from us at 5 cents per kwh and sell it back to us (probably that same evening) for 10.5 cents - more than twice as much.

OK, that's a lot better than I thought. It sounds like a single meter system. That means if you move your consumption to the daytime (i.e. run A/C, washing machine loads, dishwasher etc) then you will offset that use by 100%. You offset the remainder of your use by 50%.

It also sounds like you pay a flat rate for power rather than time-of-use, which isn't great for solar since solar generates during times of peak power pricing.

It will be hard to get very accurate numbers until you are moved in and have the new consumption figures.

So any excess capacity will cost us 5.5 cents per kwh (the difference between what they will pay for it and what we pay to replace it later) plus the additional 6.50 per month in rag charges. If we were able to do some parallel system, we would at least save ourselves the 6.50 per month, and if we had some kind of battery, potentially we could save some of that excess energy for our own use a little later in the day.

It's unlikely that they will say "oh, in that case, no connection charge!" if you add a battery to your system. And as I mentioned before, batteries just aren't cost effective. If you have the extra money, more solar would probably be a better investment than a battery.

At any rate, I would love to be educated on how to arrange for the house to use power from the inverter first, with the ability to switch to the co-op feed when necessary.

Any single meter grid tie system does that automatically. From a billing perspective, the house _always_ uses solar power first.

Battery based systems are a lot more complicated but they have similar modes; you can configure them to prioritize self consumption (although that's hard on the batteries of course.)

[Shubunkin]

OK, thanks all for the input. I really was hoping for a way to get around the connection charge, and it seems as if that just isn't possible. Maybe it will be lost in the noise; we will know better when we have actual usage data. At least now I know we really, really, really don't want batteries!