Review of suggested system

Is this a place where I can post a quote by a local company to install a solar system for me and get opinions? I am located in an area where there are very few companies doing installations and hate to go with only one quote.
Can I post the proposal and price here or is that not allowed?

Sure, but you might want to blur your personal info.

Post away, just hide the name & address.

No other bids to compare with kinda gets you stuck with the options of "Take it" or "Leave it."

the company is proposing a grid tied battery backup system that includes 22 355watt roof mounted panels (solar edge) a SE7600H
solar edge inverter and a solar edge 9.7KW battery and controller along with all necessary permits. I realize there are many variables involved here but that is the basic system for a price of 43K.
I am not expecting to run my whole house on this system but to draw from the battery backup and use the grid for additional power or to keep the battery system charged. I also have a 15K generac propane fired generator
any advice or opinions welcomed

jim naklick said:

22 355watt

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22x 355W x 4h = 31240Wh daily (hours will vary by season)

jim naklick said:

9.7KW battery

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9.7kWh (kilo watt hour)
31,240Wh / 9,700kWh = 3.22h to recharge from empty (with no loads, operating at 100%)

Have you done an energy audit to see how much power you use each day? And how much of that will be while the sun isn't shining (rough 20 hours a day)?

I suspect that during peak solar hours, you will have a large excess production at which time charging cars, doing laundry,... will benefit any self-consumption plan.

My neighbor has a similar system he had installed last year, but without battery (i tried!). That came in around $30k and a 10kWh battery would have been roughly $10k more. This included 200A service panel upgrade, EV charging station and micro inverters on all ~20 panels.

MisterSandals said:

22x 355W x 4h = 31240Wh daily (hours will vary by season)

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so the output of the panels uses a 4 hour window to determine that? would there not be at least some production outside of the 4 hour window?

MisterSandals said:

Have you done an energy audit to see how much power you use each day? And how much of that will be while the sun isn't shining (rough 20 hours a day)?

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I did do an energy audit although I did not take time of day load into consideration. IF grid tied is that still important to consider? I live in New York and as of right now the price paid per KW is the same price regardless of time of day

jim naklick said:

so the output of the panels uses a 4 hour window to determine that? would there not be at least some production outside of the 4 hour window?

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I am not sure of the exact methodology. I think the entire day is factored in.

Enter your exact data here to see the number of hours per month:

jim naklick said:

IF grid tied is that still important to consider?

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Its important if you want to self consume the power you generate. I suspect that during the day, if you have excess the utility may buy it from you for $.10/kWh and in the evening you may buy it back at $.20/kWh.

But if you store your excess daytime energy in your batteries and use it yourself in the evening, you'd essentially be paying significantly less for energy. Do you get charged for transmission fees (both ways?).

MisterSandals said:

But if you store your excess daytime energy in your batteries and use it yourself in the evening, you'd essentially be paying significantly less for energy. Do you get charged for transmission fees (both ways?).

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I'm not sure what you mean by being charged for transmission fees both ways? Do you mean that the power company could charge me to receive the excess power I generate? As I understand it, within New York the rates don't change by the hour but I can't say for sure that the power company would pay me the exact same amount either selling me power or buying it from me

I was originally planning a system with battery power supplying a critical loads panel that I would draw from all the time. If the solar wasn't enough then I would use the grid power (or my generator) to keep the batteries fully charged. The company I got the quote from said it was better to be grid tied to take advantage of rebates and sell excess power generated during the day back to the utility company.
would appreciate any opinions on this

jim naklick said:

I was originally planning a system with battery power supplying a critical loads panel that I would draw from all the time. If the solar wasn't enough then I would use the grid power (or my generator) to keep the batteries fully charged. The company I got the quote from said it was better to be grid tied to take advantage of rebates and sell excess power generated during the day back to the utility company.
would appreciate any opinions on this

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There's no reason you can't have batteries AND grid tie. With the way power companies are going, just selling your power will become longer and longer ROI's and still not work when the grid goes down.

Rednecktek said:

There's no reason you can't have batteries AND grid tie. With the way power companies are going, just selling your power will become longer and longer ROI's and still not work when the grid goes down.

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I posted this in another thread. I often realize that people don't realize why they have or want batteries.

I think we need to ask the question: Why batteries?

Let's list some reasons:
#1) To be completely off-grid
#2) To be able to have power when the grid goes down for short outage periods, say <=8 hours (on-grid)
#3) To be able to have limited power when the grid goes down for an extended period of time, days or months. (Limited off-grid)
#4) To buy or sell Utility power at a Time of Day when power is less/more expensive.

If your use case is #2), a generator (no batteries) may very well be a more cost effective solution.

If your use case is NOT #1, #3 or #4, you don't need batteries.

Let's say you have use case #4 and the batteries will cost you $10K. Depending upon the energy usage and the price difference, you may have a very long payback period.

Please don't get me wrong. I'm not saying batteries are not applicable. I'm saying you have to justify your individual requirements and make sure they make financial sense - unless you have extra money to throw away

I would be reluctant to consider Solar Edge, based on what I've read, and heard from installers.


I don't have reference prices for battery systems.

Grid-tie, I understand $2.85/W is average rooftop installation in the U.S. now.
I used to put the materials at $1.00/W, but probably about $1.25/W today due to RSD, and demand/supply chain.

You need to understand whatever tariffs and net metering terms you will get. And how well battery capacity helps you do better.

Also, know if it can start your loads. May be OK to run a well pump off generator occasionally, if you have a storage tank. A/C you want PV to be able to power.

Hedges said:

Also, know if it can start your loads. May be OK to run a well pump off generator occasionally, if you have a storage tank. A/C you want PV to be able to power.

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Ah, another use case for batteries: To supplement an undersized generator.
Missed that one

the reason I want a battery backup system is that I have no faith in the grid. I am not interested in trying to make money selling back to the utility company, nor do I plan (at this point) to be totally separate from the grid.
I guess I would qualify for "Think about its" #3
Again, not looking to run the entire house in the event of a grid down situation but to power critical loads
and while I do have a propane generator, I don't want to depend on it for any long term outage as now I am dependent on availability and cost of propane

No one makes money selling back to grid.
But, with a good net metering plan, the grid can serve as a battery. Doing this is much cheaper per kWh, has unlimited capacity, 100% efficiency, and zero discharge rate (except when reset to zero at true-up.)
You will probably get this with your SolarEdge system. Unless it is configured for zero export because net metering not available.

Net metering plan may cost $12/month connect fee. $144/year, think of that as same net-present cost as $1440 purchase of a battery.
For $1440 you get one 5kWh server rack battery. Net metering lets you bank a summer's production for winter use, about 3MWh.

Ideal PV/battery/inverter system will run your critical loads forever, start and run loads like A/C when the sun shines. Auto-start generator, use it to recharge battery, blend PV with generator or grid, limit current drawn from generator to programmed limit while supplementing from battery as needed. Use battery to time-shift power draw from grid.

Some inverters specify a generator larger than the inverter. Others can happily make use of a generator even 1/10th as big.
The various AIO and component systems will implement some but not others of the capabilities I named.

If you just buy whatever your vendor offers, you end up with whatever capabilities and limitations it has.

jim naklick said:

$43K.
I am not expecting to run my whole house on this system

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Those of us who DIY do expect to run whole house for that kind of money.
Hardware is maybe 1/3 to 1/2 of installed system. For GT PV, 1/3, but battery system would be more expensive hardware.
We might spend $10k to $25k to get what you're considering (plus a lot of sweat equity), and by selecting different hardware might get offgrid whole-house capability as well.


$9000 retail for that 9.7kW battery.

That would be well integrated with the SolarEdge system.
DIY people might buy a 5kW server rack battery for $1500, which is 1/3 the cost per kWh.
But many are having issues regarding surge capability and integration with inverter system.

MisterSandals said:

But if you store your excess daytime energy in your batteries and use it yourself in the evening, you'd essentially be paying significantly less for energy. Do you get charged for transmission fees (both ways?).

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I don't believe that's the case. In NY, they probably "settle up" once per year. If you produced more energy than you used, they pay you much less per KWh perhaps 5 cents. If you used more than you produce you pay the normal rate perhaps 17 cents per KWh. Those numbers include transmission fees.

I don't see any reason for him to have batteries other than to sustain a long term grid failure.

jim naklick said:

the company is proposing a grid tied battery backup system that includes 22 355watt roof mounted panels (solar edge) a SE7600H
solar edge inverter and a solar edge 9.7KW battery and controller along with all necessary permits. I realize there are many variables involved here but that is the basic system for a price of 43K.
I am not expecting to run my whole house on this system but to draw from the battery backup and use the grid for additional power or to keep the battery system charged. I also have a 15K generac propane fired generator
any advice or opinions welcomed

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Jim, let's forget what they are proposing. I had two of the largest companies give me proposals. Neither could give me an estimate of how much power I would actually be able to produce with their system. The system that I ultimately designed is far better than anything that they proposed.

There are a few numbers that we need. What is your annual KWh usage? What is your KWh usage for each month?

With that data we can do some calculations. The first of which is: What size system do you need to be completely off-grid and sustain you loads without shedding or critical loads? We use that as a baseline. You're probably going to find out that it's far too expensive or that don't have the real estate for the panels required. Bear in mind that during December, when the days are short, and often cloudy, you will have to generate and store enough power to satisfy the loads for several cloudy days.

Once we determine that a system calculated for off-grid will not work, then we need to work on a different strategy. One strategy could be to have a limited number of batteries and use the generator to supplement charging the batteries, keeping all loads.

The next strategy would be to use "critical loads" which you would have to list and calculate. You could size the system so that the PV and batteries could carry the critical loads, or you could size it so that the PV and batteries could carry your critical loads for a period of time and supplement that with a generator. One example would be that the PV and batteries could carry the loads in the Summer but not in the Winter.

Also, I would take the "proposed" system and punch it into PVWatts. (Google it). Please post the results.

Hedges said:

Net metering plan may cost $12/month

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Our Interconnect agreement is $40 a month just to have the grid regardless if you use power or not.
I didn’t sign up for it but that is the cost.

There is a forum member on here near me that pays $80 a month just to have the grid.
No usage included.

Nobodybusiness said:

Our Interconnect agreement is $40 a month just to have the grid regardless if you use power or not.
I didn’t sign up for it but that is the cost.

There is a forum member on here near me that pays $80 a month just to have the grid.
No usage included.

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That's usury, and should be illegal!

My water service is that bad ($70/month), but not my electric.
My mountain property, if I connected to the city water, years ago cost was $250/month (due to running a pipe up the hill after Loma Prieta earthquake tried up a spring.) Don't know the price today.
If they actually wanted us to conserve water, would have no flat monthly charge, just per gallon.
I pay so much to have a water meter that it would be a waste not to waste some.

My NEM 1.0 bill is $10.62/month. If I'm a net producer I get some dollars credited at true-up, which apply toward the monthly charges.
I have -$82 balance (a credit) with true-up a coming couple months after that statement. I think they give us some other credits during the year.

When I get pushed to NEM 2.0, some change to that charge.

Paying for pipes to a mountain property seems fair.
But only if my taxes do NOT pay for water systems supplying city dwellers.

Think About It said:

That's usury, and should be illegal!

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I do not disagree but if you want to net meter that is the cost.
They only pay avoided cost so .03-.04 KWh.

It’s honestly easier just to not tell them and do not backfeed any power.

They will complain but don’t really have a legal leg to stand on if you just Use power and not sell any.

Think About It said:

There are a few numbers that we need. What is your annual KWh usage? What is your KWh usage for each month?

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I have not been in the house for a full year yet but my usage for the last 9 months works out to be approx 900kw/month. One consideration is that I am planning on installing a heat pump water heater to replace my current elec model that has 4500 watt elements. Also I had to run a dehumidifier all last summer in my basement which I am hoping the new water heater will eliminate the need for that.
Again, I am not looking to run my entire house off the solar power - just critical loads (Which I have calculated but don't have that in front of my at this moment)

Think About It said:

The next strategy would be to use "critical loads" which you would have to list and calculate. You could size the system so that the PV and batteries could carry the critical loads, or you could size it so that the PV and batteries could carry your critical loads for a period of time and supplement that with a generator. One example would be that the PV and batteries could carry the loads in the Summer but not in the Winter.

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this is what I have in mind. My location is not the best for solar as I live in way upstate New York and in the woods enough that I will have to take shading from trees into consideration

My annual Radiation of 1.4 makes me cry.

it seems to me that being grid tied complicates the system for me? I am not interested in selling power back to the grid and doubt that given my situation/location/ panel array that I would be generating enough extra power that makes the additional equipment and permits necessary (not to consider that the power company will be charging me to sell them power). I am not at all interested in making money from this system but mostly want to be more self reliant.
I'm still learning but what would be the issue with having a battery backup of say 10K that would only power a critical loads panel and I would be drawing from that all the time. I have power from the grid that I could use to keep the batteries at full capacity (plus a 22k propane generator) when solar doesn't cut it. If there is unused power generated at peak times and it goes to waste then so be it.
Please enlighten me as to what is the downsides with my thought process?

That is what you want. Just have to find the best and most cost effective solution.

A grid-tied system with zero export could be the best balance between easy and effective. Nothing has to be powerful enough to supply your house, it is just a negative "load" that backfeeds your breaker panel. Current transformers ensure it doesn't backfeed grid, only puts in enough power for the house.

It, or another system, can provide battery backup to critical loads.

Here's a diagram from SMA that shows several degrees of implementation. It is similar to Tesla Powerwall.


Sunny Boy is PV inverter, backfeeds AC.

Sunny Boy Storage is battery inverter, can charge to store power which would otherwise be curtailed to prevent export. By itself, it can provide (manually switched) backup to small loads, while its charge holds out.

Automatic Backup Unit is a transfer switch (and auto-transformer) to disconnect from grid. Then, PV, battery, and house work together.

This system requires a separate meter to implement zero-export. Ideally, you select a hybrid which connects to current transformers.

SolArk is an all-in-one that connects to PV, 48V battery, current transformers, has generator input, and has transfer switch. Everything in one box.