Owning Your Own PV System

[infinity]

I'll preface this by saying that I know little about PV systems but I have some questions. Just about every time I'm in Lowe's or Home Depot the pushy, wandering solar salesman seems to find me. It got me thinking that the last thing that I would want is a long term contract with some third party company.

So for my needs I'm curious about installing a system that you would own outright with something like a battery backup for grid power failures. Do these exist? Also when sizing the system is it possible to have one that is large enough so that you really don't use very much of the grid power? A sparky told me that the POCO will not allow a system that is larger than your demand so that you're always buying some power from the POCO.

 

[winnie]

Totally possible to own your own system, and if you can swing the finances it is almost certainly more economical long term.

It probably doesn't make sense to have a battery large enough to avoid needing the grid; energy storage is expensive. In areas with a strong 'net metering' incentive you essentially use the grid as a free battery (there is a separate moral discussion to have on this point). In areas without this incentive it is usually cheaper to buy electricity than store it in a battery. So get the battery for backup purposes, not to avoid using the grid.

The utility restrictions on system size are tariff controlled and local.

 

[electrofelon]

We install systems all the time that meet all the energy needs of the client. Obvs this can vary widely, but often it's something like a 9kw system which is 20 450W modules. In NY, 25 KW is typically as big as you would go for residential for a number or reasons. If you make more than you use in a year, you will only get paid a wholesale rate for the excess.

Personally I would only own a system and not do one of these leases or contracts. Our systems are about a 10 year payback.

I don't think batteries are worth it, get a cheap generator. If you have time of use rates, that calculus may change.

 

[Dennis Alwon]

I have seen many homeowner's try and do it themselves. I don't believe it is all that difficult but homeowner's tend to buy cheap online modules and I suspect you get what you pay for. I am curious @electrofelon how long do your systems last. In the past the systems were not only outdated before the 10 years are up but they didn't last that long.

 

[electrofelon]

I have seen many homeowner's try and do it themselves. I don't believe it is all that difficult but homeowner's tend to buy cheap online modules and I suspect you get what you pay for. I am curious @electrofelon how long do your systems last. In the past the systems were not only outdated before the 10 years are up but they didn't last that long.

We warranty for the payback period, about 10 years. The modules and many inverters have much longer warranty than that. I'm curious, what happened to these systems that you said were outdated or didn't last? Modules are incredibly reliable and typically last for decades. Sure an inverter is a piece of electronics and they can fail. Enphase micros have a 25 year warranty.

 

[jaggedben]

You should absolutely own your own system if you can at all afford the upfront cost. Or get a loan from the usual sources (bank, credit union, HELOC) with transparent rates. The financing deals that some solar companies offer is usually expensive money. Often they also take the federal tax credit instead of letting you take it. Find a solar contractor who will do a cash purchase and doesn't push something else on you.

As far as I can tell New Jersey still has net-metering with an annual true-up, which means that any amount of solar whose annual production doesn't exceed your annual usage will be cost effective. And that whatever energy it produces, up to your annual usage, you are effectively not buying from the utility. But get a local knowledgeable person (not just some electrician) to confirm. The system size might be limited by your service or the utility, but that can be specific to you lr individual house.

Under net metering batteries are not necessary for saving money, and the goal of being independent of the utility is a bit of a vanity project. As far as backup for outages, the devil is in the details but systems certainly exist that can give you a decent amount of power in an outage at a reasonable cost. Consider it a luxury whose cost you consider separately from payback on solar.

Reasons not to DIY even if you are electrician:
- navigating the interconnection bureaucracy for a compliant interconnection and system design
- not causing your roof to leak
- lifting the panels to the roof
Unless you have buddies with experience.

 

[Dennis Alwon]

We warranty for the payback period, about 10 years. The modules and many inverters have much longer warranty than that. I'm curious, what happened to these systems that you said were outdated or didn't last? Modules are incredibly reliable and typically last for decades. Sure an inverter is a piece of electronics and they can fail. Enphase micros have a 25 year warranty.

I am talking about 20 years ago when solar was fairly new. It seems there were many issues with the system.

 

[Dennis Alwon]

We warranty for the payback period, about 10 years. The modules and many inverters have much longer warranty than that. I'm curious, what happened to these systems that you said were outdated or didn't last? Modules are incredibly reliable and typically last for decades. Sure an inverter is a piece of electronics and they can fail. Enphase micros have a 25 year warranty.

You are not saying that all modules are created equal, are you?

 

[jaggedben]

I am talking about 20 years ago when solar was fairly new. It seems there were many issues with the system.

Yeah that's an eon ago in solar. The industry completely revolutionized between about 2005-2010 and then the residential market did so again 2010-2015.

 

[jaggedben]

You are not saying that all modules are created equal, are you?

Within certain parameters, they kind of are. I mean, there are certainly some questionable no-name modules out there, but once you are out of that category then size and rating are pretty apples-to-apples. Good brands include Qcells, Silfab, REC.

 

[gadfly56]

If you have the space and exposure, would a ground mount system be the way to go?

 

[infinity]

The battery idea was just as a backup if we sustained a long outage like some parts of the country have experienced recently. I already have a portable backup generator with an inlet and an interlock but I don't see that as a long term solution if the power were to go out for several weeks. There's always the option of a whole house generator but if PV with battery backup is workable then taking the money that would be spent on the whole house generator system and using PV/Battery system instead seems like a better investment. My current electricity usage is about $3000/year so just a PV system with a 10 payback wouldn't be worth the effort because I don't plan on living here that long.

If you have the space and exposure, would a ground mount system be the way to go?

My roof exposure is somewhat favorable for PV. I have far too many trees for a ground based system.

 

[winnie]

If you have the space and exposure, would a ground mount system be the way to go?

IMHO, yes. Ground mount removes the issues of worrying about roof leaks and rapid shutdown to protect home occupants.

I am strongly considering a 'solar pergola' for my home. This is essentially an elevated ground mount system, where the solar panels become the roof of a shade structure for outdoor enjoyment. The downside of such is that now you are paying for the structure.

I believe @electrofelon has an interesting hybrid where the solar array was designed as the roof structure for an outdoor storage building.

-Jonathan

 

[winnie]

One of the downsides of using a generator as backup for a grid interactive PV system, is that when the grid goes down the PV system also shuts down, and the PV system will not play nice with the generator.

Having a _small_ battery often steps the inverter up to a system which can run (and use PV) even when the grid is down. This could significantly reduce the burden on a generator in a long duration outage.

-Jonathan

 

[ggunn]

One of the downsides of using a generator as backup for a grid interactive PV system, is that when the grid goes down the PV system also shuts down, and the PV system will not play nice with the generator.

That isn't necessarily true; there are systems that will allow integration of PV, batteries, and a generator. They are not as common as straight grid tied PV or PV with batteries where you have to separate the PV from the generator, but it is possible although it is expensive.

 

[analog8484]

One of the downsides of using a generator as backup for a grid interactive PV system, is that when the grid goes down the PV system also shuts down, and the PV system will not play nice with the generator.

This is true for traditional grid-tied inverters but newer inverters like the Enphase iQ8 is supposed to able to work with generators. The way I understand it is that it switches to grid forming mode during grid outages and is able to parallel with qualified generators, kinda of like generators that can parallel with other generators.

 

[winnie]

It makes sense that at least some inverters will work with some generators; there is no physics reason that such systems cannot work, but rather a controls issue.

The _problem_ is that traditional grid tied inverters are designed to export excess power to the grid and generators are only designed to export power, and cannot deal with absorbing power from the PV system. With proper controls, the system could be designed so that the generator is never expected to absorb power.

During a discussion of this point some years ago, the consensus was that companies would not think it worth the effort to design compatible systems, but I guess enough customers asked for this feature that it became a selling point. Thanks for the update!

-Jonathan

 

[ggunn]

It makes sense that at least some inverters will work with some generators; there is no physics reason that such systems cannot work, but rather a controls issue.

The _problem_ is that traditional grid tied inverters are designed to export excess power to the grid and generators are only designed to export power, and cannot deal with absorbing power from the PV system. With proper controls, the system could be designed so that the generator is never expected to absorb power.

During a discussion of this point some years ago, the consensus was that companies would not think it worth the effort to design compatible systems, but I guess enough customers asked for this feature that it became a selling point. Thanks for the update!

-Jonathan

The crux of the biscuit is that there must be safeguards in place to prevent PV from backfeeding the generator, and it can be done. Whether it makes economical sense to buy a system which will allow the PV to run while it is islanding (running off grid) during a power outage with a generator is another question. If power outages are of short duration, then it may not be worth the expense.

 

[electrofelon]

You are not saying that all modules are created equal, are you?

I agree with Ben, they sorta are. Bed/defective modules seem to be very rare in my experience. I've never really had or heard of problems even with the less common manufacturers. I care very little about the manufacturer when shopping for modules, it's mainly about the size and power I need and the price. Imean I'm sure there is probably stuff on Amazon that I would be skeptical of, but I think those are often smaller modules and not the kind you would use on a grid tie solar system anyway.