Owning Your Own PV System

[Hv&Lv]

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.

A common sales trick is to say something like,”you won’t need the power company”
Or “your power bill will go to 0”

It’s all a lie. You will always have a power bill. If you don’t ever use power again you will have the fee just to be connected and have a meter.
UNLESS! You go off grid.
Personally, I’m not tough enough nor knowledgeable for that type of living.

If it’s attached to the grid for export, then voltage following devices monitor the grid. When the power goes off, so do the inverters. Batteries can run some stuff in your house for a while.

 

[infinity]

UNLESS! You go off grid.
Personally, I’m not tough enough nor knowledgeable for that type of living.

If it’s attached to the grid for export, then voltage following devices monitor the grid. When the power goes off, so do the inverters. Batteries can run some stuff in your house for a while.

Off grid is not an option. The thought was in a prolonged outage the PV array would provide power and charge the batteries during the daylight hours. Are you saying that this type of system is not feasible?

 

[ggunn]

A common sales trick is to say something like,”you won’t need the power company”
Or “your power bill will go to 0”

It’s all a lie. You will always have a power bill. If you don’t ever use power again you will have the fee just to be connected and have a meter.
UNLESS! You go off grid.
Personally, I’m not tough enough nor knowledgeable for that type of living.

If it’s attached to the grid for export, then voltage following devices monitor the grid. When the power goes off, so do the inverters. Batteries can run some stuff in your house for a while.

Residential PV systems have changed dramatically over the last 10 years with the advent of more affordable Li ion batteries and spurred on by widespread power outages like the Snowpocalypse of 2021. The design manager for a local PV company told me a couple of weeks ago that nowadays half of the residential systems they are building include batteries.

Depending on the size of the batteries, the amount of connected PV, the weather, and the magnitude of the load being powered by the system during grid outages, it can be possible for such systems to run sustainably during an extended outage.

The down side of these newer systems is that unlike traditional grid tied PV, they are not simply "set it and forget it". They require that the customer understand how their system works. They need to monitor their battery usage and manage their loads so that they have power when they need it.

 

[electrofelon]

A common sales trick is to say something like,”you won’t need the power company”
Or “your power bill will go to 0”

It’s all a lie. You will always have a power bill. If you don’t ever use power again you will have the fee just to be connected and have a meter.
UNLESS! You go off grid.
Personally, I’m not tough enough nor knowledgeable for that type of living.

If it’s attached to the grid for export, then voltage following devices monitor the grid. When the power goes off, so do the inverters. Batteries can run some stuff in your house for a while.

Well actually, where I am you could have a zero bill. Annual surplus is given as a bill credit and will go toward the monthly service fee. I have enough of a surplus that I get about 5 months of a zero bill. But no it's not really cost effective to do that because the surplus is paid at a wholesale rate. You are best off meeting all your KWH and paying the monthly fee . Beats buying and maintaining batteries!

 

[Joe.B]

this type of system is not feasible?

I'm jumping in late, so I'm not answering for anybody else, but I just had a question for you. Are the big 4 appliances in the house gas or electric? If you're using gas for the high demand stuff, it's very feasible and affordable. The more electric appliances you want to use during an outage, the less affordable it becomes.

 

[infinity]

I'm jumping in late, so I'm not answering for anybody else, but I just had a question for you. Are the big 4 appliances in the house gas or electric? If you're using gas for the high demand stuff, it's very feasible and affordable. The more electric appliances you want to use during an outage, the less affordable it becomes.

All gas except for the wall oven.

 

[Joe.B]

A friend of mine recently got a Tesla battery installed. In his case it was basically free because he needs a CPAP machine at night and lives in an area that gets frequent outages. Most of his high demand appliances are gas. During an outage, if he's conservative with his use, he can last well over a week. Basically that means not running the laundry or dishwasher.

 

[Hv&Lv]

Off grid is not an option. The thought was in a prolonged outage the PV array would provide power and charge the batteries during the daylight hours. Are you saying that this type of system is not feasible?

Oh no, I’m not saying it’s not feasible. You simply have to size the system and batteries to your needs. I have had people call and say their solar isn’t working with full sun. In winter, and it snowed the night before. Have no clue why they can’t understand it when I tell them they have to clean the snow off the panels.
True story.. I had one lady ask why I wouldn’t send one of those “cherry pickers” to her house and have the guys clean her panels off.

 

[ggunn]

The down side of these newer systems is that unlike traditional grid tied PV, they are not simply "set it and forget it". They require that the customer understand how their system works. They need to monitor their battery usage and manage their loads so that they have power when they need it.

At a company I used to work for, a customer had spent a pretty large sum of money for a big PV system with multiple PowerWall batteries. One morning after an outage he called us yelling bloody murder about his system. He said that after sunset his system ran for only six hours before it shut down. His system was set up as a whole house backup, so we asked him what loads he was running the night it "failed". He told us (HVAC, lights, entertainment system, water heater, etc.) and after some quick calculations, we told him that yep, six hours was just about right. It wasn't the answer he was hoping for. He thought that with the backup running he could just keep on like he was still connected to the grid, although our salesman had gone through the system in great detail so that he would not have unreasonable expectations. Apparently he wasn't listening.

 

[electrofelon]

At a company I used to work for, a customer had spent a pretty large sum of money for a big PV system with multiple PowerWall batteries. One morning after an outage he called us yelling bloody murder about his system. He said that after sunset his system ran for only six hours before it shut down. His system was set up as a whole house backup, so we asked him what loads he was running the night it "failed". He told us (HVAC, lights, entertainment system, water heater, etc.) and after some quick calculations, we told him that yep, six hours was just about right. It wasn't the answer he was hoping for. He thought that with the backup running he could just keep on like he was still connected to the grid, although our salesman had gone through the system in great detail so that he would not have unreasonable expectations. Apparently he wasn't listening.

Yeah thats why I dont do off grid systems or battery back up stuff.

 

[shortcircuit2]

I own my PV system with no ESS. My system is 12KW on my average 8KW annual usage. In the 4KW over build I converted my fossil fuel HW heater to heat pump electric, so no my HW is free...well free once my system cost is paid off which I figure at 5 years. I also send 50% of my excess monthly production to my fathers electric bill and he realizes a monthly credit. My power company does not pay for the overproduction, but the excess sits in a bucket for the winter months when production is low.
The Federal 30% ITC is a big incentive as it reduces your federal tax burden $1 for $1. My power company also sends me a check every month for 10-years at .05 per KWH for my production. I have had no electric payment due since I turned the system on. I also considered an electric car in the future when planning the oversize system.
My only regret is not putting a system in when the incentives where bigger.

 

[ggunn]

My system is 12KW on my average 8KW annual usage.

I don't know what you mean by that. It looks like you are trying to compare kW to kWh.

 

[gadfly56]

I don't know what you mean by that. It looks like you are trying to compare kW to kWh.

I think he means his average draw is 8kW, but you really need to know your peak draw to determine if your system is large enough. That's why batteries or some other ESS are useful. You can buffer large draws via the ESS so you don't need to go crazy with your system size.

 

[jaggedben]

I'm jumping in late, so I'm not answering for anybody else, but I just had a question for you. Are the big 4 appliances in the house gas or electric? If you're using gas for the high demand stuff, it's very feasible and affordable. The more electric appliances you want to use during an outage, the less affordable it becomes.

"Less affordable" is a misleading oversimplification, in as much as:
1) $/w the cost tends to go down slightly for larger systems, so that's more affordable on a unit basis (Would you say the ketchup in a 24oz bottle for $5 is less affordable than in a 12oz bottle for $3.50?)
2) higher consumption doesn't force you to buy more solar, it just means you may only eliminate a portion of your bill.
3) if you can afford the upfront cost, then more savings long term is *more* affordable.

 

[jaggedben]

I think he means his average draw is 8kW, but you really need to know your peak draw to determine if your system is large enough. That's why batteries or some other ESS are useful. You can buffer large draws via the ESS so you don't need to go crazy with your system size.

That's not necessary on a typical net-metering tariff. On a net-billing tariff (like we have now in California), it is typically necessary in order to realize a portion of savings. So it depends on your state or local rules.

 

[gadfly56]

"Less affordable" is a misleading oversimplification, in as much as:
1) $/w the cost tends to go down slightly for larger systems, so that's more affordable on a unit basis (Would you say the ketchup in a 24oz for $5 is less affordable that the 12oz bottle for $3.50?)
2) higher consumption doesn't force you to buy more solar, it just means you may only eliminate a portion of your bill.
3) if you can afford the upfront cost, then more savings long term is *more* affordable.

1) Yes, if all you have in your pocket is $4.
2) True.
3) Maybe true. You need to take the time value of money into account and have a good guess as to future electric rates.

 

[jaggedben]

...
3) Maybe true. You need to take the time value of money into account and have a good guess as to future electric rates.

Sure, strictly speaking you need to do that, except that in my experience that always comes out positive. Actually the bigger issue IMO is predicting whether usage will grow, shrink, or essentially stay the same. That is, whether you'll miss out on the opportunity for additional savings, or pay for power you don't end up needing, or neither.

 

[wwhitney]

I think he means his average draw is 8kW,

8kW average would be 192 kWh/day or 70,000 kWh/year. Not plausible for a normal single family residence unless something is very wrong.

I believe what was meant was that an 8 kW PV system would be expected to annual generate about the full annual consumption at the time of PV installation, but a 12 kW PV system was installed. The rest of the post discusses how the excess generation was then utilized.

Cheers, Wayne

 

[electrofelon]

..well free once my system cost is paid off which I figure at 5 years.

Yeah that's about what mine was. Probably anyone doing it themselves and not counting their labor, would be around there for a simple payback. I have always been surprised that More sparky's don't put in solar.

the excess sits in a bucket for the winter months

Just a bucket of electrons sitting there in the garage....had the cat tip it over one time, man that took a like time to pick up, those things are small!

 

[ggunn]

8kW average would be 192 kWh/day or 70,000 kWh/year. Not plausible for a normal single family residence unless something is very wrong.

I believe what was meant was that an 8 kW PV system would be expected to annual generate about the full annual consumption at the time of PV installation, but a 12 kW PV system was installed. The rest of the post discusses how the excess generation was then utilized.

Maybe that's what he meant, but confusing kW with kWh is a pretty common source of confusion.