Solar and realistic expectations and perhaps a referral

[tortuga]

Actually I think it's been unclear from the OP if there exists or is a plan to bring utility power to the garage or not. There was mention of going the other way, i.e. bringing the solar/battery output to the house as a backup.

He wanted to at minimum supply the garage completely off solar and batteries but have an ability to switch the main house to solar via manual transfer switch also.

So there would be no possibility of grid power to the garage.
But he is installing a 100 foot feeder from the garage to the house.

Of course, it's impossible to say anything definitively without knowing rate schedules and interconnection and metering policies.

Yeah I think the business/economic model for these niche systems is a direct response to the cost of interconnecting with a utility added to the value of having backup power, as the grids get more unreliable than ever or just randomly shut off due to wild fire risk or whatever.

Look at all the treads we have on here about the cost of a utility transformer upgrade for a PV system to connect to the grid:
$21,000 transformer upgrade for PV
$20,000 transformer upgrade for PV
$3,200 transformer upgrade for PV

I wonder what the nationwide average cost for PV required transformer upgrades is?
Three is a bad sample size but averaging 15k that costs more than the proposed system,
then add the cost of a generator and you're ahead.

For a homeowner in a rural area with a old 10 kVA transformer, or on a lrge transformer but it shared with a neighbor whom has alredy maxed out its PV, it might be more economical to make a zero export system, than pay to upgrade a transformer.
Then there might be complex rules for zero export grid connected, so here we find people filling this niche.

Granted the transformer upgrade is a one time expense, generators need to be replaced about as often as the batteries will need to be replaced, so it might pencil out for the guy.

 

[ggunn]

So there would be no possibility of grid power to the garage.
But he is installing a 100 foot feeder from the garage to the house.

There is grid power to the house, isn't there? The feeder could also be used to power the garage, couldn't it?

 

[tortuga]

There is grid power to the house, isn't there? The feeder could also be used to power the garage, couldn't it?

Not if they connect it to a manual transfer switch like the OP said.

When i look up that system they have a nicer inverter available that looks like it can do zero export, he would have to pay more for the system though.
Say economics make the grid a no go for battery storage, either the 15k transformer upgrade was the issue or the utility wont let him export solar.
Would it not make more sense to run a regular feeder to the garage and set up a zero export system?
Then the house can use all the solar available.

 

[jaggedben]

There is grid power to the house, isn't there? The feeder could also be used to power the garage, couldn't it?

I'm struggling to envision how to set up the transfer switches so that one safely locks out the possibility of connecting the off-grid inverter output to the grid.

Also if there isn't already a feeder and you're going to install one, probably easy enough to install two.

 

[winnie]

Creating a bidirectional feeder with the utility at one end and a private source at the other end would require some sort of interlocked transfer switch arrangement.

But the person doing the installation is an industrial electrician. Maybe some Kirk Key interlocked switches are available at a good price

Jon

 

[tortuga]

Creating a bidirectional feeder with the utility at one end and a private source at the other end would require some sort of interlocked transfer switch arrangement.

But the person doing the installation is an industrial electrician. Maybe some Kirk Key interlocked switches are available at a good price

Jon

I could not determine if the other inverter on that website (that cost $1000 more) was indeed capable of zero export, but seemed like it. So if it was and the electrician can set it up for zero export, he could just have a bi-directional feeder, and the utility would none the wiser.. Probalby cost the same as the manual transfer switches or kirk keys, and use the full capability of the system.
EDIT: Oh wait he would still need the manual transfer switch at the service, well still it probably would pay for itself.

 

[tortuga]

And he would have to run a separate communications conduit to the service for the RS-485 or whatever the CT's need.