Interconnection costs.approx costs

[mchhabria]

Thank you. I will try to size it down to use the size to fit a 11.4k solaredge or go even smaller. I am having no luck getting any answers from my local utility and the prices quotes for some things just make the whole project uneconomical.

Thank you for your reply.
Best

[max2k]

... 40A fits nicely into a 200A service using the 120% rule and that means a 7.6KW inverter fits nicely in a lot of designs I think.

it does - that's the way I went as well for the reasons you outlined

[tyab]

For load side - Square D has 70, 80, and 90 amp OCPD's. Heck Lowes and HD carry them.

The interconnect agreement posted by the OP makes it very clear that if you are to use Net Metering you have to use the two meter option. I guess their smart meter infrastructure is not up to date to allow single meter net metering. The posted yellow book gives examples of both load side and line side taps.

You are also required to provide a lockable disconnect switch. Your guy is just looking at the examples, and a 100 amp switch is only good up to a 60 amp OCPD. Your 13kw output will need a 70 amp OCPD so you are looking at a 200 amp switch. A GE general duty 200 amp switch from HD is about $300 so its not a deal breaker. For reference see NEC 705.12(D)(2)(3). If you do a line side tap you will want a fused disconnect - but the issue here is that disconnect will have to sized to match your service - so you are looking at a 400 amp disconnect (with 70 amp fuses). Those are starting to get expensive.

If you do a load side connect, your 320a service breaker is fine to use with a 70 amp backfed OCPD without any derating. If your service is a split 200/200 then the 200 that feeds the busbar you are connecting the 70 amp OCPD to will need to be derated to 150 amps. And the OCPD must be installed in the lower right corner of the panel. Again this should not be a big deal, it is common practice for electricians to keep that spot open even if the rest of the panel is full. If this is the case you will need to look at your historical use and make sure your peak usage does not exceed 36,000 watts to prevent nuisance tripping.

One way to hook up that 2nd 320a meter can would be with a Milbank 320 amp single position socket box. Something like a model U1797-O-K3L-K2L. They can be found in the $500 range if you look around. And at least 400MCM copper to hook that up. The key here is your existing service equipment on how hard/expensive that gets.

While that $3k bid seems high at first, so much depends on your existing equipment to determine what the real costs are going to be.

[max2k]

Thank you. I will try to size it down to use the size to fit a 11.4k solaredge or go even smaller. I am having no luck getting any answers from my local utility and the prices quotes for some things just make the whole project uneconomical.

Thank you for your reply.
Best

I think you need to review your project starting from:

1. what is your yearly consumption in kWh ?
2. what is your projected estimated consumption- are you going to add loads or the opposite- optimize them and actually reduce your consumption?
3. what PVWatts shows for your location/roof orientation?
4. at this point you'd have much better idea what size you need and if it's economically feasible or not.

By my rough estimate solar produces electricity at about 6-12 c / kWh given 20 year service life and SoCal location: at install cost of $3,200/kW and location- orientation specific rate of 1450 kWh/kW a year over period of 20 years you'd get 3,500 / (1450 * 20) = $0.11 / kWh . If your location or orientation is less optimal or if there's any maintenance/repair within that 20 year period the cost is even higher. SCE around here would gracefully buy excess from you at 4 c / kWh making it pure negative return investment for the part you oversize, it will never pay itself off. Most reasonable approach is to size it in such a way that you have some residual bill but at it's lowest price level. Here it is 12- 16 c / kWh and if it was flat rate I would never bother with solar.