Sanity Check - DIY 18kW System Costs

I need a sanity check with respect to costs of a DIY system. Assuming I am performing all the work myself. Costing, and sourcing panels, inverters, wiring, etc...

From project solar, they advertise $1.26 per Watt for a DIY install. It seems to be a decent price, but when I go out and quote 18kW of panels @$0.30/Watt, $2600 for grid tie inverters, $1k-$2k hardware (wire, breaker box, mounting hardware), I am calculating about $0.43/Watt after federal tax incentives. So what gives? Surely I'm missing something. I also cant seem to find this math being done by others. So I have a low confidence in it. Please feel free to beat me up


Heres my hardware lineup
45 x Hyperion 400w panels (HY-DH108P8B) - $5577
2x Growatt 10kW Grid-Tie Inverter - $ 2600
Hardware - $2000

Total = $ 10,177 ($7124 after incentive) or (0.395/Watt)

How do you plan to mount the panels? UL compliant racking system, which are almost certainly required to connect to the grid, are likely to cost as much or more than the panels. If mounting to the rooftop, you likely need per-module rapid shutdown, which will add $35-50/panel.

sunshine_eggo said:

How do you plan to mount the panels? UL compliant racking system, which are almost certainly required to connect to the grid, are likely to cost as much or more than the panels. If mounting to the rooftop, you likely need per-module rapid shutdown, which will add $35-50/panel.

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Roof mount. Asphalt shingles.

I was not expecting the need to implement a shutdown device per panel. Sounds like something big I was missing. thanks!

FLBuckeye said:

Roof mount. Asphalt shingles.

I was not expecting the need to implement a shutdown device per panel. Sounds like something big I was missing. thanks!

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NEC 2017 and on requires this. IIRC, if you use 60 cell panels (about 37Voc), you may be able to use one module per two panels. If shading is at all a concern, you can get Tigo optimizers that include the rapid shutdown function and kill two birds with one purchase.

You will likely need to use UL listed racking for roof mounting, or work up your own design and get it signed off by an engineer. Every time I've looked at it, it's been roughly the same price as the panels.

sunshine_eggo said:

NEC 2017 and on requires this. IIRC, if you use 60 cell panels (about 37Voc), you may be able to use one module per two panels. If shading is at all a concern, you can get Tigo optimizers that include the rapid shutdown function and kill two birds with one purchase.

You will likely need to use UL listed racking for roof mounting, or work up your own design and get it signed off by an engineer. Every time I've looked at it, it's been roughly the same price as the panels.

Click to expand...

My state (FL) is on NEC 2014 standards at the very least, so my original plan to have a shutoff further from the panel is feasible. Mounting system is not something I have thoroughly looked at. Only a handful of install diy videos. Mounting flashing/brackets with rails, and subsequent clamps did not originally look like a high dollar item.

FLBuckeye said:

My state (FL) is on NEC 2014 standards at the very least, so my original plan to have a shutoff further from the panel is feasible.

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My understanding is that FL is on NEC 2020, which has rapid shutdown requirements for building mounted solar panels.

NEC 2020 allows UL3741 systems (which don't need RSD per panel) if you can find equipment (rails, panels, inverter) that pass UL 3741 as a set.

FLBuckeye said:

Mounting flashing/brackets with rails, and subsequent clamps did not originally look like a high dollar item.

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Sadly, the rails plus RSD boxes can cost more than the panels.

Mike C.