Originally Posted by red-beard
As Z said, not trivial.
Lets talk a 4K system using 200Watt panels.
So you have 20 panels at $300 each = $6000 (Nominal 30V, Nominal 6.7A)
A 4K inverter = SMA Sunnyboy Grid Tie = $2000
2 rack of 10 panels or 4 Racks of 5 panels = $1000
Rack to roof ties = $400
Solar Cables = $200
2 x 30A DC disconnects on the Solar side $200 (I have a REALLY cheap source)
A couple hundred feet of 240V metal covered exterior cable and a couple of spare breakers - $500
Installation: Someone has to go on the roof and properly install the roof ties, assemble the panels to the racks, carry them up to the roof, install them, connect the cables, mount the inverter, install the disconnects, wire the inverter and disconnects, run the armored cable to the electrical panel, install the spare breakers and wire into the panel.
Roof work, here in Texas, about $2K. The electrical work, about $2K. On the west coast, a lot more.
IF my installation numbers are correct, the total is $14,300, or around $15K
This setup will produce 20-28kWh of electricty per day on a fixed roof. At my house, 20kWh costs $1.60. If you have TOD metering and you live in California where the electric company has to pay you the exact same rate you pay them for electricty, then you'll get .35/kWh which is $7-$10 per day. IF you can get $10/day, $15000 will pay back in about 5 years. With the Tax credit, this is reduced to 3 years. If there are local tax credits, it is even less.
For me? It takes about 18 years to pay it back...
With off grid, the batteries are about 60-80% of the cost of the system, to give you continuous power.
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