Roof, Solar and Generator in Princeton, NJ | 17.02 kW Array and 26 kW Backup

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37-panel 17.02 kW solar array in Princeton, NJ by Green Sun Energy Services.

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Princeton, NJ · Client since January 2025

Mohamad from Princeton, NJ has been a Green Sun Energy Services client since January of 2025, when he bought all three trades on a single day. What the house needed was not simply a new array – it already had one, sitting on a roof that had reached the end of its life.

The array that had to come off first

There is no way to reroof a house underneath a live solar array. The panels are fastened through the roof they sit on, so the existing system was taken down before the roofers arrived and the deck was handed over bare. That is the expensive lesson this page exists to record: an array installed onto shingles near the end of their life does not save the cost of a roof. It defers the roof, and adds the removal of the array to the bill – and what goes back up afterwards is a new system, not the old panels dusted off and rehung.

6,100 square feet of new roof

Finished on 10 March. A single layer stripped to the sheathing and carted away, then 6,100 square feet of GAF Timberline HDZ in weathered wood, warranted fifty years, with continuous soffit vents at the intake. At 6,100 square feet this is a large roof, and the area is what makes the order of these jobs matter so much: every one of those costs scales with it.

A 26 kW Generac

Four days later. A Generac rated 22.5 kW on natural gas – 26 kW on propane – behind a 200-amp managed whole-house transfer switch with two load-management modules and whole-house surge protection. The load survey explains the size: 4,200 square feet, a well pump, an electric oven, a sump pump, two refrigerators, a separate freezer, a dishwasher, a washer and a gas dryer. A well pump and an electric oven in the same house is a demanding pair – the pump is a motor load that surges every time it starts, the oven a large steady draw, and on a well an outage means no water at all until the machine picks the house up.

37 panels and 17.02 kW, on a bare deck

Live on 20 March: 37 REC 460-watt modules on a SolarEdge HD Wave inverter, spread across four roof faces at 7.36, 4.14, 3.22 and 2.30 kW and estimated at 20,787 kilowatt hours in the first year. This is a new system rather than the old one refitted, designed for the roof that now exists rather than adapted to the mounting that used to be there. Seventeen kilowatts across four orientations is precisely why it wants per-panel electronics: four faces give four production curves through the day, and without optimizers the weakest would set the pace for whatever it shares a string with.

Ten days, and the order nobody gets to skip

Remove, reroof, replace – and a generator in the middle of it. The reason this house went through all of that in ten days is that the roof underneath its original array had run out, and there is no version of that story where the panels stay up. Doing it in one run at least meant it was done once: one crew, one load calculation covering a house about to gain both a standby generator and seventeen kilowatts of solar, and a new array designed for a roof with fifty years ahead of it rather than fitted to one already behind. The next time this roof needs attention, nobody alive today will be scheduling it.