Standby Generator and Solar Installation in Hillsborough, NJ | Four Load Managers and 36 Panels

Hillsborough, NJ · Client since March 2013

Alan and Marcy in Hillsborough have been Green Sun Energy Services clients since March of 2013. The standby generator was commissioned that June and the solar array the following May.

A 17 kW machine in June 2013

The machine is a Generac 17 kW, model 6053-0, delivering 16 kW on natural gas, which is what this 3,000 square foot house runs on, behind a service-rated transfer switch.

What makes it worth writing up is what sits alongside it: four digital load managers. In 2013 that was an unusual amount of load management on a residential installation, and it is the reason a 17 kW machine was the right answer for a house whose full electrical calculation comes to 15,686 watts with air conditioning in it.

A load manager is a small device that watches one circuit and drops it when the generator is working hard, then restores it when there is room. Four of them means four separate decisions being made continuously rather than one blunt one, so the heavy loads take turns instead of competing — and the household experiences a house that simply works rather than a house that is rationing.

36 panels in May 2014

Thirty-six 250-watt panels, 9 kW in total, on Zep Solar mounting with an Enphase M215 microinverter behind each one. Estimated first-year production is 8,738 kWh and the utility is PSE&G.

Two hundred and fifty watts is what a panel produced in 2014, so nine kilowatts took thirty-six of them and a good deal of roof. A modern module does 435 watts; the same nine kilowatts today would be twenty-one panels.

Right-sized, not maximised

Both systems on this property are exercises in the same discipline, which is choosing the correct size rather than simply going as big as possible.

The array is bounded by the roof. There is only so much usable, unshaded, correctly oriented surface on any house, and panels added past that point produce less each year than the ones before them while costing the same to install and maintain.

The generator is bounded by something else entirely — not by what the house could theoretically draw, but by what it draws once four load managers have arranged for the heavy circuits to take turns. Without them this house would have needed a substantially larger machine, running well below its capacity for the twenty years between outages, burning more gas every week to exercise itself.

Neither system is impressive on paper and both are correct, which is the harder thing to sell and the better thing to own. The two do not overlap: the panels reduce what is bought from the grid across a year and shut down entirely the moment the utility fails, because a grid-tied array must not energise a line a crew is working on. The generator does nothing about the bill and everything about the days without supply.