Birds tweet and scatter at the approach of the automobiles. Early morning sunshine cuts slantwise through the dense trees and bathes the roof of a single-story home with light.
"Installers have arrived," announces homeowner Bob Kovacs as a white utility van and a dark pickup truck roll up to his one-story home in the Blue Ridge Mountains of Virginia. Kovacs is an engineer, author, and self-described solar enthusiast.
The date is June 21, the Summer Solstice, a fitting occasion for the installation of an 18-panel, 4.2-kilowatt energy system dedicated to turning summer sunshine (and fall, winter, and spring sunshine) into household power.
Two men wearing rubber-soled shoes step gingerly along the shingled rooftop, screwing in flanges. The metal "tents" you see nearby are aluminum deflectors waiting to be flipped over and glued in place above each flange to keep rainwater from flowing between the flange and the shingles.
"This is all going very quickly," says Kovacs as a worker lays down the last of the rails across the mounting flanges. "The crew has been here only about half an hour and already the mounting flanges and rails are on the roof." Each rail is comprised of two pieces, which get sandwiched together with self-tapping bolts. Then the rails are mounted to the flanges.
About an hour later, the crew is ready to install the power inverters and run the related wires along the roof.
Kovacs' system is distinguished by its use of a microinverter beneath each solar panel instead of all the panels feeding into a central inverter.
What does the inverter do?
Photovoltaic (PV) panels convert the sun's energy into DC power, but households run on AC power. Every solar panel system needs some point of inversion to flip DC into AC. Kovacs opted for small inverters—microinverters—one beneath each PV panel. Alternately, panels could be strung together like Christmas lights to feed into one central invertor, often called a string inverter, that is kept in, say, the garage or even outdoors.
As the workers lower another one of the 18 panels in place, connect the wires, and fasten the bolts, Kovacs is pleased with the progress. "It's been less than two hours since they've been here, and most of the panels are on the roof. There's still plenty of installation left to do, but that's a pretty good sign." Each panel generates 235 watts; multiply that by 18 and you have a 4.2-kw system.
On the second day of installation comes the electrical work, which starts with an electrician carefully assessing the home's current setup. Details that had been gathered prior in the system's planning sessions are now confirmed. Workers begin cutting and bending conduits.
Inside the garage, the electrician mounts an interconnect breaker. This device ensures that the house draws on solar power first, with the power grid as backup. Interconnection also permits excess electricity to flow to the grid.
Is interconnection the same as net metering?
They are related but separate. Interconnection describes how a home solar energy system is hooked up to the utility and vice versa. It's an INTERconnection: it goes both ways. Many states have good interconnection standards, which helps ensure the quality of the hookup.
Those states also tend to have good net metering laws because net metering relies on high-quality tracking of the electricity flowing in and out of the home. The electricity you draw from the utility is offset by the excess you send to the utility, and you pay only for the net, or difference.
Virginia offers net metering for residential systems up to 20 kW, ensuring that Kovacs and other solar energy producers are paid fairly for the power they contribute to the grid.
On this second day of the installation, the whole job is over in four to five hours. Kovacs says the crews were "fast, neat, and professional."
A particularly satisfying moment of the installation comes when Kovacs watches the meter on the side of the house start to run backwards.
"There you go!" says the electrician. "The meter's now spinning backwards."
Kovacs says, "If you add all these things up, the system will pay for itself in five years."
- Total cost of system (labor and equipment): $31,265
- Tree removal to maximize sunlight: $4,000
- Federal tax credit (30% at the time): -$9,380
- State solar rebate: -$7,120
- Final cost: $18,765
- Solar renewable energy credits (SRECs): $800/year
- Electricity savings: $400-$700/year
- Property value increase (est.): $10,000
Kovacs recorded and edited the installation and shared the video on YouTube. Watch here.