Hennessy and Palmer were determined to offset any electricity their home used with a batteryless grid-tied PV system. They turned to Mountain View Solar (MTVSolar) in nearby Berkeley Springs, West Virginia.
“With a new home, there’s always some guesswork involved in adequately sizing a PV system,” says Pablo del’Aguila, the crew lead/field engineer at MTVSolar. “We used the electricity bill from their old house and then made adjustments based on the new home’s specs. Based on the size of the house and the loads of the more efficient appliances, we came up with a conservative estimate.”
The guesswork paid off. The couple records daily system production data from the Enlighten website. Since its installation in July 2012, the system has produced more electricity than the home has used. Since November 2012, when the couple moved in, the 6.3 kW system has generated an average of 700 kWh per month, while the home consumed an average of 563 kWh per month. Thanks to the excess generation, the couple has never paid an electricity bill for the home. The microinverter-based system allows for module-level monitoring, making any future troubleshooting easier. An additional tie-in point was also added to accommodate system expansion.
With the exception of a propane cooktop and the wood-burning masonry heater, the home features all-electric appliances, including one of Hennessy’s favorite items—a Thermador steam and convection oven, which cooks food more efficiently with steam and reduces baking and roasting time compared to a conventional oven. “We cooked a 14-pound stuffed turkey about half the time (in 2.5 hours), and it was golden-brown and fabulously moist inside,” Hennessy says.
The PV system’s gross cost was $34,860, or $5.50 per watt. After rebates and incentives, the net cost was $14,402—$2.28 per watt. The couple benefited from a $10,458 federal tax credit and $4,000 state tax incentive (including a state tax credit for the 240-volt car charging station in the garage). The couple currently owns a Prius but does plan to buy a plug-in vehicle in the near future. “The state tax credit for the charging station was so good we couldn’t pass it up. It just seemed easier to install one during construction while the walls were opened up rather than to add it later,” Hennessy says. “We planned for the future.”