Jerry Walsh-Skelly writes: We connected the net-meter
system on Oct. 22, 2009, and tracked our power purchase
and sale for the winter months, November 2009 through
February. Here’s what we got, effective March 9:
Bought from Louisville Gas & Electric (LG&E): 1,757 k Wh
Sold back to LG&E: 614 k Wh
Net purchase since Oct. 22, 2009: 1,143 k Wh
Average daily power purchase: 8. 23 k Wh
At 7. 3 cents per kilowatt-hour: 60 cents per day
When Kerry and Jerry Walsh- Skelly, both lawyers, decided to drop out of the Washing- ton, D.C., rat race in 1993,
they settled on Louisville, Ky. They bought a
1937 brick Colonial-style house on the edge of
a historic district and settled in. Kerry went to
work for a distillery (today she’s global marketing manager for a well-known brand of bourbon), and Jerry began teaching language arts
and social studies at an inner-city school.
The old house was drafty. During a renovation in 2001, the Walsh-Skellys found no insulation in the walls, only old newspaper wrapped around
some hot-water pipes. They installed fiberglass batting in the exterior walls
and upgraded to insulated windows. But a full energy audit, with a blower
door, showed the envelope still leaking badly. a thermographic camera
showed just where those leaks were. They hired a contractor to blow in extra
insulation and seal all remaining leaks with grout and caulk.
Electricity is cheap in coal-burning Kentucky — about 7. 3 cents per
kilowatt-hour now, but it was just 4 cents in the mid-’90s. Jerry had lived in
Europe and seen what was possible in home efficiency, and he liked the idea,
in principle, of zeroing out the utility bill. It wasn’t a matter of money, Jerry
said, so much as a green and renewable sense of responsibility.
and so, in preparation for putting up a photovoltaic (PV) system, the
Walsh-Skellys went on an energy diet. They removed every incandescent
lamp in the house, installing LEDs and CFLs instead. Exterior lights were
replaced with solar-powered LED units. They bought a Kill a Watt power
meter and got rid of all their phantom loads. They even bought a laundry
spinner to cut the power draw on their dryer.
Finally, in 2009, it was time to plan out the PV system. “It was the 30
percent federal tax credit that made it practical,” Jerry said. Sensitive to the
neighboring historic district, the Walsh-Skellys wanted a roofing-integrated
array — something that would be innocuous, if not invisible, when viewed
from the street. This was especially important because the street-facing side
of the roof is the south-facing surface.
Enter Dan Hofmann. Like the Walsh-Skellys, Hofmann was a refugee
from the corporate rat-race. In 2008, he’d spent enough time as a data
analyst for a health-insurance company for one lifetime and wanted his
own hands-on business. He took the online course in PV design with Solar
Energy International ( solarenergy.org) and signed up Heritage Electric
( yourheritageelectric.com), a local contractor, to run his wiring. In March
2009, Hofmann launched RegenEn Solar ( regenensolar.com).
Hofmann initially put together a quote for crystalline panels, but when
Kerry explained the aesthetic issue, he ran numbers for thin film. “after
looking at all of the energy-efficiency upgrades, we thought that the Uni-Solar amorphous silicon would be able to do the offset needed to make the
project economic,” Hofmann said. He also looked for local examples of the
technology in use and couldn’t find another grid-tied thin-film system in
the state. He thinks this one may be the first.
Working with Chan Cornett of Cornett Roofing in Indianapolis (cor
nettroofing.com), Hofmann figured out that a Uni-Solar thin-film array
applied to standing-seam metal roofing would meet the Walsh-Skelly
architectural requirements. He designed a 2.7-kilowatt array using 26
18-foot ( 5.5-meter) modules, each about
16 inches ( 40 cm) wide and producing 144
watts in full sun. Each module is wired to its
own Enphase microinverter. Cornett built
a custom ridge cap to accommodate the
wiring and microinverters. During installation in September, Hofmann worked on
the ground, affixing the pre-glued modules
to the steel pans before sending them up to
Cornett’s crew on the roof.
The roof is pitched 33 degrees from horizontal, a close match to Louisville’s 38-degree latitude, and azimuth is nearly
true south, which provides maximum solar gain. The new metal roof cost
about $10,000, and the PV system cost about $20,000. after tax rebates, the
bottom line was about $23,000.
By early October, the system was cranking out up to 19 kilowatt-hours
(k Wh) of power daily, measured by the Enphase Enlighten web-based
logger (for real-time Walsh-Skelly data, see enlighten.enphaseenergy.com/
public/systems/c73M1445). Hofmann calculated that the Walsh-Skellys
could sell their renewable energy credits (RECs) for about $1,000 a year
(at 2009 rates) and with net metering, the project should reach payback in
about 10 years.
Jerry calculates that differently. He figures that the REC price could
drop and that electric rates are unpredictable. He’d be happy with a 15-year
payback but says that swings in pricing could make it as short as seven years
or as long as 20.
Meanwhile, he’s happy with the look of the system. a realtor who lives
nearby jogged by one day and stopped to admire the new roof. When Jerry
said, “It’s solar,” she was startled.
“you’ve increased the value of the house significantly,” she told him.
Recalculating the higher home value against the initial cost and the net-metered production, Hofmann figured the system is earning a 7 percent
annual return on investment and will achieve payback in about seven years,
depending on the future price of electricity.
Jerry doesn’t care about that. He and Kerry expect to live in this house
He does care about power production and monitors it daily. Electrical
use has dropped sharply. In the four months ending Feb. 12, the house
drew 1,082 k Wh, down 70 percent from the 3,592 k Wh used in the same
period a year earlier, and the electric bill has averaged about $16 per month,
including a $5 per month connection charge. Over the same period, natural
gas used for water heating, cooking and space heating fell 26 percent, from
61,900 cubic feet (1,753 cubic meters) to 45,500 cubic feet (1,288 cubic
meters) — very good for a 2,800 square-foot (260 square-meter) house.
“and it’s been a really cold winter,” Jerry said.
Now he’s eager to see what the PV system will do in mid-summer. “We
try to go easy on air conditioning,” he said. “We try not to turn it on at all
until July. But the roof should produce about 30 k Wh on a good summer
day, so I’m hoping we’ll offset all of the summer load.”
“The wonderful thing about this is that the neighbors love it,” Jerry said.
“They know the system works and want to see the energy bills and have
absolutely no issues with the way the roof fits in with the historic nature of
the nearby houses.” S T