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Installing a PV system on the roof is certainly one way for homeowners to
address energy costs and dependency. Photovoltaic cells convert solar energy
into electricity (DC voltage) with efficiencies that range from eight to 12
percent (for details on how PV cells work, visit www.norcalsolar.org/FAQ/faq.html). They are mounted in
groups, typically in large, flat panels several feet across. Connecting cables
tie the panels to an inverter, a device that converts the DC current into AC,
which is what is used by residential appliances and lights. The inverter ties
into the circuit box, and when the sun is shining, some or even all of a home's
electrical needs can be met by the PV system.
According to Bob Reid of Reid Heating & Energy (shown at right with a solar
panel), a Marin county installer of photovoltaic systems, the state rebate
program is a "powerful incentive driving much of the interest in solar power"
for residences. The California Energy Commission offers cash rebates on eligible
renewable energy electric-generating systems through the Emerging Renewables
Buydown Program (details at www.consumerenergycenter.org/buydown/program.html). In
the past, rebate funds have been set at $4,500 per kilowatt, or 50 percent of
the system purchase price (whichever is less). However, due to strong demand,
the state's available rebate funds have been running out before the end of the
year.
It is also possible, speculates Andy Black of Eco Energies in Palo Alto, that in
the future the state "will lower the rebate from $4.50 to $3 or $3.50/watt". He
and other solar advocates are not concerned about the looming $20 billion plus
state budget deficit and how it might impact the solar rebate program. Still,
homeowners would be wise to have a guaranteed rebate commitment in hand before
starting a solar installation, according to Reid. And California program
administrator Timothy N. Tutt stated in a New York Times report last November,
"We think we have sufficient funds to match the demand over the next five years,
but who knows, it might go faster than that."
Criteria to qualify for a rebate include: the system cannot produce more than
200 percent of the site's historic or current energy needs; if a homeowner
installs the system him- or herself, the labor does not count as a system cost;
and the system must be connected to the electrical utility grid.
Before making a decision on a PV system, Reid recommends that homeowners first
carefully consider how they can reduce their energy needs. "It's like preparing
for a marathon," he said. "You need to get in shape first." Reid claims
switching to energy efficient lights and appliances — a good idea in any
case — can reduce the size of the PV system required (learn more at www.consumerenergycenter.org/homeandwork).
The ability of a PV system to reduce monthly electric bills depends of course on
the size of the system (how many watts it generates) and how many watts are
demanded of it at any one time. For an average-sized Eichler — certainly
not a large house by current standards — a one to three kW (1,000 to 3,000
watts) system is recommended by most solar installers.
Cooperative Community Energy, a renewable energy co-op based in Marin County,
recently performed a detailed equipment analysis for our purposes. The Eichler
under scrutiny was a 1,600-square-foot home that had an average monthly electric
usage of 513kWh (equal to approximately a $70 monthly bill). Cooperative
proposed a system comprising 24 panels mounted flush on the pitched section of
the roof (not visible from the street) that would produce approximately 2.4kW of
power, supplying approximately 75 percent of the home's daily electrical usage.
For many homeowners, system costs prompt the obvious question: "How many years
until the system pays for itself? A newly installed PV system starts saving the
owner money on their electric bill right away, but that system can cost $20,000
to $30,000, or more. The California state rebate program (which the state
legislature recently extended for an additional ten years) and 15 percent solar
tax credit brings the actual cost far below the retail price tag, to about 50
percent of the purchase price.
However, calculating a payback scenario for the cost of a PV system is rather
complex. Simply dividing the system cost by the estimated yearly savings does
not take into account system depreciation, loan costs (or if a loan was not
required, the cost of money), pre-tax cash flow, inflation, future electrical
rate increases (which no one can predict accurately), and other variables.
EcoEnergies' Andy Black has produced a detailed financial analysis, including a
payback schedule. Black's study showed that a 2.1kW system could reduce monthly
electricity charges by $67. If a home uses approximately 500kWh per month, the
monthly bill would nearly be fully covered. If the monthly bill were closer to
700kWh per month, a 2.9kW system would be needed to achieve the same results.
(This assumes the system is positioned properly on the roof and it receives a
certain number of 'peak sun hours' based on historical weather patterns in the
Bay Area.) Black's analysis predicted an 8.1 to 9.4 year payback duration for
2.1kW and 2.9kW systems costing (after rebates and credits) $13,800 and $17,400,
respectively. After recoupment, the systems will produce a savings of $67 to
$100 per month. (Note: these figures don't apply to Palo Alto residents, who pay
less for electricity than the rest of the Bay Area)
So why hasn't this compelling scenario resulted in thousands of Bay Area roofs
sheathed in glistening blue solar panels?
For starters, even an eight-year recoupment period can seem far down the road
for many homeowners. In addition, Americans move regularly, and some may
calculate that they won't be in their homes long enough to reap the benefits.
It is also not clear if PV panels on the roof add to a home's value, though
EcoEnergies'Black quotes from an article in a real estate appraisal publication
which claims that every dollar of reduction in utility bills adds $10 to $20 to
the value of the home (note: the article does not specifically discuss solar
systems). Cooperative Community Energy's Steven Traiger argues that, "Most if
not all the cost would be included in the price of the home plus the savings
that the homeowners saved for the number of years that they used the home", so
that it doesn't matter what the payback time is.
While some buyers may consider solar power a positive, others may be intimidated
by technology they don't understand and don't want to maintain — even
though most solar-panel manufacturers claim the only maintenance required is
periodic cleaning (the same way one washes windows) and that systems failures
are rare (there are no moving parts). Nonetheless, the EcoEnergies analysis
factors in yearly maintenance costs of approximately $100.
Cooperative Community Energy did not provide their version of a payback analysis
by press time, but Traiger did offer a glimpse into their payback picture when
he pointed out, "I have found that if the monthly bill is under a $100 a month,
not only is the payback a large number of years, it's not justifiable to spend a
large amount of money to offset your bill by a small amount, even if it adds
value to the home."
Given the lengthy payback times, the issue of system warranties also becomes a
critical one. Most solar-panel manufacturers offer 20- to 25-year limited
warranties that typically provide full replacement if the panel output falls
below 80 to 90 percent of normal (depending on manufacturer specs). The panels
are by far the most costly part of the system. The next highest price tag is
attached to the inverter, which EcoEnergies indicates will typically last 15 to
20 years before needing replacement (which is beyond the 5-year warranty).
Homeowners can attempt to accelerate their system payback time by purchasing a
system that will generate enough juice to feed energy back into the grid and
further reduce electric bills. The California Net Metering Program requires
electrical utilities to credit all electricity generated by a customer-owned
solar or wind system against the customer's usage of electricity sold by the
utility. To do this, a special 'smart meter' is required (at a cost of about
$300). This meter features the capability of being able to run backwards, a
rather bizarre sight to behold.
In addition, a smart meter can adjust for juice produced during peak rate hours
(most daytime hours) further boosting credits accumulated. However, careful
calculations need to be performed by every prospective PV purchaser to determine
if a larger system that will spin the meter in reverse can be cost-justified.
Again, it all comes back to making the home as energy efficient as possible at
the onset.
How the panels mount to the roof is yet another concern, both in terms of the
integrity of the roof and the aesthetic impact. Visually, solar panels can
potentially be a problem, as they work best when positioned approximately 38
degrees off the roof. Selecting a location towards the rear of the house can
mitigate the aesthetic impact, at least from the street perspective.
When it comes to attaching the panels to the roof, Reid Heating & Energy's
Bob Reid indicates that "the ideal time to install solar is when it's time for a
new roof anyway. But if the roof is in good shape, I work closely with the
roofer to make sure it's done right." He prefers to attach the mounting brackets
to those massive Eichler beams,  and then brings in the roofer to seal around them. He
remains skeptical of the durability of systems mounted with guy wires attached
to roof fascia or beam ends. When dealing with an existing roof, he coordinates
closely with the roofer on sealing the penetrations, and claims this typically
adds only about $500 to the total system cost.
Homeowners should obtain coverage in writing that specifies the company (or
companies) who will be responsible in the event of future leaks. If at all
possible, it may be best to bring in the same company that originally installed
the roof to seal the new penetrations, thereby avoiding future finger pointing.
EcoEnergies states that they cover any roof leaks around their installations.
Still, determining the origin of a leak, if one or more should arise, can be
problematic.
Systems such as the Powerlight 'PowerGuard®' and an upcoming product from
Schott Applied Power avoid roof penetrations entirely, but according to
Cooperative's Traiger, neither company sells systems scaled to residential
installations. EcoEnergies' Black says both are a viable alternative for the
Eichler owner, even though the modular tiles are limited to roof pitches up to
nine degrees (just under the classic Eichler 2:12 pitch of slightly over 9
degrees). The tiles lay flat on the roof and incorporate a 'perimeter curbing'
ballast that the manufacturer claims enables them to stay in position even when
buffeted by winds, as much as 140mph, they claim.
While undeniably attractive in concept, one can question whether a large area of
such tiles on a flat Eichler roof might impede drainage once a single winter's
season of leaves and detritus fills the small gaps beneath the tiles (no flat
roof is perfectly flat). Black claims that Powerlight "does not allow it to be
installed over any roof ponding (over one foot in diameter, roughly) because of
the detrimental effect the longer drying period would have." Still, it bears
keeping in mind that standing water is the enemy of every roofing surface.
Whatever type of panel is selected, these "grid-tied" systems do not provide
power if the grid goes down, since state law requires them to automatically shut
off. If that result is not desired, a different type of inverter, and "deep
cycle" batteries (typically lead acid or sealed gel) can be connected to the
system, though that hardware won't qualify for the state rebate and the total
system cost is several thousand dollars more than a standard system. Battery
lifetimes run 5-10 years, and they can be recycled. Normally this type of solar
system is designed so that the batteries are only drawn on when the grid is down
— if they were used nightly the battery life would be much shorter.
What does the future hold for solar power in the residential arena? Although PV
technology is decades old, there is still potential for improvement. In the
lab, photovoltaic cell efficiencies have been measured at over 20 percent, while
commercially available systems do not exceed 12 to 14 percent. The
more-efficient systems may not come to market until there is more demand, as
they are more costly and will require large-scale production to bring prices
down. Regardless, says Bob Reid, "No one should wait to install PV just because
it might get better. It's very good right now."
Ultimately, solar power may be used to produce hydrogen gas to power fuel cells,
which then will be able to generate electricity for home use. But that move is
possibly decades away. The decision of whether or not to invest in a residential
solar system is ultimately a matter of balancing a multitude of factors. For
some, just the satisfaction of increased energy independence and making a
positive contribution towards environmental quality may be all that's needed to
propel them into a PV purchase. Others may be convinced by the long-term
financial payoff (which only works as long as the state keeps providing generous
rebates).
At the moment, though, it seems that for many homeowners, the initial cost is
intimidating, and the payback realization too far down the line. A neighborhood
of shiny blue roofs doesn't appear likely any time soon — at least not
without a serious push from the federal government, perhaps an unlikely event
under Washington's current administration.
Learn more at:
www.norcalsolar.org
www.consumerenergycenter.org
www.cooperativecommunityenergy.com
www.ecoenergies.com
See other Eichler House Doctor stories
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