We know that going solar is a tricky subject and no matter how much research you do there are always more questions. Our customers and users know that they can look to us for the best info. Mainly because Real Goods has been in business for so long we've seen it all!
Solar Answers
Can state rebate incentives take a chunk out of the cost of going solar? — Melanie C., Frisco, CA
Go to www.dsireusa.org to find out what grants or incentives area available in your state. For instance, in California you can multiply your gross installed cost by 0.65 to account for rebates and tax credits. In New York or New Jersey multiply by 0.5.
What will it cost for me to go solar? — John H., Santa Monica, CA
This answer is never easy as so many factors can come into play. The only real way to get an exact cost is to schedule a visit from a solar installer. You can however click here to visit our estimator page to enter some simple information and have your estimated cost to install including any rebates and credits calculated for you!
What are photovoltaic cells? — Justin K., Denver, CO
Photovoltaic cells were developed at Bell Laboratories in the early 1950s as a spinoff of transistor technology. Very thin layers of pure silicon are impregnated with tiny amounts of other elements. When exposed to sunlight, small amounts of electricity are produced. They were mainly a laboratory curiosity until the advent of spaceflight in the 1950s, when they were found to be an efficient and long-lived, although staggeringly expensive, power source for satellites. Also, the utility companies couldn’t figure out how to get their wires out into space, so PV was really the only option! Since the early ’60s, PV cells have slowly but steadily come down from prices of over $40,000 per watt to current retail prices of around $5 per watt, or in some cases as low as $3 per watt for distributors or in very large quantities.
How long do PV modules last? — Ken Harris, Salt Lake City, UT
PV modules last a long, long time. How long we honestly don’t yet know, as the oldest terrestrial modules are barely 45 years old and still going strong. In decades-long tests, the fully developed technology of single- and polycrystal modules has shown to degrade at fairly steady rates of 0.25%-0.5% per year. First-generation amorphous modules degraded faster, but there are so many new wrinkles and improvements in amorphous production that we can’t draw any blanket generalizations for this module type.
The best amorphous products now seem to closely match the degradation of single-crystal products, but there is little long-term data. Most full-size modules carry 25-year warranties, reflecting their manufacturers’ faith in the durability of these products.
PV technology is closely related to transistor technology. Based on our experience with transistors, which just fade away after 20 years of constant use, most manufacturers have been confidently predicting 20-year or longer life spans. However, keep in mind that PV modules are seeing only six to eight hours of active use per day, so we may find that life spans of 60-80 years are normal. Cells that were put into the truly nasty environment of space in the late 1960s are still functioning well. The bottom line? We’re going to measure the life expectancy of PV modules in decades - how many, we don’t yet know.
The best amorphous products now seem to closely match the degradation of single-crystal products, but there is little long-term data. Most full-size modules carry 25-year warranties, reflecting their manufacturers’ faith in the durability of these products.
PV technology is closely related to transistor technology. Based on our experience with transistors, which just fade away after 20 years of constant use, most manufacturers have been confidently predicting 20-year or longer life spans. However, keep in mind that PV modules are seeing only six to eight hours of active use per day, so we may find that life spans of 60-80 years are normal. Cells that were put into the truly nasty environment of space in the late 1960s are still functioning well. The bottom line? We’re going to measure the life expectancy of PV modules in decades - how many, we don’t yet know.
I've always heard that solar is more wasteful than efficient since it costs so much to produce the materials. Is that true? — George R.W., Los Angeles, CA
In the early years of the PV industry, there was
a nasty rumor circulating that said PV modules
would never produce as much power over
their lifetimes as it took to manufacture them.
During the early years of development, when
transistors were a novelty, and handmade PV
modules costing as much as $40,000 per watt
were being used exclusively for spacecraft, this
was true. The truth now is that PV modules pay
back their manufacturing energy investment
in about 1.5 years’ time (only a fraction of the
typical warranty period), depending on module
type, installation climate, and other conditions.
Now, in all honesty, this information comes to us
courtesy of the module manufacturers.
The National Renewable Energy Laboratory has done some impartial studies on payback time (see the results at www.nrel.gov/ncpv/pdfs/24596.pdf). It concludes that modules installed under average U.S. conditions reach energy payback in three to four years, depending on construction type. The aluminum frame all by itself can account for six months to one year of that time. Quicker energy paybacks, down to one to two years, are expected in the future, as more “solar grade” silicon feedstock becomes available, and simpler standardized mounting frames are developed.
The National Renewable Energy Laboratory has done some impartial studies on payback time (see the results at www.nrel.gov/ncpv/pdfs/24596.pdf). It concludes that modules installed under average U.S. conditions reach energy payback in three to four years, depending on construction type. The aluminum frame all by itself can account for six months to one year of that time. Quicker energy paybacks, down to one to two years, are expected in the future, as more “solar grade” silicon feedstock becomes available, and simpler standardized mounting frames are developed.
What is the maintenance on an installed solar power system? — Joanne Wyscomb, Boulder, CO
It’s almost laughable how easy the maintenance
is for PV modules. Because they have no moving
parts, they are virtually maintenance free.
Basically, you keep them clean. If it rains irregularly
or if the birds leave their calling cards, hose
the modules down. Do not hose them off when
they’re hot, since uneven thermal shock could
theoretically break the glass. Wash them in
the morning or evening. For PV maintenance,
that’s it.
What is an inverter? — C. Dalton, Buffalo, NY
An inverter is an electronic device that converts (transforms) the
low-voltage DC power we can store in batteries to conventional
120-volt AC power as needed by lights and appliances. This
makes it possible to utilize the lower-cost (and often higher quality)
mass-produced appliances made for the conventional
grid-supplied market. Inverters are available in a wide range
of wattage capabilities. We commonly deal with inverters that
have a capacity of anywhere between 150 and 6,000 watts.
What is a PV module? — G.K., Phoenix, AZ
This is what you might call a “solar panel” that makes electricity when exposed to direct sunlight. PV is shorthand for photovoltaic. We call these panels PV modules to differentiate them from solar
hot-water panels or collectors, which are a completely different
technology and are often what folks think of when we say
“solar panel.” PV modules do not make hot water.
I'm not sure if my house gets "full sun". What does that mean exactly? — Anne Hofstra, Bend, OR
Most people seldom see 100% full-Sun conditions. If you are not getting
full, bright, shadow-free sunlight, then your
PV output will be reduced. If you are not getting
bright enough sunlight to cast fairly sharpedged
shadows, then you do not have enough
sunlight to harvest much useful electricity.
Most of us actually receive 80%-85% of a “full
Sun” (defined as 1,000 watts per square meter)
on a clear sunny day. High altitudes and desert
locations will do better on sunlight availability.
On the high desert plateaus, 105%-110% of full
Sun is normal. They don’t call it the “sunbelt”
for nothing!
What is a 'utility intertie' system? It seems really complicated. — Frank West, Longview, TX
These are actually very easy. Whatever your renewable energy
system doesn’t cover, your existing utility company
will. So we don’t need to account for every
watt-hour beforehand. Tell us either how much
you want to spend, or how many kilowatt-hours
of utility power you’d like to displace on an average
day. For direct-intertie systems without
batteries, you’ll invest about $2,500 for every
kilowatt-hour per day your solar system delivers.
For battery-based systems that can provide
limited emergency back-up power, you invest
about $3,500-$4,500 for every kilowatt-hour per
day. These are very general ballpark figures for
initial system costs.
A lot of this stuff does seem complicated, but don't worry - that's what Real Goods is here for!
A lot of this stuff does seem complicated, but don't worry - that's what Real Goods is here for!
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