Comly Wilson, Associate with CleanEdison, a solar installation training provider, offers her tips to remedy 6 common mistakes solar PV installers make when setting up new photovoltaic systems.
Okay, so you’ve got some equipment, you’ve got some know-how
and you are ready to get out there and become a solar installer. Sounds
easy enough, I mean everyone is talking about it, right? Well yes, but before
you start going onto people’s roofs and drawing high-voltage DC electricity
from the sun, you should know the common mistakes that others (many others)
have made before you. This is by no means a list of all the questions you will
have, or problems you will run into, but it should help dispel some
misconceptions you may have about solar energy.
I learned that solar PV panels lose their efficiency as they
get hotter, but I also know that solar thermal collectors use water heated by
the sun for use in the home. I could just use the water to cool the PV panels
and then it would be heated for hot water use. I’m a genius!
I don’t blame anyone for thinking this. I know I did at
first, as I’m sure 90 percent of people learning about solar energy
have. The truth is that the math doesn’t work out. In order for
your hot water to be sufficient for uses such a showering and washing dishes, it
should be in the tank at 120 degrees Fahrenheit, which means it would have to
be 130 degrees on the roof and the solar panels would have to be 140 -150
degrees. This is a far cry from the optimal temperature of most solar PV brands
at 77 degrees. So, either you’ll be showering in cold water or you’ll be
waiting an awfully long time to get a return on those inefficient solar panels
(which you’ll need to combat the 140 degree temperature outside).
I’m just going to install a small stand alone system to
power one or two things, like the air conditioning and refrigerator.
AC and refrigeration are the two biggest energy users in a
home. A small system not tied to the grid would have a lot of trouble running
the AC and refrigerator consistently. If you’re going to install a small
standalone system, connect it to smaller end uses, such as the computer, TV, or
lighting fixtures. There is nothing wrong with a small system, but having it
grid-tied can help tackle those big energy users while keeping the consistency
It seems like the competition is over-charging for
installations. I just checked the prices of solar panels and they’re dropping
The truth is that while the costs of panels themselves have
dropped tremendously in recent years, the installation costs have only dropped
slightly. There are plenty of other materials that go into a solar installation
that you will need (and be expected to supply). The racking, DC disconnects,
heavy gauge wiring and other BOS (balance of system) hardware can add up to
more than the panels themselves – making the real installation costs close to
where you notice the competition (and don’t forget about your labor). These are
simply expenses that you cannot overlook, solar PV systems are dangerous and
the safety for yourself and the homeowners could be compromised if you buy
cheap or faulty auxiliary components.
Wait, what!? How is a 3 kw system supposed to make a dent in
a house that uses 600 kw each month?
Kilowatts are a measure of instantaneous electricity
generation (e.g. right now your system is producing 3 kw), while kilowatt-hours
are a measure of cumulative electricity usage/generation over time (e.g. your
system produced 8 kwh of solar power today, and your home used 16 kwh of power
to run its appliances). When referring to solar PV system capacity, the term
kilowatt is usually used – this indicates the ‘peak’ capacity of the panels or
system. Real life production will likely be lower, depending on conditions.
Getting grid tie approval sounds impossible. I’m just going
to add more batteries to my system and switch back to the grid only when these
The approval process for grid tied systems can be quite
difficult (although the DOE is making it a lower priority), but the opportunity
cost of purchasing batteries will be clear once you realize the upfront cost
and lack of longevity. Most batteries only last a year and a half if they are
routinely discharged to 50% or below. On the other hand, batteries that are
connected to a hybrid inverter that keeps them float charged all the time while
feeding excess power back to the grid can last upwards of 20 years.
It’s sunny from 8 a.m. to 6 p.m. here, so my I can expect
the panels to run at full power for about 10 hours a day.
Most systems really see full power for only a few hours a
day. The rest of the time the sun is at an angle, preventing the panels from getting
the full power. Thus 10 hours of daylight might give you only 4 hours of
equivalent direct sun – and direct sun is what you have to base your total
energy output on.
Hopefully this will help future installers avoid the
mistakes and misconceptions of many before them. Of course, with the proper solar
training these mistakes can be remedied before you leave the classroom. In any
case, it is a good idea to go out with an experienced installer for the first
several installations to really cement your knowledge and skills.
CleanEdison is a national training provider offering online,
in-classroom, and hands-on vocational training to professionals, businesses,
postsecondary institutions, government organizations and novices.