Some renewable energy enthusiasts obsess over solar panel efficiency, believing that it’s
the only important factor in producing photovoltaic energy. This isn’t surprising, as panel
manufacturers are constantly claiming to have beaten the world record for solar cell
Yes, solar panel efficiency is important, but it isn’t critical.
Putting Solar Panel Efficiency into Perspective
According to EnergySage, an online solar information marketplace backed by the U.S.
Department of Energy (DOE), the average solar panel efficiency rating ranges between
14 and 16 percent.
That may sound low to you, but to put things into perspective, consider your car. The
DOE says that conventional vehicles aren’t much more efficient than the average solar
panel. Only 14 to 30 percent of the energy generated by a gas engine goes toward
moving the car. The rest is mostly lost to inefficiencies in the engine and driveline.
What if you drive a hybrid vehicle? You’ll get about 25 to 40 percent efficiency. And with
electric cars, anywhere from 74 to 94 percent of energy is used to power the vehicle’s
movement. But don’t forget that both hybrid and electric vehicles must be charged with
electricity, which reduces their overall efficiency rating.
Doing the Math on Solar Panels and Efficiency
You aren’t likely to stop driving because you’re waiting for car manufacturers to design a
vehicle with better energy efficiency ratings. Neither do you need to wait for photovoltaic
panels to become more efficient before installing a home solar array.
If you aren’t convinced, let’s do some math.
The average home in the United States receives about 5 hours of sunlight per day,
which exposes a photovoltaic array to 5 kilowatt hours (kWh) of solar energy. This
means that each square meter of a photovoltaic panel with a rating of 15 percent
efficiency will capture 0.75 kWh of energy each day:
5 kWh × 0.15 efficiency = 0.75 kWh
The average household uses about 30 kWh of electricity each day. Generating this
would require 40 square meters of solar panels:
30 kWh total ÷ 0.75 kWh per square meter = 40 square meters
This works out to just over 430 square feet of roof space required for the photovoltaic
array. So how does that translate to your home’s rooftop?
How Much Space Does Your Rooftop Have for Solar Panels?
A two-story, 2,300-square-foot home that has a medium-pitched roof has a total roof
area of around 1,500 square feet. Of course, not all of that space is usable for mounting
a solar array, but much of the area can probably hold photovoltaic panels.
According to our math, the average homeowner only needs 430 square feet to
effectively power their home for a photovoltaic array — that’s less than one-fourth of the
average two-story rooftop.
As you can see, space probably isn’t an issue. This means that solar panel efficiency
doesn’t really matter so much, because most homeowners could use less efficient
panels and still have enough rooftop space.
The experts at Intermountain Wind & Solar, serving the states of the Intermountain
West, can answer all your questions about solar panel efficiency and explain other
important design considerations for a home photovoltaic array. Give us a call or visit our
website today to learn how you can slash your power bills and establish your energy
independence with rooftop solar panels.