Solar energy vs. shade - Solar, Wind and Land: Conflicts in Renewable Energy Development - page 98

nemesis of solar PV systems, rendering them far less productive than when
they have direct exposure to sunlight. Even relatively minor shading can
have major impacts on a solar array's electricity production. According
to one study, shading just 10 percent of some solar panels can cause a 50
percent reduction in their electricity output. 2
Although landowners can prevent trees or buildings on their own parcels
from shading their solar energy systems, they often have far less control
over trees or construction on neighbors' land. This risk of unwelcome
shading from a neighbor's tree or new building can unnecessarily deter solar
panel installations in jurisdictions without policies to adequately govern
solar access conflicts.
What is the solar access problem?
A simple example is helpful in illustrating how solar access conflicts can
arise. Suppose that a landowner who is interested in solar energy (Solar
User) plans to install an array of PV solar panels on the rooftop of her
home. Although prices for PV panels have fallen dramatically in the past
decade, solar arrays are still quite expensive. Accordingly, based on some
preliminary research, Solar User predicts that it will take roughly 15-20
years for her to recoup the cost of the array through savings on her
electricity bill. Solar User is more than willing to make that investment, so
she purchases and installs the system.
Unfortunately, a couple of years after Solar User installs her rooftop solar
array, she notices that a tree on her neighbor's property is beginning to
shade the panels in the winter months during certain hours of the day. The
neighbor's tree continues to grow and to shade an ever larger proportion
of the solar array and for longer periods throughout the year, as shown in
Figure 5.1 below. Not surprisingly, Solar User is beginning to notice reduc-
tions in the quantity of electric power her solar panels are generating and
is seeing a consequent rise in her monthly electricity bills. When Solar User
asks her neighbor to trim the tree to reduce its impact on her solar array,
the neighbor refuses. Solar User feels helpless, seemingly unable to avoid the
economic losses resulting from the shade from her neighbor's tree.
This risk—that a neighbor could grow a tree or erect a new building that
casts unwanted shade across the property line—is a factor that landowners
must consider when contemplating whether to get a rooftop solar energy
system. In some cases, parties in Solar User's position can convince
neighbors to voluntarily sell solar access easements or covenants to protect
against this risk. In fact, laws in many U.S. states specifically provide for the
enforceability of solar access easements. 3 These easements prohibit servient
landowners from occupying those portions of the airspace above their land
with trees or structures that would shade the dominant owner's solar array.
Unfortunately, some landowners are unwilling to grant these easements,
even for a reasonable price. When a neighbor refuses to grant a solar access