Enhancing Incentives
through Monitoring
Monitoring your PV system may have much
broader benefits than maximizing the power
output of your individual PV system. Monitor-
ing systems collectively across an entire state
or regional program can assist policymakers in
assessing how well these systems actually per-
form in different locations. These data are used
to answer a number of questions:
• Is the program meeting its objective of
using incentives to encourage optimal system
performance?
•;To;what;extent;are;solar;systems;connected
to the electrical grid contributing to peak load
and greenhouse gas reductions?
•;How;does;solar;system;performance;vary
geographically?
•;What;is;the;effect;of;solar;installations;on
the electrical grid?
Two large PV incentive programs in California collect data (including system performance
monitoring data) to answer the above questions:
the Self-Generation Incentive Program (SGIP)
and the California Solar Initiative (CSI).
The SGIP was established in 2001 as a
response to the peak demand challenges facing
California at that time. Under this program,
880 PV systems were installed from 2001 to
2006, totaling nearly 133 megawatts of aC
(M WaC) of generating capacity. During that
timeframe, PV system output information was
collected in 15-minute intervals, providing an
opportunity to evaluate the impacts of degradation, soiling and material type on PV system
output. The SGIP Eighth-year Impact Evaluation Final Report showed that the degradation
rate of flat-installation PV systems was greater
than the degradation rate of tilted PV systems.
That likely is due to a range of factors including weather, maintenance/reliability issues
and location. This information is valuable not
only to program administrators who design
the incentive programs to increase output
and system reliability, but also to individual
PV owners and manufacturers who want to
maximize the output of their PV systems over
the systems’ lives. (Itron Inc. “CPUC Self-Generation Incentive Program Eighth-year
Impacts Evaluation: Final Report.” Submitted to Pacific Gas and Electric Co. and the
Self-Generation Incentive Program Working
Group. June 2009).
Effective Jan. 1, 2007, incentive funding for
PV systems was moved to the CSI. Similar to
SGIP, the CSI provides incentives to reduce
the cost of systems installed in California. as of
mid-February 2010, nearly 27,000 systems total-
ing more than 300 MWaC of capacity had been
more data being tracked or more features offered
(such as storage), the more expensive the system
will be. The monitoring cost can vary from zero,
for inverter and web-based systems offered by
some larger installers or manually recording your
own inverter data, to $10,000-plus for the most
sophisticated systems. To determine what type
of monitoring system is best for your needs, you
will want to answer the following questions:
• What parameters are you interested in
monitoring? Typical parameters may include,
but are not limited to, power output, solar irra-
diance, ambient temperature, wind speed and
power consumption.
installed under this program.
The CSI offers two types of incentives: the
Performance-Based Incentive (PBI), which pays
per kilowatt-hour produced for the first five years,
and the Expected Performance-Based Buydown
Performance monitoring
for a large number of
systems allows regulators
and policymakers to structure
incentives and programs to
achieve the desired results
and performance.
(EPBB), which provides a one-time payment
after the system is installed. The amount of the
EPBB payment is based on what the system is
expected to produce. Monitoring is required for
the PBI since the incentive is directly linked to
actual system performance. For the EPBB incentive, with its lump-sum payment, system monitoring allows owners and policymakers to ensure
that appropriate incentives are being paid.
Figure 3 on page 50 compares how CSI systems that receive a PBI compare to those that
received a lump-sum payment (EPBB). This
graph is drawn only from 2008 data and may
be skewed downward due to the large number
of systems that came online in the latter part of
2008. although the data do not show statistical
differences (the confidence intervals overlap),
they do indicate that the average system receiving a PBI may outperform the average system
receiving an EPBB.
Performance monitoring for a large number
of systems allows regulators and policymakers to
structure incentives and programs to achieve the
desired results and performance. In the future,
one policy lever that may help ensure optimum
PV performance is tying incentives to actual PV
performance or requiring regular PV system
maintenance. Owners already have a financial
incentive to maintain their systems to optimize
energy, but enforcing that could help advance
PV market development. ST
