August 2024 Green Power Page 3
meters. The green arrows correspond to information about your onsite system (your onsite renewable
meter); the black arrow corresponds to information about energy from the grid (your grid electric meter).
1. Onsite Solar or Wind Meter (Labeled as Flow R). This meter is used to track both the
electricity that you use onsite and any electricity that is exported back to the grid.
•
Electricity generated by your system and used at your building (Labeled as Flow
R
u
). The energy you generate and use onsite is an important energy need that must be
included in your energy performance metrics. This amount is not always metered, but
most buildings do meter the total amount of electricity generated, and if you do not export
any energy to the grid, then this is the amount you need. If you do export electricity to the
grid, and you do not have a physical meter tracking the amount of electricity you use you
will need to compute this value by measuring your total system generation (R) and
subtracting any exports to the grid (R
ex
). You may want to consult with the energy service
provider or utility that assisted with your system installation to determine where you can
find this amount (energy that is generated by your system and used at your property).
•
Electricity generated by your system and exported to the electric grid (Flow R
ex
).
Many onsite systems export electricity to the grid. For example, a small school may have
periods during which the generation of the onsite system exceeds the building’s demand
and therefore the excess electricity is exported to the grid. In contrast a large office
building may never generate more electricity than it needs and therefore will not export
any electricity. If you export electricity, you must quantify your exports. This information
might be obtained from a bi-directional digital electric utility meter installed at your
property that measures flow to the grid. Some buildings may not be able to read this value
from a physical meter on their site, but rather will find it on the utility bill. You may want to
consult with the energy service provider or utility that assisted with your system
installation to determine where you can find this export amount.
2. Grid Electricity Meter (Flow G). This Portfolio Manager meter is used to track all electricity that
is sourced from the grid, meaning all electricity (kWh) that flows from the grid to your building. If
you do not export green power, then your utility bill is your total grid electricity. If you do export
green power, then you need to be very careful to include
all
energy that flows from the grid to
your property; this is typically tracked via a bi-directional meter and may be reported on your
utility bill. It is not sufficient to enter a “net” meter, which only shows you the difference between
the energy you import from the grid and the energy you export (i.e., G – R
ex
). Although your utility
may give you financial credit for exports (R
ex
), the total flow of energy from the grid into your
building (G) is required for a complete assessment of your performance. It is common for utility
bills to separately report the “net” value (G – R
ex
) and the export value (R
ex
). In this situation, you
will need to compute G by adding these two values together. You may want to consult with your
energy service provider or utility to determine how you can quantify G from your utility bill.