Can you tell us about the different ways that Zero Net
Energy is defined?
KP: It is first important to point out that buildings are
planned and built to serve some function or mission and
we should never lose sight of this. For example in schools,
the primary function is to educate students and the
building indoor environment should provide an optimum
atmosphere to further this mission.
There are multiple definitions for Zero Net Energy. In the
U.S., it means that the energy that’s consumed in the
building is offset by renewable energy on an annual
basis, either onsite or sometimes offsite. Energy use is
measured on an annual basis, as solar renewable energy
production increases in the summer months. And a Net
Zero building really means net positive, as these buildings
are typically going to produce slightly more renewable
energy than they use.
Additionally, you can look at Zero Net Energy from the
individual building level, a multi-building campus, or a
portfolio of different building sites owned by a single
entity. There’s even a definition for Zero Net Energy
Communities. These different definition variations are
flexible enough to recognize that not all buildings are
created equal.
How do you achieve Zero Net Energy in a building?
KP: The first step is to have a very energy efficient
building. Today, that would be anywhere from 30-50%
less than the California Energy Code. When you design
a Zero Net Energy building, you model how much energy
the building’s really going to consume based on hours of
occupancy and occupant loading and then you offset
that annual energy with renewable energy. More so
than for other buildings, operators, occupants, and plug
loads will play a very important role to get the building to
function as designed.
This is also where commissioning services become critical
to make sure the systems are installed and perform as
required. Commissioning also oversees all the training for
the building operators.
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What do you think is more important for wider Zero Net
Energy adoption? Appropriate regulations or buy-in
from building owners and developers?
KP: The easiest way to adopt something new is to
make the business case for it. If it makes sense from
a life-cycle-cost perspective, then it could easily be
adopted. Policy by itself usually doesn’t do a good job
of increasing adoption. I’ll give an example. We’ve had
the California Title 24 Energy Code in effect since 1975.
I still see today, many of the Title 24 provisions not
implemented by design professionals or enforced by
code officials. If it makes sense to business owners and
they believe it will help with their mission, then they are
more likely to adopt.
Will ZNEs ever be cost-effective enough to gain
widespread market adoption without incentives or
subsidies?
KP: Yes, there have been changes within the last five
years that would probably make ZNE make more sense
for many business and home owners, depending on their
building location. Residential PV (photovoltaic system)
has gone from $7.24/watt in 2010 to $2.80/watt in 2017.
Commercial PV has gone from $5.36 per watt to $1.85
per watt. Utility-scale PV cost $1.03 in 2017, now it’s at 55
cents per watt. It’s halved within a year, it’s unbelievable
what the cost of PV has come down to.
In California, we have clients installing PV with a Power
Purchase Agreement (PPA) and the cost/kWh of the PPA
are less than what the public utilities are charging for
electricity. Today, there are many examples of ultra-
efficient buildings for little to no additional premium of
what was budgeted for a building that met the energy
code. All it takes is a good integrated design team
that can look at architectural features, orientation,
operations and can design the right mechanical and
electrical systems in the building to get annual energy
consumption as low as possible. Owners can then decide
if they want to carry the capital cost of the PV systems or
use a PPA as a funding mechanism. Because of this, ZNE
is becoming much more attractive to building owners.