ASHRAE Journal - June 2021 - 58

COLUMN RESIDENTIAL BUILDINGS
sensors and controls could be used
to improve efficiency, comfort and
enable more complex controls.13,14
For example, user-facing controls
could give occupants more insight
into how their water heater operates
and how to make changes to suit
their needs.
Electric Vehicles and Electric
Vehicle Charging
Electric vehicles (EV) are gaining
popularity rapidly and will have
profound impacts on the electric
grid. Currently, most EVs charge
when people come home, typically
coinciding with afternoon/evening
peak, further straining the grid.
Therefore, the ability for homeowners
or utilities to manage charging
for the growing number of EVs will
be critical for grid stability.
Increased EV adoption could benefit
the grid, as they represent a new
source of electric utility revenue.
Flexibility around charging could be
used for grid support.15 However, a
lack of communication between car
and home currently exists.16
The car monitors the state of charge
of the battery, calls for charging and
can regulate the charging power. But
in most cases, the car's battery management
system does not talk to the
electric vehicle supply equipment
(EVSE). Some EVs have mobile apps
that provide feedback on the battery's
state and can be used to set up
a charging schedule, but they usually
do not allow integration with a home
energy management system.
Multiple communication protocols
exist for vehicle/grid integration,
but car manufacturers, EVSE
manufacturers and utilities have not
settled on a common protocol for
managed charging.17
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Batteries
FIGURE 4 Residential battery and inverter.
Lithium-ion batteries are generally
limited to providing backup power,
but when paired with on-site solar,
batteries could help homeowners use
more local generation by storing the
energy until it is needed after the sun
goes down. That strategy only makes
financial sense if the home is on a
time-of-use utility rate or does not
get paid by the utility for PV generation
that is put back on the grid.18,19
Batteries can power a home during
grid outages but only if they
are installed with a grid-forming
inverter, critical loads panel and
transfer switch to keep the home isolated
from the grid during the outage.
Those additional components
make battery costs even higher.
Batteries and other energy storage
systems will be critical to achieve a
clean energy grid by 2035, but more
work is needed to encourage adoption.
As long as residential utility
rate structures remain flat, batteries
will likely remain a niche backup
power option. With dynamic or
time-varying utility rates, batteries
can play a key role in reducing costs
for homeowners and helping utilities
shift load to times with available
renewable energy.19
Power Measurement and Management
Even as more equipment in homes
becomes smart, we will not truly
have smart homes unless there is a
way to measure and coordinate the
control of the various smart appliances.
This area of smart home technology
development is the furthest
from becoming mainstream, but
companies and research organizations
are working to bring wholehome
monitoring and control to
maturity.
J U N E 2021
Whole-Home Power Metering
Monthly utility bills are the only
feedback most people receive about
their energy use. More frequent
feedback is needed to improve home
energy management. Smart meters
can provide more frequent use data,
but even that is generally not granular
enough for consumers to use.
Some new products can measure
whole-house power consumption at
high frequencies and can use that
data to identify power consumption
of specific appliances.20
These systems can provide feedback
to help homeowners take
action to reduce energy use based on
their use patterns.
Smart Utility Panels
Emerging new smart utility panel
technologies and other advanced
power management devices can provide
more control, as well as circuitlevel
monitoring.21 These will enable
more integration of advanced systems
like batteries and on-site solar
panels. Some advanced smart utility
panels make it easier to use batteries
for backup power by including an
integrated transfer switch and giving
users the ability to select their critical
loads during an outage, rather than
having a separate critical load panel
that cannot be easily changed.
Circuit-level monitoring and
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ASHRAE Journal - June 2021

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