This document discusses how reducing energy use in buildings during the 72% of time they are typically unoccupied can be one of the easiest and most impactful ways to improve energy efficiency. It notes that on average, 55% of total electricity usage in commercial buildings occurs when they are empty. The document examines the costs of this wasted energy use and identifies common energy vampires like electronics and appliances that are left on. It provides recommendations for analyzing usage data, engaging occupants, and implementing simple solutions to curb out-of-hours consumption.

1. out of hours
The easiest way to improve your
building’s energy efficiency
TOWN HALL

2. About your authors
Here at Greensense, we provide award-winning sustainability monitoring
software for buildings, campuses and communities. Our flagship product,
Greensense View® helps to:
Reduce energy, water & waste
Engage Occupants
Use real-time monitoring of
resource consumption to identify
operational issues and savings
opportunities.
Engage staff, students or
communities in your sustainability
programs.
Showcase Green Initiatives
Streamline Reporting
See the ROI of green investments,
effectively tell your sustainability
story and earn Green Star points.
Quickly and easily arm yourself
with the data you need to support
reporting regimes such as
NABERS and NGERS.
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3. contents
1. Intro
2. Don’t guess. Know.
3. The easiest way to improve building energy efficiency
4. Calculating the cost
5. The culprits
6. Getting started
7. Challenges
8. Wrap up

4. 1. intro
Buildings are our biggest energy consumer
Why is this ebook focused on the energy efficiency of buildings?
Surely there are bigger fish to fry?
Actually buildings are our biggest energy consumers – research by the
U.S Department of Energy, and results are similar in Australia, found that
“buildings consume more energy than the transportation or industrial
sectors, accounting for nearly 40% of total energy use.”1
So, with that in mind, there are few better places to start when looking to
improve environmental performance.

5. 2. Don’t guess. know
Let data be your guide
One of the biggest challenges of any building energy efficiency program
can be deciding where to start. This can be tough if you’re talking about one
property, and particularly tricky for managers of large portfolios.
To set off on the right track, data can be your biggest friend. If analysed and
presented correctly, it can be hugely powerful, both in terms of identifying
where to begin on your energy efficiency quest, as well as providing the
means to track and quantify performance improvements over time.
To save you spending days wading through reports and spreadsheets, we
did some analysis using data from thousands of buildings. The results were
fascinating and pointed to one rather obvious, but compelling, way to
improve building energy efficiency.

6. 3.The easiest way to improve building
energy efficiency
Based on buildings across a range of sectors and industries – including
offices, education and government – we found that buildings are on average
empty for around 72% of the year.2 Makes sense right? What with most
people clocking off in the evenings, weekends and holidays.
55%
From a sustainability perspective, there’s nothing wrong with having an
empty building, so long as it’s not consuming energy while sitting idle.
Unfortunately, that is never the case, far from it in fact.
Our analysis found that typically 55% of all electricity use occurs during this
time. That’s more than half an organisation’s energy consumption being
pumped into an empty building.
45%
Commercial and government buildings are
typically empty around 72% of the year and
use a whopping 55% of their energy during
this time.
Source: Greensense View®
Why is this? The numbers showed that most buildings have relatively
high levels of ‘base load’, meaning they continue to consume significant
amounts of power even when they’re empty. This becomes a very important
consideration when you’re looking at improving efficiency. To help remedy
this, let’s look at the costs, culprits and a few solutions.

7. $$$
4. calculating the cost
As always in discussions around building (in)efficiency, when it comes
to costs we need to consider both the environmental and the financial
implications.
The environmental cost is pretty easy to work out. In Australia, each
kilowatt-hour of electricity poured into an empty building generates around
0.9kg3 of greenhouse gas emissions. Of course, you might be subsidising
your wasted electricity through some onsite renewables, such as solar, but
remember that the majority of this out of hours consumption is going to
occur at night when your PV can’t help.
The financial cost is trickier to calculate as it will depend on the tariff for
each building. In order to explore the cost question a little further, and at
the same time to illustrate the value in understanding your building’s energy
profile, the graphic on the following page illustrates how significant out of
hours consumption can be to the financial bottom line.
It compares the average weekly energy consumption for three office
buildings. The buildings are located within a few kilometres of each other in
a major Australian city, are of very similar size, have very similar operating
hours and perform the same function. In many ways they are typical
examples of office buildings.

8. Energy used after hours:
38%
After hours cost:
Office A
Council A
$109,000 per year
Energy used after hours:
55%
After hours cost:
Office B
Council B
$131,000 per year
Energy used after hours:
63%
After hours cost:
Office C
Council C
$182,000 per year
Mon
Tue
In hours
Wed
Thu
After hours (peak)
Fri
Sat
Sun
After hours (off peak)
Despite the similarities in form and function, the amount of energy going
into these buildings during out of hours periods varies hugely, with
correspondingly significant implications in terms of operating costs. Even
the ‘best’ performer here is spending over $100,000 a year powering an
empty building!
What the graphic also shows is that, while benchmarking can put the out
of hours performance of each building in context, taking a seven day view
of resource consumption is extremely useful in understanding when that
energy is being used.
Note: Cost estimates and peak / off
peak periods are based on Synergy’s
R3 Time of Use Tariff as of June 2012
Source: Greensense View®

9. 5. the culprits
Exactly where all that out of hours electricity is going will vary from
building to building but, even without sub-metering data, we can make
some informed guesses.
In a typical office building there are three main energy users: HVAC (50%),
lighting (25%) and plug loads (25%).4 HVAC is often centralised in larger
offices, although you might still have a few split-system units around the
place, and lighting control is increasingly centralised too. So, while they may
be playing a part in the story, it will most likely be plug loads that are the real
culprit and must inevitably form the focus of any out of hours performance
improvements.

10. Power to the People
Perhaps the most interesting element here is that plug loads are the chunk
of electricity consumption over which building occupants have the most
control. Plug loads are not typically managed by the building; rather, they are
managed by you and I. Even allowing for the rollout of power management
software and hardware for PCs, there is still a significant proportion of
energy use over which occupants have almost total control.
For the most part, as building users we give little thought to how our daily
choices impact energy efficiency; yet we’ve seen time and time again that,
by increasing occupants’ awareness and providing feedback in a relevant,
actionable way, it’s possible to realise significant savings. Some big brains
at Oxford University have backed this up with research that showed that
providing direct feedback on energy consumption to users can generate 1015% savings.5
Within workplaces this can be particularly effective when supported by
behavioural change initiatives such as energy reduction competitions
and challenges.

11. 6. Getting started
A bit of data digging will help identify the biggest contributors to your
building’s out of hours energy use. Some questions to kick things off could
be:
1. hat’s our biggest out of hours opportunity?
W
Is our main energy user plug loads, lighting, HVAC or maybe the server room?
2. If plug loads (most likely), what are the biggest offenders?
3. re there any devices that are left on but not used at night? Can we upgrade,
A
use a power saving mode or simply turn them off?
4. rmed with this information, which building occupants and champions should
A
we engage to see the biggest results?
5. hat data will people need to be aware of and how can we provide it in an
W
engaging way?
6. hat other relevant information can we provide to educate and motivate
W
people? Remember to always frame any data you’re sharing in a way that your
staff can easily understand and relate to.
7. ow else can we encourage behaviour change? e.g. an energy saving
H
competition or a tie-in with an event such as Earth Hour or the Global Corporate
Challenge.
All these suggestions are straightforward enough and, best of all, shouldn’t
cost much if anything to implement.

12. 7. challenges
55%
“We’re pumping 55% of our energy
into empty buildings. Who thinks
we should do something about it?”
Selling internally
It’s important to be pragmatic when looking to roll out environmental
programs and energy efficiency is no different. There will likely be a number
of (often competing) project options, whether it’s covering the building in
solar panels or turning up the set point on the A/C. While many of these
projects will have merit, a number will present significant obstacles such
as upfront cost (solar panels) or push back from building occupants (A/C
tweaks).
By starting your energy saving quest by focusing on out of hours use, you
remove most of these barriers. First and foremost, nobody can deny that
pouring energy into an empty building is wasteful. Secondly, the steps taken
to reduce this waste are often relatively uncomplicated. Why? Because the
building is empty for a start. It’s much easier to affect change in an empty
building, as you don’t have to worry about upsetting the occupants.
Coupled with that, the savings you’ll find are often from simple, operational
tweaks such as shutting down printers and PCs at night.
Accessing data
The most immediate challenge for building owners and tenants wanting
to explore where their energy is going will be gaining access to data. The
nature of this challenge can be both technical – do we have sufficient
metering to tell us what we need to know – as well as political – are we
allowed access to metering data for our tenancy. This can be particularly

13. troublesome for tenants in large commercial buildings where data on their
energy consumption is often carefully guarded by the building manager.
Thankfully, with an ever increasing focus on efficiency, sub metering is
becoming much more common, and the attitudes of building managers
are softening a little, although there is still much work to be done and we
encourage you to proactively engage your building manager around data
access.
Engaging people
Depending on your organisation’s culture, engaging people in your energy
efficiency programs may be straightforward and fun, or an uphill struggle.
Either way, success will largely depend on how the program is marketed. Is it
packaged and communicated in a fun, engaging way? Are key stakeholders
on board? Are there champions maintaining momentum? Do your staff feel
empowered and involved in the process? Tackling questions such as these
will go a long way to accomplishing your goals.
Energy
Competition

14. 8. wrap up
For those aspiring to improve the energy efficiency of their buildings, getting
to grips with out of hours consumption is an obvious, and often rewarding,
place to start.
By focusing on one particular element of building performance, it helps bring
direction and clarity to your efficiency program. All you need to get going is
some decent quality interval data and the ability to analyse it in a way that
helps you determine how much of your precious and increasingly expensive
energy is going into empty buildings. The results will be startling and should
provide all the incentive you need to start tracking down those savings.

15. references
1
U
S Department of Energy, ‘Energy Efficiency Trends in Residential and
Commercial Buildings’.
2
A
365 day year is composed of 8760 hours. Of those 365 days, only around
250, or 2500 hours (assuming a 10 hour operating day), are working days.
The rest are weekends and public holiday. This means that the majority of
commercial buildings are actually only operating for about 28% of the year.
For the other 72% of the time they’re sat empty.
Based on the 2012 NGA factors http:/
/www.climatechange.gov.au/~/
media/publications/nga/NGA-Factors-20120829-PDF.pdf
3
4
2006 review of LEED-NC v2 energy modelling
5
E
nvironment Change Institute, Oxford University, ‘The Effectiveness of
Feedback on Energy Consumption’.

16. Improve energy efficiency with Greensense View®
Reducing out of hours energy use is just one way to improve building
sustainability. By monitoring resource consumption in real time,
Greensense View can help you uncover many more.
Drop us a line to see a demo.
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