How much energy did your office use on Christmas Day?

28 Jan 2014 by Peter

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Offices Christmas

We often talk about the significant energy waste that occurs in commercial properties outside of working hours, and what a great opportunity it represents for improving energy efficiency.

This is largely based on some analysis we did last year which found that a typical commercial building sits empty around 72% of the year, yet uses 55% of its energy during this time.

The perfect example

As the ultimate example of this, we decided to look into office energy use on the day of the year that has the lowest building occupancy rate – December 25.

This involved digging into some data from our sustainability monitoring software to compare the energy use of six randomly selected commercial offices on Christmas Day 2013.

Analysing Christmas Day energy use

Christmas Day ‘13 fell on a Wednesday and so would normally have been a working day for most buildings.

To put each building’s Christmas Day energy use in context, we compared it to two other days in December – Wednesday the 11th and Saturday the 14th. These days were chosen to represent a typical working weekday, when the buildings were fully occupied, and a typical weekend day, when the buildings were empty.


The energy profiles for each of the six buildings over these three days are shown below. Our benchmark weekday is charted in grey, Christmas Day is in a festive red, and our benchmark weekend day is in green.

Christmas Energy chart

The results suggest that whilst we were enjoying a nice, relaxing Christmas Day, these buildings weren’t having such a good time.

Four out of the six buildings used significantly more energy on Christmas Day than on a typical weekend day; one building used about same; and one, Building E, used significantly less that usual (good job!). Across the group though, total energy consumption was 72% higher than our benchmark weekend day.

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So what’s going on here?

What often catches organisations out on public holidays such as Christmas Day or Australia Day is that the public holiday falls on what is normally a working day.

Whilst we’re well dialed in to the idea of a working week followed by a weekend – and so have timer clocks and building automation systems set up accordingly – public holidays often catch us out.

For example, it’s clear in Building F that the HVAC system fired up as usual on Christmas Day. If you look at the energy profile, you can see the tell tale spike of the HVAC as it kicks in around 7am. Notice the corresponding spike on the weekday benchmark data.

Perhaps people were really working?

Unlikely, right? But just to be sure, we surveyed 100 our clients just to check. Of the 36 people that responded, just one poor soul went into the office on Christmas Day.

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Wrap up

Powering down unoccupied buildings to the point that they use the bare minimum of energy and water sounds so obvious yet continues to give organisations a real headache.

Whilst most organisations will have some kind of process to shut their buildings down over weekends, public holidays often present a problem, simply because they don’t fall in a regular and consistent pattern. This means that public holiday dates are often not plugged into the building automation system and any manual processes often get overlooked.

So next public holiday, take the time to make sure your building takes a break too.

For more tips, check out our infographic, “15 Office Energy Saving Tips to Give Your Building a Holiday.”

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