One of the biggest challenges of any building energy efficiency program can be deciding where to start. This can be tough if you have one property, and particularly tricky for managers of large portfolios.
Data is your friend
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 recently did some analysis using data from thousands of buildings. The results were fascinating and pointed to one rather obvious, but compelling, place to start your energy efficiency program.
After hours energy use
Based on buildings across a range sectors and industries – including offices, education and government – we found that buildings are on average empty for around 72% of the year. Makes sense right? What with most people clocking off in the evenings, weekends and holidays, a building is empty far more often than occupied.
From a sustainability perspective, there’s nothing wrong with having an empty building, so long as it’s not consuming any 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 a year’s energy consumption being pumped into an empty building.
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 you’re looking at improving efficiency. To help remedy this, let’s look at the costs, culprits and a few solutions.
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 0.9kg** 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, however as an example, we compared the out-of-hours energy use and associated cost for three similar office buildings, situation within a few kilometres of one another in a major city.
Despite the similarities, the amount of energy going into these buildings during out-of-hours periods varied hugely, with correspondingly significant implications in terms of operating costs.
Office A used 38% of its annual energy after hours at a cost of $109,000 per annum. Office B used 55% of its energy after hours at a cost of $131,000 and Office C used 63% of its energy after hours at a cost of $182,000.
So even the ‘best’ performer in our sample was spending more than $100,000 a year powering an empty building!
So where is all that energy going?
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%)***. 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.
An easy starting point
Sometimes 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.
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.