Building controls companies have poured tremendous technical effort into algorithms for optimizing start times in commercial buildings. Despite their promise, these systems so far appear to have little traction — across our customer base, less than 5% of buildings vary their start time by season. That’s a big opportunity: 25% of buildings are currently starting before 4am. In California, every extra 100 kWh of morning electricity use costs $1,500 per year.
There is a simpler way. We call it the “yelp” method, and we’ve been helping facility teams implement it for easy savings.
First, imagine you have a suspicion that you can start your building later. A quick peek at your Snapmeter report tells you what time most systems are turned on. The example below shows a 4:45am start:
Second, consider whether you can advance the start time. As we head into spring, morning chill is losing its bit. Lease hours don’t begin till 8am, and the parking lot is not really crowded until 9am. You suspect you can postpone startup at least two hours (and pocket $3,000 in annual savings).
Here the magic starts. Roll forward your start time, 15 minutes at a time each day. Carefully track hot and cold calls. When you hear the “yelp” from occupants, simply rewind to the latest startup time that doesn’t cause any complaints. Congratulations, you’ve found a way to keep tenants satisfied while minimizing energy use.
Typically you can execute the changes each day, but pay attention to tough days or extreme weather. Mondays in particular can be a challenge due to weekend heat loss. You may want to experiment with Monday startup times separately. This method works in all buildings, even those without a BMS. If you have 36 air handlers, one on each floor, just pick a handful of floors that you feel are representative, run the experiments, and then replicate across the other floors.
You’ll want to repeat the experiment in different seasons and again use complaints to dictate tiny changes along the way. Imagine that you find that the first complaints come at a 6:30 start time, so you settle on 6:15 for a few months. As you get deeper into the summer, respond to any heat complaints by slowly rolling back the start time, 15 minutes a day, until the complaints stop.
The yelp method does give a lot of power to the most vocal occupants in your building. Sophisticated control algorithms in your BMS like critical zone reset and static pressure reset typically ignore feedback from one or two devices to make sure they are not unduly influenced. You may want to do the same in your building. (Pro tip for occupants: you should always be gracious and kind to your chief engineer.)
This method isn’t especially elegant, and it’s certainly not automatic. It ignores variation in morning temperature by month. But it will put money in your pocket tomorrow. Just roll forward that start time and listen for the yelp.
