By Jason Roeder
Director of Energy Products and Services, Powerhouse Dynamics, Inc.
With the first day of summer officially in the books, the cooling season is on for the lower 48. Yes, Florida and Arizona and San Diego have been cranking air conditioning for weeks if not months by now, but the real heart of the cooling degree chart is now just in front of us. In fact, the average number for cooling degree days across the lower 48 is just about 1500 cooling degree days (look your city up here). For most small commercial businesses with 3-4 roof top units, the cost for comfort cooling will come out to be roughly $10 per cooling degree day. Fifteen thousand dollars for comfort cooling doesn’t sound too bad, but wouldn’t you rather pay less than that? After all, if you are a restaurant, that $15,000 may be 25% of the profit you earn for the entire summer.
Rooftop unit (RTU) based comfort cooling is rife with inefficiency. Turns out RTUs are fairly sensitive machines that live in a harsh environment that is out of sight and out of mind for many managers or property owners. Failure to monitor your RTU’s may lead to inflated summer cooling costs of 25%-75%.
But I digress. Take heart good reader, there is hope. Here are a few practical tips to cut those inflated cooling costs by 35% or more.
Smart Move #1: Maximize the value of your programmable thermostat.
This may generate a few eye rolls, but the studies all say that the majority of thermostat users do not program their thermostats to use their full capability. Until recently, thermostat interfaces have continued to be tough to use, but that is changing fast. In my humble opinion, there is now no reasonable excuse for not thinking carefully about your set points and time of day periods and translating that thought into the program in your thermostat, be it an internet thermostat or a traditional wall fly.
The tougher question is what to program? For starters, know when your cooling needs peak and trough. In the case of a restaurant, aim to hit your initial set point 1 hour before the lunch rush and at least 1 hour before closing plan to coast to the next set point. It may seem like overkill to use all 8 time periods during the day, but keep in mind cooling season is a battle of BTUs – every one counts. Even 24/7 operators can still do micro adjustments throughout day to save 1-2 hours of cooling time a day.
Also, remember that the temperature is for the guests, not the staff. To that point, staff control of the thermostats is not a best practice. To help head off this potential conflict, train the entire team so that everyone is aware and feels involved. And, don’t be afraid to get a little Jimmy Carter on your team if need be. Let’s all recall that EPA studies show every degree adds 2-3% to your cooling costs, so a set point of 70 vs 72 is 5%, or $250 – $1000 for the summer. A thousand bucks at $20 a cover is 50 new customers, so if a vocal employee thinks it’s too hot for them to work, tell them to hit the pavement and find another 50 customers to make up the difference.
Also, schedule thermostat checks once a month to verify that what you want to happen is happening. If you are feeling challenged, get one of the many internet thermostats on the market and do the “programming” on your PC or mobile device – no more strange menus and pushing arrows for minutes at a time.
Smart Move #2: Reduce Excess Cooling Loads
Why do we need mechanical cooling at all? Answers an engineer would provide include “solar gain” or “occupant cooling load”, or “lighting”, among others. For restaurants or convenience stores or even retail, much of the answer is indeed people and indoor machines that generate heat. That heat needs to be offset with cooling otherwise the space temperature will rise. When it comes to restaurants, there are many such machines.
One of the largest sources is exhaust hoods that sit over grills and stoves. These units do us a service by removing hot air and grease and such, but they can also do a large disservice by removing expensive, air conditioned air. A hood like the one pictured here can suck out your entire restaurant’s worth of air…every hour. In fact, this type of ventilation can represent 20%-40% of your entire cooling load. To help avoid sending too many cooling dollars up the hood, try to adjust of the start-up time for the hood from say 530AM to 830AM. This simple change can make a meaningful impact on your cooling load, and can easily be made.
Another equipment type to consider is heat generating equipment like heat lamps. A human at rest will add 450 Btu/hr of heat to a dining room. If you are using a 1,000 W heat lamp for cooking or warming, you are adding 3,400 BTUs/hr. So the question is: how many extra guests do you have standing in your kitchen? When possible, consider powering down your heat lamps during the lull between lunch and dinner or experiment with not using them at all for lunch. One ton of cooling is 12,000 BTUs, so it doesn’t take many heat lamps or ovens to soak up one of your 3 RTUs entirely.
Cooling costs can be contained with smart moves like these. Check out two more smart moves in this on-demand webinar.