I have often been struck by the wide range in claims about the effectiveness of an Energy Management System (EMS) in reducing energy usage. I have seen claims of anywhere from 10% to 35% in expected savings. While this wide range may be attributable to the range in functionality of different systems, I have actually seen this full range claimed even for systems that have the same functionality of heating and cooling control only.
I thought it would be interesting to explore what levels are reasonably achievable, to help in the process of parsing claims made by EMS vendors. Since we focus on smaller commercial facilities, let’s limit the discussion to facilities under 15,000 square feet and look at both retailers and restaurants in particular.
EMS Savings in a Retail Environment
Energy usage varies based on a wide variety of factors, perhaps the most important of which is climate. To keep things simple, however, it is not unreasonable to assume that in a “typical“ retail environment, heating and cooling is responsible for 40% of the load, lighting represents an additional 40%, and the remaining 20% is for water heating, plug loads, and other miscellaneous uses.
Let’s further assume that our retail location is open 12 hours per day. According to studies, for every 1 degree adjustment in cooling set point you save about 3% (again a simplification; the range varies based on a variety of factors). If the cooling set point overnight is moved from 72 to 80 degrees, the overnight savings will be about 24% for that period, which puts the total HVAC savings at 12% of HVAC costs – or 4.8% of total energy costs. (Let’s ignore the fact that the heating savings are less, and that cooling will not be needed throughout the year). If we throw in the ability to raise the temperature on average by 2 degrees during the day, that adds another 1.2% savings.
If we assume the worst case for lighting – that all the lights were being left on 24/7 – then lighting controls can save another 20% of energy use, maximum. That gets us up to a theoretical maximum savings, at least from HVAC and lighting controls, of about 26%.
EMS Savings in a Restaurant Environment
Restaurants have a lot more equipment than retail stores and spend a lot more on energy because of all their cooking, refrigeration and ventilation equipment, so the potential dollar savings is significantly higher. That does not mean that the percentage savings is, however.
Again using very broad averages, heating and cooling represents about 30% of a restaurant’s energy spend, while lighting represents about 18%. And, restaurants may be open longer hours. If we use the same kind of analysis as we did above for a restaurant open 16 hours per day, we would come up with a maximum savings of 3.6% of energy spend for heating and cooling and 9% for lighting – for a total of 12.6%. Of course, with a restaurant there are also potential savings from a range of other equipment, including hood exhausts, refrigeration, griddles and more.
What Should You Expect?
This was intended as a very general and simple analysis and, as indicated, there are a wide range of factors that will impact potential energy savings – not the least of which is current equipment condition and practices at a specific location
Generally, we have been seeing savings in the range of 10-15% of energy spend across all customer groups. Occasionally it is slightly lower, and, more frequently, it is higher. In fact, we have seen savings of close to 30% in a retail environment. (We have actually seen savings of up to 35% in a residential environment).
Where we have seen higher savings, it has tended to result from the fact that the EMS was able to highlight a myriad of equipment problems that caused the equipment to use significantly more energy than necessary. In some cases the problem is as simple as a temperature sensor being located in the wrong place, which results in the thermostat calling for cooling 100% of the time. Other times an HVAC unit may always be delivering second stage cooling. In one case, we found a conveyor toaster drawing power even when it was off; this issue by itself was costing over $1,000 per year, or more than 2.5% of the electricity budget.
Bottom line; be somewhat skeptical of claims of energy savings. If they seem to be too good to be true, they may very well be. Ask the vendor to demonstrate how the savings can reach that level – and ask to speak to customers who have experienced that level of savings.
Interested in learning more?