If you want to set realistic energy use and cost management goals, the best place to start is with the details of your current energy use and performance. That is one of the primary reasons for an energy audit of your facility. It performs two functions. First, it illustrates how the energy you purchase is used in the production of goods and services. Comparing the input energy with the useful outputs often identifies the priorities for efficiency and load management. Many firms also use on-going periodic audits to track the effectiveness of their efforts. And, wherever energy costs are crucial to a firm's competitive position, energy input per unit of production is often tracked on an instantaneous basis. For example, modern paper makers know instantly how much steam they are using to dry paper and operators can adjust the machine to minimize total production costs.
The primary objective of an energy audit is to give management an energy use overview with enough detail that they can develop overall cost control strategies. For example, most audits identify the top energy users and the likely areas for efficiency improvement. This helps management prioritize budget allocations and begin to home in on the most cost effective opportunities. However, do not confuse energy audits with design alternative evaluations. The energy audit should prioritize what the site looks at, but any one opportunity probably requires a subsequent more detailed evaluation. For example, a typical building energy audit might identify that an existing old chiller is inefficient and costly to operate. However, the broader question is to look at the entirety of the cooling situation including lighting efficiency and HVAC controls not just the decision to change out the chiller.
An energy audit should reveal the following facts:
While the temptation might be to physically measure things to answer these questions, the required instrumentation can be very costly. Start with the energy bills and work backwards trying to verify the largest users and the loads they serve. Learn how to read the electric and gas meter at your site and to subtract readings over a period of time to determine your actual use during that period. Your power company and fuel supplier may also have the ability to provide this data to you for the past few months or even years.
Lights are often one of the largest electric users and can be "counted" using some well established rules of thumb, or you could actually measure the loads by turning them all off sometime over a shutdown period to see how large they really are. You could also shut off major circuits in the building from the main panel to get some idea how large their loads are. In fact, one of the most interesting things you can do is to try to find things that are left on when everyone at the site has gone home! Always start with monthly energy use and try to think through how you used that energy. For example, the fuel consumption may be mostly in a boiler. You could read the gas meter once each day for a week to see how much fuel is used during the weekdays vs. weekends. You might also check the readings at the end of each shift if the plant operates that way.
