Placing dataloggers and using existing control points seems easy enough, but converting these inputs into savings numbers can sometimes prove to be outside of the scope of the facility manager s skillset. Excel will give regressions, fit line equations, and statistical indicators which show how well your usage is represented by the fit line. This works if you have a simple variable that quantifies your production. Since most facility managers are already tracking their utility bills, it is only one additional small step to see whether you have saved any energy and costs from your energy management program. CONCLUSION Weather changes from year to year. We will call this year the Base Year. However, it is difficult to find the best balance point in Excel, as you can in specialized software. Excel may force you have to choose just one balance point, and possibly then you would iterate with different balance points, whereas canned software will allow you to easily find the best fit line using different balance points. In addition, if you enter your weather data in high low temperatures or average temperatures, it can be difficult to apply the correct weather data to the correct billing periods. But, since we are trying to keep this paper at an Threaded Rod Astm introductory level, we will use the word Savings. This paper presents the how and why of weather correction for those who want to become more familiar with the concepts and methodology. You need to know where you are, where you were, where you are going, and how where you are now fits with expectations of your progress. The Best Fit Line then represents the utility bills. However, if your printer manufacturing unit was served by a different meter or submeter than the other units, then you could use the number of printers produced as a variable for the meter (or submeter) that serves the printing unit. This is done using weather correction as shown below. We call this usage that is determined by the Baseline Equation, Baseline Usage. Remember, the Baseline Equation represents how your building used to use energy in the Base Year.) Most likely, the simplest and most palatable method for the facility manager to determine whether you are saving energy is Option C, comparing utility bills. If wish to use utility bills to show energy savings from energy management programs with any degree of accuracy, it is important to correct your utility bills for fluctuations in weather. Just compare prior year bills to current year s bills, and you will see if you have saved. Well, it isn t that easy. We used the equation: Savings = last year s usage this year s usage When we use weather correction, we end up with Figure 5, and use the equation: Savings = How much energy we would have used this year how much energy we did use this year** **where this year s usage from the 1st equation is the same as how much energy we did use this year from the 2nd equation The next question is, how do we figure out how much energy we would have used this year. CANNED SOFTWARE Weather correction can be done in Excel, however it can be laborious, and oftentimes may not be as rigorous as when done using specialized software. Determine whether your meters are on the best rates Check to see if you are being billed correctly by the utility Create bills for your tenants (if you have any) Determine whether you have saved any energy from your energy conservation measures Aggregate your usage and costs and pass this aggregated data to potential energy suppliers Create utility budgets More generally, if you keep aware of the state of your utility accounting, you will know where your facility is and how it is faring towards your goals. The blue dots represent the utility bills. In this example, we would select the year of utility data before the installation of the chilled water system. For example, an automobile manufacturing plant can track number of automobiles produced. When we tried to compare last year s usage to this year s usage, we saw Figure 3, and a disastrous project. Many in our industry do not call the result of this comparison, Savings, but rather Usage Avoidance or Cost Avoidance. The Best Fit Line Equation, which represents the Best Fit Line, which in turn represents the Base Year of utility data. As shown in Figure 6, we graph Base Year usage versus weather (in the form of Cooling Degree Days or Heating Degree Days). We can tell it is the Best Fit Line by looking at some statistical indicators (such as R2 value, Net Mean Bias Error and CVRMSE, which are not covered in this introductory paper) . This would typically be the year before you started your energy efficiency program, or the year before you, the new facility manager, were hired, or some chosen year. WEATHER CORRECTION IN EXCEL VS. In order to correctly navigate your airplane, you need to understand where it is, where it was and where it is going. First, we select a year of utility bills we want to compare future usage to. How? You take a bill from some billing period after the Base Year. Correcting utility bills for weather data will give more accurate representations of savings that were accrued. Now, to get a fair comparison of this year versus last year, we compare: Savings = How much energy we would have used this year How much energy we did use this year or if we change the terminology a bit: Savings = Baseline Energy Usage Actual Energy Usage where Baseline Energy Usage is calculated using the Baseline Equation and current month s weather and number of days, and Actual Energy Usage is the current month s bill. The major desktop programs are Energy CAP, Metrix, Stark Essentials, and Utility Manager Pro. Both equations are one and the same, Baseline = How much energy we would have used this year, and Actual represents how much energy we did use this year. Merely comparing utility bills can yield inaccurate indications of the amount of savings from energy management programs due to the unaccounted influence of weather or other factors. You (or your software) plug in the number of days and the number of degree days from the bill into your Baseline Equation. Let s recap what we have done: We graphed a Base Year of utility data versus weather data We found a Best Fit Line through the data. It is the same with energy management.Article Source: 1ArticleWorld. So, with the new inputs of number of days and number of degree days, the Baseline Equation will tell you how much energy the building would have used this year based upon Base Year usage patterns and this years conditions (weather and number of days). Why? Well, although some utility managers do present calculations given to them by the friendly sales rep, this method is hardly reliable, as they may produce inflated numbers. You can wave your hands in the air, and decide upon a number; calculate your savings based upon data logger and control points; compare utility bills to determine savings; and finally, employ a building model. (These are referred to as Option A, B, C and D in the IPMVP, FEMP Guidelines and other literature. Building modeling, while it can be useful, requires hours of time to construct the model, and may represent how much the building should be using, and may not really represent what the building truly is using. Plus, in the end, it is all about the utility bills, as the bills reflect how much you are paying. Nearly all of them will correct for your own variables as well. AVAILABLE WEATHER CORRECTION DESKTOP SOFTWARE All of the major desktop utility bill tracking software packages will now correct for weather data. The Fit Line Equation represents how your facility used energy during the Base Year, and would continue to use energy in the future (varying with changing weather conditions) assuming there were no significant changes occurred in building consumption patterns, such as new equipment, area or operating hours. Why would he write that? An energy accounting system is much like an airplane s control panel. With utility bill tracking systems, Energy managers can: Enter target usage and costs and track their actual performance against their targets Discover large increases in energy usage and take corrective actions Identify the buildings that are using more SQFT than the others, and concentrate energy management activities on those buildings. Abraxas Energy Consulting performs energy audits ( http: abraxasenergy energy-audits. This Best Fit Line has an equation, which we call the Fit Line Equation, or in this case the Baseline Equation. How much did we save last year? Is that more than what we pay our energy manager? Did your recommendations give reasonable paybacks? Why do we even have an energy manager? There are several methods to determine whether you have saved energy from your energy conservation efforts, as described in the literature.ABSTRACT Utility bill tracking is at the heart of an effective energy management program. CORRECTING FOR OTHER VARIABLES Facility Managers in the industrial sector may want to correct for production rather than (or in addition to) weather data. The Best Fit Line is the line that comes closest to all the utility bills as shown in Figure 6. Try it, and you will see.php ) and provides utility bill tracking, energy auditing, measurement and verification, retro-commissioning, utility bill auditing and other energy management services for its clients world-wide. If your factory makes several different things, for example, disk drives, desktop computers, printers and main frame computers, it is difficult to come up with a single variable that could be used to represent production for the entire plant. Once we have this equation, we are done with this regression process. Then we find the Best Fit Line between usage and weather. If those objections hold, that leaves utility bills as the last remaining method to quantify your performance as an energy manager. WHAT UTILITY BILL TRACKING CAN DO FOR YOU Jim Faes from Jefferson County School District wrote to me energy accounting is the backbone of our school district s energy management program. HOW WEATHER CORRECTION WORKS Rather than compare last year s usage to this year s usage, when we use weather correction, we compare how much energy we would have used this year to how much energy we did use this year. Let s find out why. UTILITY BILL TRACKING: THE REPORT CARD FOR FACILITIES AND FACILITY MANAGERS Energy Managers and some Facility Managers all to often have to justify their existence to management. Base Year bills Best Fit Line = Fit Line Equation In our example: Baseline Equation = Fit Line Equation Once you have the Baseline Equation, you can determine if you saved any energy. You can find information on all of them online. If you fly the plane without the control panel, you have a good chance of crashing the plane

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