What is a Utility Bill Analysis, and why is it important?
For the purpose of energy audits and studies, a Utility Bill Analysis (UBA) is a statistical analysis of your bills, looking for trends and breaking out into different components (heating, cooling, baseload, etc.).
Done correctly, it gives the following:
- A benchmark to compare your building against other buildings.
- A baseline of existing.
- The foundation of energy conservation.
- Trends and anomalies.
Why Perform a Utility Bill Analysis?
As the famous management guru, Peter Drucker said, “What gets measured, gets improved.”
This is a fairly blunt tool, but it can help you focus your efforts on the most energy-intensive buildings. The simplest way to do this is to add up 12 months of utility bills (electricity and fuel), convert to a common unit of energy (we use ekWh or equivalent kWh) and divide by the building area. I have seen buildings range from less than 10 ekWh/ft2 (ultra-efficient multi-res) to more than 100 ekWh/ft2 (inefficient hospital). The important part is that you compare your building against other buildings of similar use and location.
Create a Baseline
This is a statistical analysis (multi-variable regression analysis) that turns your consumption into an equation. This equation might look like this:
Consumption [kWh] = Base Load + Summer Extra + Winter Extra, or
Consumption [kWh] = 1,000 [kWh/d] x days [d] + 5 [kWh/cdd(15)] + 10 [kWh/hdd(18)]
The three variables used are the number of days, cooling degree days base 15 and heating degree days base 18. Although complicated looking, it simply says that the consumption for a given period is dependent on the number of days and the temperature for each day. Other independent variables can be added such as production (number of widgets), ice rentals (for an arena), school days, etc. Statistically, there would be other numbers that would tell you how good of a fit each variable is (T-Stat) and the overall equation (regression – R2).
Foundation for Energy Conservation
The baseline helps to break out the energy use into different consumptions. For example, the baseload on a natural gas meter could be for domestic hot water, and the winter extra could be for the heating boilers. The baseline would then be used to create the consumption for a typical year. This is very important because you don’t want to base your savings on an abnormally cold winter or hot summer. (Unscrupulous people will do this when it benefits their product or service.)
Trends and Anomalies
Just looking at the utility bill analysis can often find savings. For example, a sudden jump in consumption may be from a change in the control of a large motor. Or a consumption that is “loosely scattered” around a regression line could mean sloppy controls. Years ago, the City of Hamilton undertook utility bill analyses of their facilities and found an anomaly in an arena. After testing, they discovered a faulty meter resulted in being overcharged on their bills. The utility had to repay them over $1M.