Welcome to Lesson 4 of the course titled energy audit modeling. The previous lesson explained how to create the energy model, and this lesson will summarize how to calibrate the energy model to match actual utility bills.

The first main idea to take away from this lesson is that we are calibrating to the units of energy not dollars. This is the time that we focus on accurately predicting the energy consumption of the building. Later we will be looking at dollars saved for each energy efficiency measure.

The next important piece is to use actual monthly energy bills. We are not interested in total annual energy. For accuracy, we want to know that our model correctly predicts energy consumption for each month. This lesson will also discuss how to choose which variables should be used in calibration. These are the inputs that have to be changed to get the model to match.

When entering the calibration process, it is important to keep in mind the original goals of the energy model, and the energy audit in general. This will help keep us from spending too much time on things that are not going to help accuracy in our final recommendations.

First, focus the effort on lighting and HVAC. If you are also evaluating envelope changes, keep those in mind as well. Most importantly, the inputs that we modify for calibration cannot influence the energy efficiency measures that we are going to evaluate next. For example, if we change the efficiency values for the existing HVAC equipment to get the model calibrated, then any results of evaluating equipment replacement will be very inaccurate. This may seem like an obvious example, but there are cases you may run into that are not as obvious.