Checking Performance Targets

How do you know if the conservation measures are working? Let's look back at our example.

The customer came in with a "high bill complaint" -- he knew something was wrong. Here was his operations or "tuning" graph:

Looking at the graph, usage is not that high during most of the year -- this customer's problem was with heating. But no one knew that at the time -- so he was given a lighting upgrade.

Not surprisingly, a year later the customer came back. He wanted to know if the lighting measures were working because he had not seen much savings. Now that we know what was going on in this building, we can show the customer how well (or poorly) he is doing.

For that purpose, we use the simulation model to predict what the customer should have consumed after the lighting retrofit. Then we can compare that prediction to the actual monthly bills and see if we are on target. For a valid comparison, we run the model using the same weather and operations that occurred during the post-retrofit year. That way the predicted and actual bills are directly comparable.

 Here's what the operations plot looked like for the post-retrofit year:

As you can see, the building is behaving very much as predicted. The points have dropped to a new curve. Here is what the monthly billing data look like:

In this plot, the black line shows what the old building would have used under the same conditions. The blue and red bars show predicted and actual monthly bills. There were a few "noisy" months but generally the conservation measures appear to be performing as expected. We call this type of plot the "Commissioning Report" because it provides a simple commissioning check at low cost.

What can we tell the customer? The good news: the lighting measures are performing as expected and delivering the appropriate savings. The bad news: those savings are small because the real problem was with the heating system. If we had applied EZ Sim when the customer first came in, we could have done a better job of helping him.

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