Where and how Hess’s Law work?

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You need to understand Hess’s Law of constant heat summation. Hess’s law states that energy changes are state functions.

Energy (enthalpy) changes in chemical reactions are the same, regardless whether the reactions occur in one or several steps. The total energy change in chemical reaction is sum of energy changes in its many steps leading to overall reaction. Utility Bill Tracking systems are at the center of an effective energy management program. However, some organizations spend time and money putting together a utility bill tracking system and never reap any value. This paper presents three utility bill analysis techniques which energy managers can use to arrive at sound energy management decisions.


Utility bill tracking and analysis is at the center of rigorous energy management practice. Reliable energy management decisions can be made based upon analysis from an effective utility bill tracking system. From your utility bills you can determine:

–             Whether you are saving energy or increasing your consumption,

–             Which buildings are using too much energy,

–             Whether your energy management efforts are succeeding,

–             Whether there are utility billing or metering errors, and

–             When usage or metering anomalies occur (ie. when usage patterns change)

Any energy management program is incomplete if it does not track utility bills. Equally, any energy management program is rendered less effective. When it`s utility tracking system is difficult to use or does not yield valuable information. In either case, fruitful energy savings opportunities are lost. Many practical energy managers make the smart choice and invest in utility bill tracking software. But then fail to recover their initial investment in energy savings opportunities. How could this be? This paper introduces three simple and useful procedures that can be performed with utility bill tracking software. Just performing and acting upon the first two types of analysis will likely save you enough money. It is to pay for your utility bill tracking system in the first year. The three topics are Benchmarking, Load Factor Analysis, and Weather Normalization.


Let’s suppose you were the new energy manager in charge of a portfolio of school buildings for a district. Due to a lack of resources, you cannot devote your attention to all the schools at the same time. You must select a handful of schools to overhaul. To identify those schools most in need of your attention. One of the first things you might do is find out which schools were using too much energy. Simple comparison of Total Annual Utility Costs spent would identify those buildings that spend most on energy, but not why.

Different Datasets:

You can benchmark your buildings against each other or against publicly available databases of similar buildings in your area. Energy Star’s Portfolio Manager allows you to compare your buildings against others in your region. If you can find dataset, you may also be able to benchmark your buildings against set of similar buildings. You can see the range of possibilities for your buildings. In any case, benchmarking will focus your energy management efforts and provide realistic goals for the future.

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