why energy analysis is cloudy without weather data

Why Energy Analysis Is Cloudy Without Weather Data

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We all know the weather affects the energy consumption of a building.

But how much? 90%? 50%? 10%?


One way to get a quick idea is via the U.S. Dept of Energy’s extensive CBECS database, the result of surveys of tens of thousands of buildings.

Our CBECS interface is free:www.BuildingBenchmarks.com


Cooling is 7% of electricity usage


Heating is 97% of gas usage


Overall, weather loads are 43%

(47 kbtu/sf) of the 110 kbtu/sf

annual total


OK, 43% of the total energy bill.

How much can that vary year-to-year?

Enough to cause pain in my budget?


Here’s the degree day report from free www.WeatherDataDepot.com


That’s bound to get someone’s attention!

The weather impact on building energy usage is significant and can be analyzed quite easily.

48% increase in degree daysx weather load of 43%

21% budget impact


Degree Days is a weather metric that’s only useful in the context of building energy usage.


How are degree days calculated?

1. Set a balance point temp, the outside temp that divides heating and cooling.

2. Calculate the daily difference between balance point and mean daily temp.

3. Track heating separately from cooling.


Why bother with degree days?

Why not use the simpler concept of average monthly or average annual temperature?


High Low Mean HDD CDD

San Diego

Day 1 65 55 60 0 0

Day 2 65 55 60 0 0

Average 60

Denver

Day 1 90 60 75 0 15

Day 2 60 30 45 15 0

Average 60

These cities had the same 60F average temp for two days. Was building energy

usage the same?


The average annual temperature in San Diego is 65F. The average annual temperature in Dallas is 65F.

In Dallas, annual A/C usage is 160% more and annual heating use is 350% of San Diego. How can that be?

The average annual temperature in Orlando is 72F. The average annual temperature in Phoenix is 72F.

In Phoenix, annual A/C usage is 63% more and annual heating use is 100% more than Orlando.

Huh?


Conclusions:Use Degree Days because this method tracks heating and cooling needs separately

Average monthly or average annual temperature doesn’t work–the warm and cool days cancel each other out.


What information does WeatherDataDepot give me?


1. Monthly Degree Day Comparison Report


2. Cooling and Heating Cumulative Trends


3. Monthly Trends


4. Drill down to Daily Data


5. Copy to Excel


6. Degree Day Forecast, next 14 days


7. Extensive FAQs


8. Your Own Personalized Link


9. Station Location and Excel File


What about humidity, cloud cover, wind velocity?

Huge increase in data cost and computational complexity

Historical and current data for many fewer sites

No significant analytical improvement


Presented by EnergyCAP, Inc.EnergyCAP is used by organizations that receive many utility bills for bill processing, energy reporting and analytics

Over 30 years as industry leader; first release in 1982. (The predecessor software was FASER Energy Accounting).

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why energy analysis is cloudy without weather data

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