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| Metrix » Tuning |
A:
If you find that you have a poor correlation to weather and/or your own variables, then you have three options:
Tune to weather anyway with the lousy correlation--not recommended.
Use an average kWh/Day as your baseline with no adjustments for weather
Use 365 days of actual bill data as your baseline with no adjustments for weather
If you choose option 1, at some point in the future, you may end up risking your reputation, your company's reputation, and your client's faith in your abilities.
I personally cannot think of any reason to choose option 2, although it is theoretically correct. Metrix will allow you a baseline:
baseline kWh = coef1 * # Days
where coef1 is the average kWh/Day for the entire year.
However, if your building is in Sacramento, where you would heat in the winter (with gas) and cool in the summer (with electricity), and you were comparing baseline usage to actual post-retrofit bills, Metrix would find that you save huge amounts of electricity in the winter, and that your building is using more electricity in the summer--all because you are comparing to average usage per day. Your baseline would be the same for January and July, but usage of course would not. If you only give yearly reports, this option may do, but if you give quarterly reports, the reports would mean nothing to the customer, only yearly numbers would be of any value. A report of July-August-September would most likely show that the customer is using more energy in the current period than in the base year. The customer would never know if savings were occurring or not until the end of the year--and all the pluses and minuses are added together.
Note with a baseline dependent only upon number of bill days, gas savings looks high in summer and there is negative savings in the winter.
The third option is the best (when you get bad correlations between weather and usage). The third option involves:
- putting the tuning screen into "manual"
- zeroing out all coefficients. (make sure you do step a and b for all applicable TOU periods and for demand too, if necessary)
- in the modifications view, add a modification
- open the modification, and choose the third "specification option"
- open "factor history" and make sure that the bottom left hand field corresponding to the 365 days for which you want to bill match. They will by default correspond to the dates chosen in the tuning screen.
The reason I prefer bill matching is precisely the same reason option 2 is not satisfactory. You can compare any month's current and tuning period usage, and will be able to see if your savings is on track or not. A quarterly report actually has value in itself, and the customer will be able to see if you are saving energy or not. Also, this third option is the simplest to explain to the customer.
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