This appendix summarizes several years of utility metering data and billing data for 925 L Street. This purpose is to establish baseline energy use against which energy savings due to measures taken in response to IMDS data can be evaluated.

The following data were provided to LBNL:

• Monthly gas utility bills dating back to January 1999. Gas use by calendar month was estimated from billing months.
• Summary gas and electric data dating back to 1996 - days per billing cycle were not included, data were of limited use
• Monthly electric billing data from August 2000
• Monthly electric billing data for one floor that is metered separately, dating from October 2000.
• 15-min whole-building electric demand data dating back to 1996
• 15-min chiller demand data dating back to 1996. The chiller power meter was installed by SMUD under a different program. The meter was commissioned by a SMUD technician and found to be off by a factor of 3, and the data were adjusted to reflect this.

There are some changes that will have to be accounted for when using the baseline data to evaluate savings:

1. The 2001 energy crisis prompted some permanent reduction measures, and could possibly have altered tenant behavior. It was noted by the operations staff that when they started to return lighting in some areas to previous illumination levels, they received complaints from tenants who still thought it was wasteful. Other than the installation of the heat exchanger, this is the only explanatory information we have currently for the reduction in energy use between 2000 and 2001 as seen in Figure 1.
2. One floor is metered separately. The floor receives some shared services, such as ventilation. In the past this floor has not been occupied and only received services when requested. The separately metered space is 12,225 (12,168 used in Enflex Calcs) square feet out of a total of 168,000. Billing data for 2000-2002 for this floor were provided by SMUD.

Annual Energy Use

Figure 1 shows the change in annual energy use on the main building meter between 1996 and 2002. Similarly, Figure 2 showns the corresponding data for the combined chiller usage. Note that whole-building electricity use increased in 1999 at the same time as chiller electricity use dropped. This is likeley due to major changes in building occupancy and schedules and a chiller replacement at that time.

Annual gas usage between 1999 and 2002 are given in Figure 3. Gas usage increased in 2001 and 2002. From Figure 4 it is evident that summertime gas usage has increased dramatically. Figure 4 shows gas and electricity use by month for the same period.

Figure 1. Annual Energy Use by Year, Main Meter

Figure 2. Annual Chiller Energy Use by Year

Figure 3. Annual Gas Usage by Year

Figure 4. Breakdown of Total Energy Use

Weather Sensitivity

Temperature data were taken from an archive of average daily temperatures for the city of Sacramento. This archive is located at http://www.engr.udayton.edu/faculty/jkissock/weather/. Hourly temperature data were purchased from the National Weather Service for peak demand analysis under a separate project. The weather station is located at the Sacramento Executive Airport. Figure 5 uses data from University of Dayton and Figure 6 uses the purchased data.

Figure 5 shows the relationship between weekday total energy use and average outside temperature, using University of Dayton temperature data, for 1996 to 2002. Statistically it is not a very strong correlation; however, this is still useful in understanding the general trend in energy usage with respect to temperature.

Figure 6 shows a similar graph, using only the Summer peak hours; ie, 12-5pm, June 1 through September 30, 2000. The "Daily Average Temperature" is thus the average of only the hours 12-5pm. This shows a much stronger correlation, which is expected for the warmer months. Figure 7 shows chiller electricity use by month versus temperature.

A significant increase in summertime gas use is evident in 2001 and 2002. The reason for this is not known but warrants further investigation. Figure 8 shows monthly gas use vs. monthly average temperature. For the years 1999-2000, there is a strong heating slope. The cooler months in 2001-2002 follow the same linear trend as for 1999-2000; however, the warmer months do not. Thus the increase in gas use is not likely due to cooler summer temperatures.

Figure 5. Whole Building Energy vs. Outside Air Temperature

Figure 6. Daily Peak Load vs. Outside Temperature, Summer Peak Hours

Figure 7. Monthly Chiller Electricity Use vs. Outside Temperature

Figure 8. Monthly Gas Use vs. Outside Temperature

Baseline and Savings Analysis

The operations staff first began to use the IMDS system in mid-2002. At this point there has not been sufficient time to observe the system or to expect any energy savings due to the IMDS. In the pilot IMDS, even after a year of monitoring and ample discovery of savings opportunities, no significant savings were realized until after the project's end, when the building staff upgraded the control system and began to implement recommendations.

The 2001 data, due to California's energy crisis, may not be a good representation of baseline operation. Using 1998 and 1999 may overestimate savings as energy use was higher in those years. Basically a savings analysis may require a more advanced analysis than used in evaluating the previous IMDS, ie, it will need to adjust for other factors affecting energy use besides temperature variations.

Cost Data

Two years of cost data were available for both electricity and gas use. Electricity costs during this time, for peak and off-peak periods, were relatively stable as shown in Figure 9. In constrast, gas costs for Winter 2001 were extremely high. This is reflected in Figure 10 and Figure 11, which give monthly costs per kWh and per therm respectively.

Based on this data, the average annual expenditure for the main building account is nearly $243,000, or $1.6 per square foot per year, based on 147,750 square feet, and nearly $29,000, or $2.4 per square foot per year, for the 12th floor, based on 12,250 square feet. Combined, the total cost is $271,000, or $1.7 per square foot per year. On the gas side, annual costs are $70,000, or $0.45 per square foot per year.

Figure 9. Average Utility Cost per Day, by Fuel and by Month

Figure 10. Average Electricity Cost per kWh, by Month

Figure 11. Average Gas Cost per Therm, by Month

Peak Loads and Demand Reduction

Since 1999, the annual/summer extreme peak loads have come down slightly (Figure 12) and the typical daily peak load dropped when the chiller retrofit was completed in 1999. The plots shown in Appendix Y summarize the past seven years of hourly data for whole building power and chiller power. These indicate a decrease in typical full-load operation.

In light of recent events relating to California's energy supply, peak loads are of great interest. As part of a separate project evaluating demand shedding programs, analysis of peak loads at 925 L Street was done.

Figure 13 illustrates the load reduction potential for the peak day, June 14, in 2000 according to a ten-day baseline. Typically these are calculated hour by hour, so this example uses only the hour 16 (4-5pm). The demand on the peak day was about 750 kW, and the average demand during the same hour for the previous ten days was about 600kW. Thus, if 925 L had been a participant in a demand shedding program and had been requested to shed load, a 150 kW reduction would have been necessary to meet the baseline. Any additional reduction below the baseline would have been considered curtailment.

Note that the peak day represents an extreme situation; on other demand reduction days, the amount of curtailment would likely be less. Although, to our knowledge, 925 L has no intention of participating in a demand reduction program, pre-cooling and other peak load management strategies could be used during extreme heat and energy usage periods.

Figure 12. Annual Peak Load by Year

Figure 13. Demand Reduction Scenario