Getting into the nuts and bolts of energy usage.

Energy costs represent a big chunk of a building's operating budget.

An upgrade in a building system or the need to replace a failed major component, such as a chiller or boiler, can often prompt a fresh look at energy use. In many cases, system upgrades offer an enormous opportunity for savings.

In particular, building owners must maximize the efficiency of design, maintenance and operation of their core systems: mechanical systems, lighting and controls.

The good news is that numerous improvements have been made in these technologies over the years, both in terms of reliability and cost-effective operations. A feasibility study is the first step toward developing a comprehensive, long-term solution--one that can pay for itself over time with energy savings.

The feasibility study provides a realistic overview of a building's existing systems, energy performance, needs and opportunities for savings. An essential component of the process is a utility analysis, which calculates rate structures, costs and usage of electricity, fossil fuel, water and sewer utilities for a selected base year and displays these data on a series of charts and graphs. Data are obtained from actual billing information. Utility costs are allocated both by type and BTUs per square foot.

Energy comparison ratios, such as BTUs per square foot, can be important indicators in calculating and verifying potential utility savings. In fact, these comparisons can yield a great deal of information before even setting foot in the building.

For example, a high load factor with a high kilowatt-hour (Kwh) per square foot may indicate that most of the equipment is operating around the clock, whereas a low load factor with a high Kwh per square foot may show that some equipment is turned off, but there is still too much energy being consumed when the systems are operating.

A high load factor with a low Kwh per square foot could mean that absorption chillers or other mechanical systems are maintaining steady, but low Kwh consumption. A low Kwh per square foot with a low load factor may indicate the building is turning off equipment when it is not needed and is correctly controlling its HVAC systems, indicating that engineering time would be better spent on other opportunities.

Two particularly useful comparisons are the effects of weather on energy usage and the load factor, which is the ratio of consumption (Kwh) to demand (kW).

Energy usage intensity in BTUs per square foot, when superimposed on a graph of degree-days, shows the effects of weather on energy usage.

One useful way to view this information is to observe the spring and fall months, when cooling degree-days and heating degree-days cross over. This shows if outside air economizing has taken place during those months when "free cooling" is available.

Another use of this information is to determine the base load for gas and electric usage. The load factor is important in identifying building energy use patterns over the course of the year.

Moreover, segregating load into lighting, fan motors, cooling and miscellaneous equipment yields an "end use profile" that is very important in identifying system inefficiencies and thus areas of potential savings. A thorough analysis will also compare the facility's energy usage data against normalized and actual monthly degree-days from the 30-year average climate summary (1961-1990) to normalize "spikes" that may be related to hotter or colder than normal years in a particular location.

The results of the feasibility analysis consist of the utility analysis along with a broad outline of needs for system redesign, replacement or upgrades, projected implementation costs and projected savings.

Based on this information, owners may choose to move forward with a preliminary engineering study.

This step defines opportunities and projected costs in more detail, including a detailed inventory of all systems, components and controls; work sessions to discuss the facility's needs and priorities; "order of magnitude" costs (approximately 20%); projected payback; financing options; and pre-engineering design.

The information can also be used to create or update long-term formal facility and energy master plans, which help to identify more timely and cost-effective ways to accomplish capital projects.

A clear identification of existing conditions, needs and priorities will form the basis for a long-term solution involving one or more system upgrades, either as part of a single project or phased in over a period of time.