The model you need to develop for EAc1 is the same as for EAp2 unless you’re on a district energy system. In that case, projects must show that the building can meet the prerequisite (14% reduction for new buildings) by 

itself, without the efficiencies of the district plant. 

Some energy-modeling software tools have a daylight-modeling capability. Using the same model for both energy and EQc8.1: Daylight and Views—Daylight can greatly reduce the cost of your modeling efforts.

Besides energy modeling, you may need to use the exceptional calculation methodology (ECM) when any of the following situations occur: 

The energy software cannot carry out calculations for a specific system like natural ventilation or unusual HVAC equipment.
Process loads are different in baseline and design cases and can influence total energy cost savings.
The proposed design can’t demonstrate savings with the modeling protocol and needs additional calculations. 

The energy model itself will not account for any change in plug loads from the baseline case, even if your project is making a conscious effort to purchase Energy Star or other efficient equipment. Any improvement made in plug loads must be documented separately, using the exceptional calculation methodology (ECM), as described in ASHRAE 90.1-2004. These calculations determine the design case energy cost compared to the baseline case. They are included in the performance rating method (PRM) table or directly in the baseline and design case model. 

LEED divides energy-using systems into two categories:

Projects generating renewable energy onsite should use Option 1 to best demonstrate EAp2 compliance and maximize points under EAc1. Other options are possible but won’t provide as much benefit. Like any other project, model the baseline case as a system compliant with ASHRAE 90.1-2004, using grid-connected electricity, and the design case is an “as-designed” system also using grid-connected electricity.

For existing buildings, the baseline energy model can reflect the pre-renovation features rather than a minimally ASHRAE-compliant building. This will help you achieve additional savings in comparison with the baseline.

Energy modeling can inform your project team from the start of design. Early on, review site climate data—such as temperature, humidity and wind, available from most energy software—as a team. Evaluate the site context and the microclimate, noting the effects of neighboring buildings, bodies of water, and vegetation. Estimate the distribution of energy across major end uses (such as space heating and cooling, lighting, plug loads, hot water, and any additional energy uses), targeting high-energy-use areas to focus on during design.  

Use simple computer tools like SketchUp and Green Building Studio that are now available with energy analysis plug-ins to generate a first-order estimate of building energy use within a climate context and to identify a design direction. Note that you may need to refer to different software may not be the one used to develop complete the whole building energy simulations necessary for LEED certification.

The architect, mechanical engineer, and lighting designer need to familiarize themselves and confirm compliance with the mandatory requirements of ASHRAE 90.1-2004, sections 5–9.