Plug Load References for Energy Modeling
Plug Load References for Energy Modeling
Plug loads—everything from computers and copiers to coffee makers and vending machines—can represent a surprisingly large slice of a building’s energy pie. When you don’t have detailed equipment schedules or measured data, industry-standard references can help you make reasonable assumptions typically accepted by rating authorities.
It’s important to get your plug loads as accurate as possible. Apart from being a major source of energy consumption, plug loads influence equipment sizing, airflow, and psychrometrics. More than that, if plug loads are equal between your proposed and baseline model (think LEED), oversized plug loads will decrease your net savings. So you’ll want to get them right—and use a source your reviewer will accept (especially if your values are lower than expected!).
Here are a few go-to sources for plug load data that are commonly accepted by rating authorities:
1. ASHRAE 90.1 User Manual (Table G-C)
The ASHRAE 90.1 User Manual is often the first stop for modeling practitioners. Table G-C provides recommended equipment power densities (W/ft²) for dozens of space types—everything from offices and classrooms to retail and healthcare. It also includes occupant densities and service hot water allowances, making it a one-stop resource for many baseline assumptions.
2. COMNET Modeling Guidelines & Procedures (Appendices B & C)
The Consortium for Energy Efficiency’s COMNET program offers a free Excel workbook with plug-load densities by building type (Appendix B) and internal load schedules (Appendix C). This is ideal for pulling in whole-building loads and realistic hourly profiles. A free account is required to download:
3. ASHRAE Fundamentals & AEDGs
Chapter 18 of the ASHRAE Fundamentals Handbook contains detailed plug load tables—especially helpful for office and lab spaces. The ASHRAE Advanced Energy Design Guides (AEDGs) offer standard- and high-efficiency load assumptions. For time-varying profiles, ASHRAE Research Project 1093-RP includes hourly plug-load schedules for more realistic modeling.
4. LEED v4.1 Reference Guide for BD+C – Appendix B
Appendix B of the LEED v4.1 Reference Guide provides receptacle load densities (W/ft²) by space type and offers modeling guidance for both baseline and proposed cases.
Download the full guide:
LEED BD+C Guide PDF
Also available is the essential Excel-based:
v4.1 USGBC Data Import Spreadsheet, which includes:
- Appendix B inputs for proposed models
- Appendix G assumptions for baseline models
- QC checklists to streamline LEED reviews
5. ENERGY STAR MFHR Simulation Guidelines
For residential projects or those earning credit for ENERGY STAR appliances, these guidelines provide:
- In-unit plug loads: 0.5 W/ft² at 5.8 hrs/day
- Common-area plug loads: 0.2 W/ft² at 9 hrs/day
- Detailed appliance and schedule assumptions
Download the simulation guidelines:
6. CIBSE Guide F & UK National Calculation Methodology (NCM)
For UK projects, CIBSE Guide F includes small-power benchmarks for offices and labs. The UK’s National Calculation Methodology (NCM) provides compliance-grade plug-load data.
7. Canada’s MNECB
The Model National Energy Code for Buildings (MNECB) includes receptacle power densities by space type—especially useful for projects under Canadian federal or provincial energy codes.
Final Tip: Always apply professional judgment and adjust plug load values to match your project's actual equipment and use patterns. By leveraging these vetted sources, you’ll build realistic, defensible plug-load profiles that satisfy both owners and rating authorities.