Energy markets fluctuate wildly. An "UPD" version will revise the default escalation rates for electricity, natural gas, and oil. Recent updates have begun factoring in the volatility of renewable energy integration and carbon taxes.
Post-2020 updates typically refine how the model handles variable-speed drives (VSDs) and equipment that cycles on/off frequently (like inverter heat pumps). Older line-load models often overestimated energy use for modern equipment. ashrae 904 pdf upd
ASHRAE standards are proprietary and typically require purchase, but there are two primary ways to access the text: Energy markets fluctuate wildly