Same-Day Adjustment Design: Additive vs Multiplicative

Why same-day adjustment exists

Same-day adjustment exists because historical candidate-day baselines often miss the operational context of the event day itself. If the site, fleet, or program participant begins the day materially above or below what the historical average suggests, reviewers need a controlled way to reconcile that difference before judging event performance.

The challenge is that the correction must remain transparent. If the adjustment becomes too aggressive or poorly bounded, the baseline stops being a reference and starts becoming a model fit.

Additive vs multiplicative reasoning

Additive SDA is often easier to explain when the adjustment should behave like a fixed delta applied across the event. Multiplicative SDA can be more intuitive when proportional scaling is desired, but it also raises more questions about caps, factors, and what constitutes a reasonable ceiling.

In practice, the right choice depends on the load shape, the customer class, and how event reviewers think about operational realism. GridMango now supports the richer SDA model directly so teams can document those tradeoffs instead of hiding them.

Bounds, factors, and reviewer trust

Bounds should be treated as governance controls, not cosmetic settings. If teams cannot explain why upward or downward caps exist, or why multiplicative factors are so permissive, they are unlikely to survive serious settlement review. The safest pattern is to define the adjustment window clearly, keep caps understandable, and preserve audit outputs that show exactly what happened.