For data center developers: The De-rate calculator

Effective MW, binding rule, net value.

Site

State

Interconnection product offered

Load and generator fleet

IT load at POI (MW)

Generator fleet nameplate (MW)

Aggregate backup gen across the campus, including N+1.

EPA tier

Fuel

Expected runtime hours

Curtailment p50 (hrs/yr)

Median expected. e.g., 6 events × 6 hrs.

Curtailment p90 (hrs/yr)

Worst-case stress test.

Maintenance + testing (hrs/yr)

Expected true outages (hrs/yr)

State emergency definition

Treat curtailment as 'emergency' under Virginia air permit?

Post-APG-578, Virginia DEQ conditionally treats utility outages noticed within 14 days as emergencies. Pre-memo, only acute outages qualified.

Live result

No peak de-rate

Nameplate

500 MW

Effective MW (peak)

500 MW

Air permit covers expected curtailment

Binding constraint

RICE NESHAP non-emergency budget (100 hrs/yr)

The federal RICE NESHAP non-emergency cap is the closer ceiling. State permit headroom is larger but is not the binding rule.

Title V NOx

224 t/yr

Triggered

Compliance

$7,000/MW-yr

Net value

$173,000/MW-yr

Directional model. Not legal advice. The full report below cites every rule on every line.