A "de-rate" is the haircut applied to a data center's nameplate power capacity to reflect what the regulatory rules actually let it run continuously. A 400 MW interconnection on paper is not 400 MW of delivered capacity. Once you subtract the federal RICE NESHAP rule (an EPA air standard that caps how many hours per year backup engines can run), state air-permit guidance like Virginia DEQ APG-576 (a Virginia regulator memo on what large engines must install to control emissions), and the curtailment frequency implied by a non-firm or interim non-firm transmission agreement (utility contracts that let the grid operator shut you off when the wires are full), the effective MW is often 20 to 30 percent lower. Most underwriting models do not price this. The developer finds out at interconnection agreement signature, or worse, at commissioning.
The Cliff de-rate calculator does this math per Point of Interconnection (the specific substation a project ties into). Pick a state, pick a technology, enter the location and the requested MW, and the calculator combines the federal annual hour budget for backup engines, the state air-permit cap on how many hours that equipment can run, the major-source federal operating permit overlay (Title V, the program that kicks in once a site exceeds national pollution thresholds) if applicable, and the curtailment frequency implied by your transmission service class. The output is a single effective MW number with the math shown. Runs in under a second.
The math itself is arithmetic. What is AI-native is the input layer underneath. APG-576 is a guidance document, not a structured database. PJM’s non-firm transmission product definitions (the Mid-Atlantic grid operator's rules for interruptible service) live in tariff language that changes as federal energy regulator orders land. Five years ago a calculator that pretends to do this would have had to hire a regulatory team to maintain the assumptions. Today the assumptions update themselves from the same live regulatory docket corpus that Cliff’s regulatory intelligence layer ingests every day.
Run it on your own site at /de-rate/calculator, or read the walkthrough at /de-rate/how-it-works.
Get started
Type your site in. See the de-rate.
The calculator returns an effective MW number, the binding rule, and a $/MW-yr net value as you type.