Reading negative capacity values

A negative published capacity estimate is a reason to investigate the underlying calculation. It does not, by itself, establish that equipment is currently overloaded or that a particular new load cannot be served. Equally, an apparent data limitation is not evidence that the utility can accommodate the project.

Read the subtraction before interpreting the sign

PSE&G's New Jersey EV Hosting Capacity Map describes its calculation as a circuit's maximum load value less its peak load in the current or previous year. It also says the load inputs are raw exports, without completed adjustments for weather, meter error or distributed energy resources.

Under that calculation, a negative result means the peak-load input exceeds the maximum-load input. That is the arithmetic finding. Diagnosing an equipment constraint requires establishing what those inputs represent, which period they describe and whether the utility has identified a relevant limitation.

A possible explanation is not a diagnosis

Weather, data quality, network configuration and assessment assumptions can affect a published value. A single negative observation does not identify which factor is responsible. Repeated observations can show persistence in the published record, but do not by themselves explain the engineering cause.

Do not use a change in generation hosting-capacity methodology to explain a load-serving value without evidence that the same change applies. Generation exports and customer demand can be assessed under different operating conditions.

Turn the finding into a project question

• Which equipment and assessment period does the value describe?
• What do the maximum and peak inputs mean, and are they comparable?
• Has the utility confirmed a constraint, or is the value awaiting clarification?
• When does the relevant equipment peak, and how would the proposed load coincide with it?
• What further assessment would determine whether upgrades or an agreed operating restriction could accommodate the project?

A load with a different operating profile may warrant a different assessment, but that possibility needs utility confirmation. Treat the negative value as a documented screening concern and track the answer, rather than converting it into either a definitive rejection or an assumption that the constraint can be avoided.