Reserve Margins And Adequacy

Reserve margin is the cushion of firm capacity above peak demand; firm dispatchable resources are what fill it as fossil plants retire.

The planning cushion

A grid keeps a reserve margin, firm capacity above forecast peak demand, so it can absorb an unexpected outage, a demand spike, or a forecast error. Typical target margins are on the order of a tenth to a fifth above peak. The margin must be met with resources that count at the peak, which is capacity value, not average energy.

As coal and older gas retire, the firm capacity that filled reserve margins leaves the system. Replacing it with variable renewables alone erodes the margin, because their capacity credit is low. Firm dispatchable additions like the burner (MetroVolt) are designed to backfill this reserve.

Firmness, not energy, fills the margin

A megawatt-hour of surplus solar at noon does nothing for a reserve margin measured at the winter evening peak. Only firm capacity that is available at that peak contributes. This is the crux of why grids adding renewables still procure firm resources.

Honest gate

MetroVolt's contribution to a reserve margin equals its firm capacity, which is limited by its availability (0.86 to 0.995, design-stage) and best realized across a redundant fleet rather than a single unit. The contribution is real in principle and unproven in hardware.