The value is in reducing the right grid-demand intervals—not simply running a generator for a few summer hours.
Contents
| Assumption or result | Value |
|---|---|
| Reduction at each captured peak | 2,000 kW |
| Avoidable annualized charge | $6/kW-month × 12 months |
| Capture all four monthly peaks | $144,000 gross annual saving |
| Capture three of four equally | $108,000 gross annual saving |
| 40 dispatch hours at $0.18/kWh net incremental cost | $14,400 operating cost |
| All-four contribution before fixed and capital costs | $129,600 |
A few intervals can influence a year of cost
ERCOT’s 4CP measure uses demand during the system’s highest coincident 15-minute interval in each of June, July, August and September. For customers whose transmission-related charges depend on that measure, reducing grid demand in those intervals can have value well beyond the energy saved.
The transmission allocation mechanism is not a universal retail savings rate. Your tariff, retailer agreement and billing treatment determine which charges you can actually avoid. Get the applicable dollars per kW in writing before valuing dispatch.
The challenge is predicting the interval
You know the final peaks after the month closes. During the month, dispatch must cover a set of likely windows. Miss one monthly peak and, with equal reductions, you lose one quarter of the intended 4CP reduction. More conservative dispatch improves coverage but adds fuel, starts and maintenance.
Combine forecast signals with real-time site import, generator availability and a clear dispatch authority. Measure the reduction at the utility boundary; a generator’s terminal output overstates the effect if auxiliaries rise or the site load increases during dispatch.
Use a contribution calculation
The table assumes $6/kW-month of genuinely avoidable cost. The $0.18/kWh input is net incremental dispatch cost after crediting purchased energy that generation replaces. Subtract fixed service contracts, permitting, standby charges, capital recovery and dispatch outside the assumed hours separately. Avoid counting the avoided energy twice.
Try your own assumptions
Illustration only. Enter the avoidable charge from your applicable tariff and retail contract; the $6 default is hypothetical.
Assumes equal reduction at each captured peak, the same MW throughout dispatch, and 12 billed months. Operating cost should be net of avoided purchased energy. Excludes fixed O&M, capital, financing, standby/distribution charges, testing outside dispatch, outages and taxes. No savings are guaranteed.
Reliability is a separate benefit
A generator can also reduce interruption losses, but nameplate capacity alone does not establish backup capability. Protection, transfer scheme, black start, fuel resilience and the critical-load boundary must support the intended operating mode. Price a specific avoided-outage scenario rather than promising that any single outage will pay for the plant.
Check operating permission before selling the savings
Routine economic dispatch may require a non-emergency operating authorization. Do not assume an emergency-engine allowance automatically covers 4CP dispatch. Establish the applicable air permit, interconnection/export rules and dispatch conditions before committing the equipment.