A CHP plant sized and optimized around its design heat-to-power ratio rarely operates anywhere near that ratio on a random Tuesday in April. Heat demand swings with weather, occupancy, and process schedules, while power demand follows a completely different pattern driven by production shifts and grid pricing. Running a fixed dispatch strategy against two independently moving targets is why so many cogeneration plants leave real efficiency on the table without an obvious single cause to point to. See how iFactory tracks heat-to-power ratio against real-time demand with a Book a Demo.
Two Demand Curves That Almost Never Move Together
Heat and power demand are driven by different variables and rarely peak at the same time. iFactory continuously compares your actual heat-to-power ratio against real-time demand for both, so dispatch decisions reflect current conditions instead of a fixed design-point assumption.
Heat And Power Demand Are Driven By Completely Different Variables
Heat demand tracks ambient temperature, process steam schedules, and building occupancy, none of which have a direct relationship to electrical load. Power demand tracks production shifts, equipment cycles, and in many cases grid price signals that have nothing to do with how much heat a facility needs at that moment. A CHP system designed around one representative heat-to-power ratio is, by definition, mismatched to actual demand most of the time, and the size of that mismatch is exactly what determines how much recoverable efficiency is being left on the table.
Weather-Driven Heat Demand
Ambient temperature swings shift heat demand by large margins day to day, while electrical demand from production equipment stays comparatively stable across the same period.
Shift-Driven Power Demand
Production shift changes and equipment start-up sequences create sharp electrical demand swings that have no corresponding change in the facility's actual heat requirement.
Grid Price Signals
Time-of-use pricing and demand response programs can make it economically attractive to shift power output independent of what the heat side of the plant actually needs.
Four Load Allocation Strategies And When Each One Wins
Most CHP dispatch decisions come down to choosing which demand to prioritize when heat and power needs diverge, and the right choice changes depending on season, energy pricing, and contractual obligations to either the steam host or the grid.
Follow The Thermal Load
Generation is set to match heat demand, with power output as a byproduct, which maximizes thermal efficiency but can produce excess or insufficient power relative to site need.
Follow The Electrical Load
Generation is set to match power demand, with heat recovery as a byproduct, which is common when grid export value or avoided purchase cost dominates the economics.
Base-Load With Peaking Boiler
The CHP unit runs at a steady output sized to the minimum expected demand, with a supplemental boiler covering heat peaks that exceed the base-load thermal output.
Economic Dispatch Optimization
Generation is continuously adjusted based on real-time fuel cost, grid price, and thermal value, aiming to maximize total plant economics rather than following either load alone.
Your CHP Unit Is Optimized For A Ratio It Rarely Hits
iFactory tracks live heat and power demand against your actual dispatch strategy, showing exactly where the mismatch is costing efficiency today.
Using Thermal Storage To Decouple Heat Timing From Power Timing
Thermal storage, typically a hot water or steam accumulator tank, gives a CHP plant the ability to generate heat at one time and use it at another, which is one of the few tools available for genuinely decoupling the timing mismatch between heat and power demand rather than just choosing which one to prioritize at any given moment.
Generate During Power Peaks
Run the CHP unit to match a power demand or grid price peak, storing any excess recovered heat rather than dumping it.
Store Recovered Heat
Charge the thermal storage vessel with excess heat that would otherwise be lost when generation is set to follow the electrical load.
Discharge During Thermal Peaks
Draw stored heat during periods of high thermal demand without needing to increase generation output at that moment.
Reset The Cycle
Return to charging storage during the next favorable generation window, keeping the cycle aligned with whichever demand currently has the higher economic value.
The Right Dispatch Priority Shifts With The Season
A dispatch strategy that performs well in winter can be the wrong strategy in summer, since the underlying heat-to-power ratio the facility actually needs shifts substantially across the year.
| Season | Dominant Demand | Typical Priority |
|---|---|---|
| Winter | Heat (space heating, process steam) | Follow thermal load |
| Shoulder Seasons | Balanced heat and power | Economic dispatch optimization |
| Summer | Power (cooling load, production) | Follow electrical load |
| Peak Grid Price Events | Power (export or avoided purchase value) | Maximize generation, store excess heat |
These priorities are typical defaults rather than fixed rules, since a facility with a strong absorption chiller load in summer can still carry meaningful thermal demand outside the traditional heating season.
Why Spark Spread Alone Doesn't Capture The Full Picture
Spark spread, the difference between electricity value and fuel cost, is a common shorthand for CHP economics, but it undervalues the plant whenever thermal output has real value, such as displacing boiler fuel or supporting a process that can't run without steam. A dispatch decision based on spark spread alone can walk away from generation that is actually profitable once the avoided cost of separately produced heat is properly credited to the calculation.
How Often Dispatch Strategy Should Actually Be Reassessed
Because heat and power demand move on different timescales, a review cadence built around a single frequency misses either the fast-moving signals or the slow seasonal ones.
Where CHP Optimization Programs Fall Short
Plants that struggle to capture the full value of their CHP investment tend to share a handful of recurring gaps in how dispatch decisions are actually made day to day.
Running One Fixed Strategy Year-Round
A strategy that performs well in winter can quietly underperform for months once the seasonal demand balance shifts, if the dispatch priority is never revisited.
Undervaluing Thermal Output
Dispatch decisions based only on spark spread ignore the avoided boiler fuel cost of the heat being produced, undervaluing generation that is actually profitable.
Underusing Thermal Storage
A thermal storage vessel that sits mostly idle wastes the one tool available for decoupling generation timing from heat demand timing.
Reviewing Ratio Only At Contract Renewal
Waiting until a steam host or power purchase agreement renewal to reassess actual heat-to-power demand means years of accumulated mismatch go unaddressed.
What Plants Typically See After Adding Ratio-Aware Dispatch
Plants that move from a fixed dispatch strategy to real-time heat-to-power ratio tracking tend to see the same categories of improvement, with the magnitude depending on how seasonal and variable their original demand profile was.
Frequently Asked Questions
Q: Why does our CHP plant seem less efficient in shoulder seasons than in winter?
Shoulder seasons typically bring heat and power demand closer together in magnitude, which sounds like it should be easier to balance but often actually exposes weaknesses in a dispatch strategy that was tuned for a clearly dominant winter heat load. When neither demand clearly dominates, a fixed follow-thermal or follow-electrical strategy leaves more value on the table than during winter or summer, when one demand type is obviously in charge. Reach out through Support Contact to review how your specific demand profile shifts across the year.
Q: Is thermal storage worth adding if we already have a supplemental boiler for peak heat demand?
A supplemental boiler and thermal storage solve different problems. The boiler adds capacity when total heat demand exceeds what the CHP unit can produce, while thermal storage shifts when CHP-generated heat is actually used, letting the unit run for its best power economics without wasting the associated heat output. The two are often complementary rather than substitutes, with storage reducing how often the supplemental boiler needs to fire and the boiler covering the peaks storage capacity alone cannot fully absorb.
Q: How do we know if we're undervaluing our thermal output in dispatch decisions?
A useful check is comparing dispatch decisions made purely on spark spread against what the decision would have been if the avoided cost of producing that same heat from a standalone boiler were included. If those two calculations frequently disagree, particularly during periods when boiler fuel costs are elevated, that is a strong sign thermal output is being undervalued and generation is being curtailed or dispatched suboptimally as a result. A Book a Demo session can walk through this comparison using your actual cost data.
Q: Does switching dispatch strategy require operator intervention every time conditions change?
It depends on how the dispatch logic is implemented. A manually managed strategy does require an operator or engineer to recognize shifting conditions and adjust priority accordingly, which is realistically only practical on a daily or seasonal basis. An automated economic dispatch approach continuously recalculates the optimal balance based on live fuel cost, power price, and thermal value, removing the need for manual intervention at the real-time level while still allowing operators to set overarching priorities or constraints.
Q: How often should our heat-to-power ratio be reassessed against actual site demand?
Beyond the real-time and daily dispatch adjustments, a seasonal review is generally the right cadence for reassessing which dispatch priority strategy fits current conditions, since demand patterns shift gradually rather than abruptly outside of major operational changes. An annual review comparing the full year's actual heat and power demand against original equipment sizing assumptions is also worth doing, particularly if production levels, building occupancy, or process steam requirements have changed meaningfully since the CHP system was originally designed.
Match Dispatch To Demand, Not To A Design-Day Assumption
iFactory brings live heat demand, power demand, and thermal storage state together so your CHP dispatch strategy adapts to today's conditions automatically.
