A step-by-step guide to the metric that measures gas-fired power profitability. Learn the formula, who uses it, and how to interpret positive and negative spreads — with interactive tools you can play with.
The spark spread answers a simple question: How much money does a gas-fired plant make (or lose) on each megawatt-hour it produces? It is the gap between what you earn from selling power and what you spend on the gas needed to make that power.
The term comes from the ignition step in a gas turbine — the spark that turns fuel into electricity. A positive spread means gross margin before operations, maintenance, and other costs. A negative spread means the plant would lose money on fuel alone.
Power revenue — what you get from selling 1 MWh of electricity
Fuel cost — what you pay for the gas to produce that 1 MWh
Spark spread = Power revenue − Fuel cost
Three building blocks matter: power price (in $/MWh), gas price (in $/MMBtu), and heat rate (in MMBtu/MWh — how much gas per megawatt-hour). Power and gas use different units, so heat rate bridges them.
First convert gas cost to $/MWh by multiplying gas price × heat rate. Then subtract that from the power price. The result is your spark spread in $/MWh.
Example: Power $50/MWh, gas $5/MMBtu, heat rate 7 → Fuel = 5×7 = $35/MWh → Spread = 50−35 = $15/MWh
Heat rate tells you how much gas is needed to generate one megawatt-hour of electricity. Lower is better: a plant with 7 MMBtu/MWh is more efficient than one with 10 MMBtu/MWh. Think of it as fuel economy for power plants.
Modern combined-cycle gas turbines (CCGT) often run around 7 MMBtu/MWh — roughly 50% efficiency. Older peaker or simple-cycle units may need 9–10+ MMBtu/MWh. The heat rate you use should match the plant you care about.
Lower heat rate = less fuel per MWh = lower fuel cost = higher spark spread (all else equal)
Adjust the inputs below and watch fuel cost and spark spread update in real time. Experiment with high gas prices, low power prices, or different heat rates to see how the spread behaves. A negative spread turns red.
Real markets swing daily. Traders and generators use tools like this (often inside ETRMs) to size opportunities and hedge positions.
A positive spark spread means power price exceeds fuel cost — the plant earns gross margin on each MWh. Generators may choose to run when the spread is positive. A negative spread means fuel costs more than power revenue; running would lose money on fuel before any other costs.
The gauge below reflects the spread: green to the right of zero, red to the left. It is driven by the same inputs as the calculator above (they stay in sync when you scroll).
Generators rely on it to decide when to dispatch gas plants and to structure hedges (e.g. sell power forward, buy gas). Traders trade the spread as a single product — power minus gas × heat rate — on exchanges and OTC markets. Analysts use it to compare profitability across regions and over time.
Each group cares about the same number for different reasons: operations, risk, or strategy.
Beyond dispatch, the spark spread appears in tolling deals (a counterparty pays to use your plant; you earn the spread), spread trading (trading power and gas together to capture the margin), and valuation (how much is a gas plant worth given expected spreads?).
ETRMs and trading platforms often embed spark spread calculators and curves to support deal structuring and risk reporting.
The plant owner provides capacity; the counterparty supplies gas and takes power. The owner earns the spark spread (or a share of it) as a capacity payment.
The spark spread is a simplified benchmark, not a full plant P&L. It ignores operations and maintenance, capital costs, transmission, emissions allowances, and taxes. It also assumes a fixed heat rate; in reality, efficiency shifts with load and ambient conditions.
Use it as a first-pass margin indicator. For investment or contract decisions, layer in the rest of the cost stack.
To move from spark spread to total margin, subtract the other variable costs that apply per MWh: O&M (operations and maintenance), capacity or toll fees (if you pay for capacity or use someone else’s plant), and transmission (delivery to market). Indicative ranges below are $/MWh — actuals vary by region and plant.
If total margin = spark spread − O&M − toll/capacity − transmission is negative, the plant loses money at the margin even though the spark spread might be positive. In that case you would not run: the gross fuel margin does not cover the rest of the cost stack.
A positive spark spread suggests the plant can earn margin on fuel — but dispatch decisions depend on unit commitment constraints. A plant that is currently off faces start-up costs (fuel and wear to bring the unit online), minimum run times (once on, it may have to stay on for several hours), and ramp rates (how fast output can change).
If the spread is only slightly positive and short-lived, the margin over the next few hours may not cover the start-up and no-load cost (fuel consumed at minimum output with no or low sales). So even when spark spread > 0, the plant may not start — the spread is too small to justify committing the unit. Operators and traders use optimization and heuristics that include these constraints.
Dispatch and unit commitment models (e.g. in ETRMs or grid optimization) incorporate these to decide whether to start, run, or shut down.