Beyond Coal vs. Renewables —Part 3: Emission Avoidance Factor — A New Way to Evaluate Energy Resources

Most energy discussions evaluate power plants based on their own emissions factors.

But electricity systems do not operate in isolation.

What matters is not only how much a resource emits.

What matters is how much it reduces—or increases—the emissions of the overall grid.

This can be measured using a simple concept:

Emission Avoidance Factor (EAF)

EAF can be defined as:

Grid Carbon Intensity – Resource Emissions Factor

If the result is positive, the resource reduces system-wide emissions.

If the result is negative, the resource increases system-wide emissions.

This approach focuses on relative carbon reduction rather than absolute emissions.

Consider the following example.

Suppose the grid carbon intensity at a particular hour is:

0.60 kg-CO₂/kWh

A high-efficiency LNG power plant emits:

0.30 kg-CO₂/kWh

The Emission Avoidance Factor becomes:

0.60 – 0.30 = +0.30

This means the LNG plant reduces overall system emissions by approximately 0.30 kg-CO₂/kWh relative to the existing grid.

Now consider a different situation.

Suppose the grid carbon intensity falls to:

0.20 kg-CO₂/kWh

The same LNG plant still emits:

0.30 kg-CO₂/kWh

The Emission Avoidance Factor becomes:

0.20 – 0.30 = –0.10

In this case, introducing the LNG plant would increase overall system emissions.

The same power plant creates positive value in one hour and negative value in another.

Time matters.

Now consider renewable energy.

Suppose solar generation has an operational emissions factor of:

0.00 kg-CO₂/kWh

If the grid carbon intensity is:

0.20 kg-CO₂/kWh

Then:

0.20 – 0.00 = +0.20

Solar reduces emissions by 0.20 kg-CO₂/kWh.

However, compare that with the earlier LNG example:

Grid intensity = 0.60

LNG emissions factor = 0.30

EAF = +0.30

In this specific comparison, the LNG plant delivers a larger marginal carbon reduction than the solar resource.

This may sound counterintuitive.

But it highlights an important reality.

The value of an energy resource depends not only on what it is.

It also depends on when and where it operates.

A low-carbon thermal plant may sometimes provide greater marginal carbon reduction than a renewable generator operating during a period when the grid is already relatively clean.

This does not mean thermal generation is preferable to renewables.

Rather, it demonstrates that electricity systems should be evaluated dynamically rather than through static technology labels.

Combining hourly matching with grid carbon intensity analysis allows policymakers to identify the highest-value opportunities for emissions reduction.

Instead of asking:

"Which technology is best?"

We can ask:

"Which resource creates the greatest carbon reduction at this specific hour and location?"

That is a much more useful question for designing practical pathways toward decarbonization, affordability, and energy security.

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