How to Calculate Power-to-Liquid E-Fuel EROI

Power-to-liquid (PtL) projects promise carbon-neutral fuels by combining renewable electricity, captured carbon dioxide, and hydrogen synthesis. Investors, offtakers, and policymakers scrutinise these projects through the lens of energy return on investment (EROI): how much usable chemical energy the fuel delivers relative to the energy consumed in production. Because PtL value chains span electrolysis, reverse water-gas-shift reactors, Fischer–Tropsch synthesis, and distillation, energy accounting can fragment across teams. A transparent, unit-consistent EROI calculation brings everyone back to the same baseline.

This walkthrough assembles the data you need, outlines the conversion factors, and demonstrates how to blend electricity, thermal utilities, and carbon capture energy into a single ratio. Use it alongside cost modelling in the e-methanol cost guide and compliance planning covered in the SAF mandate exposure walkthrough to present one integrated business case.

Launch the PtL EROI calculator

Definition and boundary

EROI is the ratio of useful energy output to total energy input. For PtL pathways, the useful output is typically the lower heating value (LHV) of the finished fuel—jet fuel, diesel, or methanol—per kilogram. Energy inputs encompass all electricity consumed by electrolysers, compressors, synthesis reactors, and auxiliaries, plus thermal energy for reverse water-gas-shift reactors, distillation, and product conditioning. Many analysts also include the energy required to capture, purify, and compress CO₂ feedstock.

Establish a clear system boundary before crunching numbers. Decide whether upstream electricity transmission losses, balance-of-plant HVAC, and storage boil-off fall inside the scope. Align the boundary with financial modelling so EROI, levelised cost, and carbon intensity metrics reference the same mass basis. Misaligned boundaries are a common pitfall when reconciling EROI with policy incentives such as the ones tracked via the clean hydrogen 45V carbon intensity guide.

Variables, units, and measurement sources

Collect a consistent data set for one kilogram of finished fuel. Recommended variables include:

  • Hfuel – Lower heating value of the final product (MJ/kg). Source: fuel specification sheets or laboratory calorimetry.
  • Eelec – Electricity consumption per kilogram (kWh/kg). Source: process simulation, electrolyser vendor data, compressor and pump nameplate ratings.
  • Etherm – Thermal energy inputs (MJ/kg) for reactors, solvent regeneration, or distillation. Source: heat and mass balance calculations.
  • Ecap – CO₂ capture or conditioning energy (MJ/kg). Source: direct air capture models or amine scrubbing datasheets.
  • Eaux – Optional auxiliary loads such as cryogenic storage, inert gas generation, or wastewater treatment (MJ/kg). Include when significant.

Convert all energy quantities to megajoules before aggregating. Electricity often arrives in kilowatt-hours, so multiply by 3.6 MJ/kWh. Track measurement provenance; when you later validate the EROI, stakeholders will want to cross-reference heat balances or supervisory control and data acquisition (SCADA) logs.

Formula derivation

Once the data set is standardised, calculating EROI is straightforward. First convert electricity to megajoules. Then sum all input energies and divide the fuel’s LHV by that total.

Etot = (Eelec × 3.6) + Etherm + Ecap + Eaux

EROI = Hfuel ÷ Etot

Net Energy = Hfuel − Etot

Because PtL processes rarely recapture condensation heat, the lower heating value provides a realistic representation of usable energy. If your downstream equipment recovers latent heat, note the assumption explicitly and apply the higher heating value consistently across numerator and denominator.

Step-by-step workflow

1. Normalise process simulations

Begin with a validated process simulation (Aspen Plus, gPROMS, or an in-house energy balance). Export the electricity and thermal duty per kilogram of fuel. Confirm that electrolyser load factors match your intended operating profile—capacity factors below 50% often increase specific energy consumption due to idle losses.

2. Capture auxiliary loads

Audit support systems such as water purification, nitrogen blanketing, carbon dioxide compression, and product storage refrigeration. These auxiliaries can shift EROI significantly, especially in e-kerosene facilities that require sub-zero storage. Convert each auxiliary load into MJ/kg and append it as Eaux.

3. Quantify capture and conditioning energy

If you supply CO₂ via direct air capture, include the steam and electricity requirements from your capture skid. When using industrial point sources, account for solvent regeneration and compression to pipeline pressure. Many engineering teams underestimate this component; align it with the methodology used in the direct air capture energy guide to maintain consistency.

4. Calculate totals and EROI

Sum the inputs, divide LHV by the total, and report both EROI and the net energy difference. Present the breakdown by component so decision-makers see whether improvements should target electrolysis efficiency, thermal integration, or capture technology.

5. Interpret results for stakeholders

Communicate the ratio with context. EROI values below 1.0 indicate the process consumes more energy than the fuel supplies. That may still be viable if policy credits or carbon pricing reward carbon-neutral molecules, but make the trade-offs explicit. Compare scenarios—baseline, heat integration upgrades, renewable electricity price reductions—to demonstrate sensitivity.

Validation and monitoring

Validate the calculation by cross-checking simulation outputs against commissioning data. Instrument critical equipment with energy meters and log consumption per tonne of product. When operations data diverge from design, update the EROI calculation and record the delta. Many teams embed EROI tracking into their monthly performance dashboards alongside gross-margin analytics derived from the e-methanol calculator.

Monitor the energy mix as well. If you procure grid electricity, track marginal emission factors to ensure the PtL product still meets sustainability targets. Pair EROI trends with carbon intensity metrics so offtakers see both energy efficiency and climate impact improve over time.

Limits and interpretation

EROI is a scalar ratio; it does not reveal temporal dynamics or capital intensity. A design with modest EROI may still win if it uses stranded renewable power or qualifies for production credits. Conversely, a high EROI pathway might fail if it depends on scarce biogenic CO₂ or expensive catalysts. Treat EROI as one dimension of a broader decision matrix that includes cost, carbon intensity, reliability, and policy eligibility.

Also note that process improvements can change system boundaries. For example, integrating waste heat recovery reduces thermal inputs but might increase capital cost and maintenance overhead. When reporting improvements, state whether you adjusted the boundary or added new auxiliary loads so comparisons remain apples-to-apples.

Embed: Power-to-liquid EROI calculator

Enter fuel heating value, electricity, thermal utilities, and capture energy to obtain an immediate EROI ratio and net energy margin in MJ/kg.

Power-to-Liquid E-Fuel EROI Calculator

Benchmark synthetic e-fuel designs by translating electricity, thermal utilities, and CO₂ capture energy into an energy return on investment ratio.

Useful energy released per kilogram of finished e-fuel.
Electricity consumed by electrolysis, synthesis, and auxiliaries for each kilogram of fuel.
Steam or other thermal utilities required. Defaults to 0 when blank.
Additional energy for direct air capture or point-source CO₂ conditioning. Defaults to 0 when blank.

Screening tool. Pair with detailed process simulations before making investment decisions.