Drawing No. EH–ES–010 // Environmental & Safety Engineering

Electricity LCA Methodology and System Boundaries

Reviewed August 2026

A fair comparison begins before any number is calculated: define the question, functional unit, boundary, technology, geography, time period, allocation and impact-assessment method.

Framework ISO 14040/14044Default functional unit 1 MWh deliveredBoundary Cradle-to-graveApplication Electricity generation

Comparison rule: two published values are not automatically comparable just because both are labelled “life-cycle.” Their functional units, boundaries, technology variants and characterization methods must align.

The four connected phases of LCA

ISO 14040 framework

1 · Goal & scopePurpose, audience, functional unit, system boundary and comparison requirements.

2 · InventoryEnergy, materials, emissions, water, land and waste flows for processes inside the boundary.

3 · Impact assessmentClassify inventory flows and apply characterization factors to impact categories.

4 · InterpretationCheck completeness, sensitivity, uncertainty and conclusions against the original goal.

IterationData gaps or sensitivity results can require revising assumptions and repeating earlier phases.

ISO 14040 describes the principles and framework, while ISO 14044 specifies requirements and guidelines for conducting and reporting the study [1][2]. The phases are iterative rather than a one-way calculation sequence.

Functional unit: what service is being compared?

Use energy, not nameplate capacity

Recommended electricity basis

1 MWh of net electricity delivered to the grid

This compares the service supplied by different technologies. It includes auxiliary consumption when net generation is used and can include delivery losses if the boundary says so.

Common invalid comparison

1 MW installed capacity

A megawatt is power, not energy. Plants with different capacity factors, lifetimes and degradation can deliver very different lifetime electricity from the same installed MW.

Lifetime electricity = P_net × CF × 8,760 × L × (1 − λ)
P_net = net capacity · CF = lifetime capacity factor · L = operating life · λ = delivery-loss fraction

Cradle-to-grave electricity boundary

Declare every included stage

Raw materialsMining, extraction, processing and production of fuels and construction materials.

ManufacturingFuel conversion, enrichment or fabrication; modules, turbines, foundations and balance of plant.

ConstructionSite work, civil structures, transport, installation and commissioning.

OperationFuel use, maintenance, replacements, cooling, auxiliary power and routine emissions.

End of lifeDecommissioning, dismantling, waste treatment, recycling credits and final disposal assumptions.

A plant-level boundary does not automatically include additional transmission, balancing, curtailment, storage or backup capacity. Those belong to a broader electricity-system study. The Energy Mix Model addresses hourly operation and reliability, while the LCA Comparison Tool compares generation technologies within the UNECE boundary.

Why lifetime and capacity factor cannot rescale every impact equally

Separate fixed and generation-dependent stages

I_c = (I_{construction,c} + I_{replacement,c} + I_{end-of-life,c}) / E_lifetime + I_fuel,c + I_operation,c

Construction and end-of-life burdens are largely fixed for a defined plant and are divided by lifetime electricity. Fuel-cycle and operating burdens usually scale more closely with generation. Therefore, changing capacity factor or lifetime should be applied to stage-resolved data—not by multiplying an entire published LCA result by one ratio.

Minimum conditions for a defensible comparison

Check before ranking

Decision	What must be aligned or disclosed	Why it changes results
Functional unit	Net or gross kWh/MWh; plant gate or delivered electricity	Defines the service and denominator.
System boundary	Construction, fuel cycle, operation, replacements, end of life, grid effects	Omitted stages can shift burdens outside the comparison.
Technology variant	Coal PC or IGCC; NGCC; CCS capture rate; PV chemistry and mounting; hydro type	Family labels conceal materially different systems.
Operating assumptions	Lifetime, capacity factor, degradation, outages and auxiliary load	Changes lifetime generation and stage allocation.
Geography and time	Manufacturing mix, fuel source, climate, resource quality and reference year	Supply chains and operating conditions vary regionally and evolve.
Allocation	Co-products, recycling, recovered heat and multi-output systems	Determines how shared burdens or credits are distributed.
LCIA method	ILCD, Environmental Footprint, ReCiPe, TRACI or another named method/version	Characterization models and units can differ.
Uncertainty	Parameter ranges, data quality, model choices and scenario uncertainty	Small numerical differences may not support a clear ranking.

Allocation, recycling and co-products

Method choices with real consequences

Multi-output systems

Combined heat and power, desalination or other co-products require a rule for dividing burdens. Physical relationships, energy or exergy allocation, economic allocation and system expansion can produce different results.

Recycling and end-of-life credits

Results depend on whether recycled content, avoided primary production and future recoverability are assigned to the current or subsequent product system. The rule must be stated consistently.

Uncertainty and sensitivity

A central value is not the full result

Parameter uncertaintyFuel use, material quantities, emissions, lifetime and capacity factor.

Scenario uncertaintyTechnology design, future electricity mix, recycling and end-of-life pathway.

Model uncertaintyCharacterization factors, fate/exposure models and allocation method.

Data qualityAge, geography, representativeness, completeness and verification status.

Sensitivity analysisChange influential assumptions individually and report whether conclusions persist.

Comparative reviewPublic comparative assertions may require stronger documentation and critical review.

Electricity LCA reading checklist

Eight questions before using a published number

Scope and denominator

What decision is the study intended to support?
Is the result per net kWh/MWh, gross generation or installed capacity?
Does “delivered” include transmission losses?
Which lifecycle stages are included?

Comparability and evidence

Is the technology configuration explicit?
What geography, reference year, lifetime and capacity factor are used?
Which LCIA method and version characterize the inventory?
Are uncertainty, sensitivity, allocation and corrections documented?

Frequently asked questions

Five methodology checks

What functional unit should electricity LCA use?

A common functional unit is 1 kWh or 1 MWh of net electricity delivered to the grid. Delivered electricity is different from installed capacity or gross generation.

What does cradle-to-grave mean for electricity generation?

It normally includes raw-material extraction, component and fuel production, construction, operation and maintenance, replacements, decommissioning and waste treatment within the declared boundary.

Why does capacity factor affect electricity LCA results?

Construction and end-of-life impacts are spread across lifetime electricity generation. A lower capacity factor produces fewer MWh over which those fixed impacts can be allocated.

Can results from different LCA methods be compared directly?

Not reliably. Results should use compatible functional units, boundaries, technology definitions, inventory assumptions and characterization methods.

Does generation LCA include storage and grid balancing?

Usually not unless the study explicitly defines an electricity-system boundary. Plant-level generation results should not be treated as complete delivered-system impacts.

References

Primary framework and application sources

Interconnected EngineerHub resources

Reviewed 27 August 2026 · Framework: ISO 14040/14044 · Electricity application: UNECE 2022