Table 1 Challenges and indicators found through a systematic literature review are categorized into four challenges, seventeen sub-challenges, and fifty-three indicators

Social (C₁)

Public engagement (SC₁)

Share of zero-emission vehicles in newly registered passenger cars-% (I₁)

GHG emissions per capita- kg CO₂eq person⁻¹ (I₂)

GHG intensity of power & heat generation- t CO₂eq MillionEUR⁻¹ (I₃)

Average CO₂ emissions of new passenger cars- g CO₂ km⁻¹ (I₄)

Public awareness (SC₂)

The general advancement of knowledge: R&D financed from General University Funds (GUF)- Million Euro (I₅)

The general advancement of knowledge: R&D financed from other sources than GUF- Million Euro (I₆)

Public resistance (SC₃)

Share of renewable energy in gross final energy consumption-% (I₇)

Renewable energy share in transport (RES-T)-% (I₈)

Renewable electricity share (RES-E)-% (I₉)

Renewable energy for heating & cooling (RES-H&C)-% (I₁₀)

Fossil fuel avoidance by renewable energy-% (I₁₁)

Energy justice (SC₄)

Energy affordability-% (I₁₂)

Harmonised Index of Consumer prices-% (I₁₃)

Inability to keep home adequately warm-% (I₁₄)

Household electricity prices- EUR kWh⁻¹ (I₁₅)

Household gas prices- EUR kWh⁻¹ (I₁₆)

Labor transition (SC₅)

Total employment in renewables- employed persons (1000) (I₁₇)

Energy security (SC₆)

Aggregate supplier concentration index (from extra-EEA suppliers)- (0–1000) (I₁₈)

Net import dependency-% (I₁₉)

N-1 rule for gas infrastructure-% (I₂₀)

Electricity interconnection-% (I₂₁)

Market concentration index - power generation- (0–10,000) (I₂₂)

Market concentration index - wholesale gas supply- (0–10,000) (I₂₃)

Available energy, energy supply, and final energy consumption per capita-Kilograms of oil equivalent (KGOE) per capita (I₂₄)

Economic (C₂)

Investment (SC₇)

Companies producing at least 5% of the net electricity generation- Number (I₂₅)

Companies with at least 5% of the electricity generation-% (I₂₆)

Companies with at least 5% of the electricity capacity-% (I₂₇)

Electricity retailers- Number (I₂₈)

Gross domestic product at market prices- Million Euro (I₂₉)

Mitigation and adaptation costs (SC₈)

GHG avoided emissions due to renewable energy-% vs. 2005 (2005 = 0.0%) (I₃₀)

GHG emissions reductions (the base year 1990)-(0–100) (I₃₁)

GHG Intensity of Energy [kg CO₂ eq. toe⁻¹] (I₃₂)

GHG intensity of the economy- t CO₂eq MillionEUR⁻¹ (I₃₃)

Energy productivity- Euro per kilogram of oil equivalent (KGOE) (I₃₄)

Subsidies (SC₉)

Fossil Fuel Subsidies- USD (I₃₅)

Total environmental taxes USD (I₃₆)

Environmental (C₃)

Land use (SC₁₀)

Land Use- Square kilometer (I₃₇)

Land cover- Square kilometer (I₃₈)

Pollutions (SC₁₁)

Landfill rate of waste excluding major mineral wastes-% (I₃₉)

Resource consumption (SC₁₂)

Raw material consumption (RMC)- Thousand tonnes (I₄₀)

Institutional and technical (C₄)

Short-termism (SC₁₃)

Imports of electricity and derived heat by partner country- Gigawatt-hour (I₄₁)

Imports of natural gas by partner country- Million cubic meters (I₄₂)

Imports of oil and petroleum products by partner country Million cubic meters (I₄₃)

Imports of solid fossil fuels by partner country Million cubic meters (I₄₄)

Innovative policies (SC₁₄)

Patent on ENV technologies- Patents per million habitants (I₄₅)

Patents on Energy Union priorities- Patents per million habitants (I₄₆)

Reformations (SC₁₅)

Environmental policies- Number (I₄₇)

Lack of standards (SC₁₆)

Total government budget allocations for R&D- Million Euro (I₄₈)

Lack of infrastructure (SC₁₇)

Transport, telecommunication, and other infrastructures- Million Euro (I₄₉)

New electricity capacity connected- Megawatt (I₅₀)

Gross electricity production-Hydro- Gigawatt-hour (I₅₁)

Gross electricity production-Wind- Gigawatt-hour (I₅₂)

Gross electricity production - Gigawatt-hour (I₅₃)