This page is based on three papers: Petrakopoulou & García-Tenorio Corcuera (2022), “Introducing the total efficiency to address challenges of the 21st century”, Journal of Cleaner Production 374, 133409, Petrakopoulou & García-Tenorio (2023), “Evaluating hydrogen-based electricity generation using the concept of total efficiency”, Energy Conversion and Management 293, 117438, and García-Tenorio Corcuera & Petrakopoulou (2025), “Evaluating the impact of CO₂ capture and storage on total efficiency: A lifecycle analysis”, Cleaner Engineering and Technology 27, 101002.
Efficiency tells us how much of a fuel's energy a power plant turns into electricity. It is the number we use to compare power plants, set targets and write energy policy.
But efficiency only starts counting when the fuel arrives at the plant. Before that, gas and coal have to be extracted, cleaned, often liquefied, and carried for thousands of kilometres by pipeline, train and ship. Hydrogen first has to be made. All of this uses energy too, and most of it comes from more fossil fuel.
Total efficiency adds that journey to the calculation, together with what happens after the plant, such as capturing and storing CO₂, so that energy sources can be compared on fair terms.
On paper, fossil-fuel power plants look far more efficient than renewable ones. Typical values reported in the literature:
This comparison is not fair. Sun and wind are used where they arrive. Fossil fuels must be found, extracted, processed and shipped before a power plant can burn them, and conventional efficiency ignores every one of those steps. The same is true for hydrogen, which does not exist freely in nature and has to be produced first.
As Europe switches from coal to imported gas, and plans for hydrogen, these hidden steps are getting longer and more energy-hungry. A fair measure has to include them.
Total efficiency keeps the familiar definition of efficiency and adds one term to the bottom of the fraction: the energy spent to make the fuel ready for use.
Diesel in mining machines and trucks, heavy fuel oil in ships, gas burned to run a liquefaction plant. These are counted directly as extra fuel.
Pumps, compressors, conveyor belts and electric trains use electricity. The method traces it back to the fuel burned to generate it, taking into account each country's power mix.
The energy data for each step come from published life cycle assessment studies. Because several studies report different values for the same step, the analysis runs many combinations and reports a range.
Two real power plants in Spain, two long supply chains. Drag the fuel along its route and watch what each step costs.
Hydrogen burns without CO₂, which makes it a candidate fuel for future power plants. But it has to be produced, compressed or liquefied, and transported. The second study applied total efficiency to hydrogen in two existing gas power plants, one in Spain and one in Germany, assuming they switch to hydrogen.
Hydrogen is labelled by colour according to how it is made. Pick a colour and a country.
Values for hydrogen delivered by pipeline, read from the study's result charts and rounded. Delivering by truck instead changes them by less than 1.5 percentage points. Grey, turquoise and yellow hydrogen in the Spanish case use natural gas imported as liquefied gas from Egypt; in the German case the gas is piped from Norway.
Carbon capture and storage (CCS) removes most of the CO₂ from a power plant's exhaust and stores it underground. It is an important option for cutting emissions from gas and coal plants. But it is not free in energy terms: the chemical solvent that captures the CO₂ has to be heated to release it again, and the CO₂ then has to be compressed, piped away and injected.
The third study added these steps to total efficiency, for a gas plant and a coal plant in the UK and in Australia, with fuel from nearby fields and mines.
Results of the study at 85% and 100% capture; values in between are interpolated. Efficiency drops are relative to the plant's own efficiency without CO₂ capture.
Fossil, renewable and hydrogen-based electricity can be compared on the same basis, including everything it takes to bring the fuel to the plant.
Total efficiency shows which steps cost the most, such as long-distance shipping or liquefying gas, and where shorter supply chains or local production would help most.
It shows the full energy price of capturing CO₂, which helps target improvements such as better solvents, heat recovery and shorter transport routes.
It shows that hydrogen made from surplus renewable electricity close to where it is used keeps most of its value, while hydrogen made from imported gas or grid power loses most of it.