When discussing renewable energy on social media it never takes long for negative comments to arrive. One comment I get frequently is from people who share a chart showing global primary energy demand over the last 200 years. They say: ‘Look at the vast amount of fossil fuels we use. We will never be able to replace them with renewable energy. Look how tiny their contribution is.’

The suggestion is that we will need to replace all primary energy with renewable energy and that would be impossible. Because of that, we should just accept that we need fossil fuels forever!

I tend to differ. Here’s why.

Simply put, we don’t need to replace all of the energy inputs into the energy system as long as we can deliver the same services more efficiently. The commentators showing primary consumption graphs have fallen for the ‘primary energy fallacy’, a term coined by the Canadian energy expert and commentator Paul Martin. This fallacy arises when comparing energy sources based on their primary energy consumption, often overlooking fundamental differences in efficiency and utility.

What is the primary energy fallacy?
Primary energy refers to the total energy content of natural resources before any conversion processes, such as coal, oil or renewable electricity. The fallacy occurs when people equate high primary energy inputs with energy services. Measuring energy systems purely on primary energy inflates the perceived contribution of fossil fuels, while underestimating renewables’ efficiency and untapped efficiency potentials through electrification.

The Sankey diagram in Fig 1 shows the UK energy system. All of the energy on the left-hand side is paid for, as Rick Wheatley from consulting firm S7 points out. But consumers are only interested in the energy service they get (see the dark grey box in the bottom right corner). What this Sankey diagram shows very nicely is the huge amount of waste heat produced by the current energy system (see ‘rejected energy’ in light grey box in top right corner).

Fig 1: Dr Rosenow suggests that Sankey diagrams of energy flow are open to reinterpretation – he explains how, using this Sankey diagram of UK energy flow (2017)
Source: Lawrence Livermore National Laboratory
 

This Sankey diagram is now a few years out of date and several things have changed: The most significant change is that, according to Ember data, coal is no longer used for power generation in the UK, and the share of gas generation has declined. On the other hand, we see an increase in renewable electricity generation, in particular wind. Low-carbon renewable sources – wind, solar and hydropower – reached a record high, generating 37% of UK electricity (103 TWh) in 2024, overtaking fossil fuels (97 TWh, 35%) for the first time. This reduces the losses associated with fossil fuel electricity generation.

Another change since the diagram has been created is the increase in uptake of electric vehicles (EVs) and heat pumps. But so far the share of EVs remains low. As of December 2024, the UK had over 1.36 million fully electric cars on its roads, according to Zapmap figures, accounting for approximately 4% of the total 34 million cars in the country. The share of homes with heat pumps is still low with around 1% of UK homes having a heat pump installed.

Measuring energy systems purely on primary energy inflates the perceived contribution of fossil fuels, while underestimating renewables’ efficiency and untapped efficiency potentials through electrification.
 

Why do we waste more than two thirds of the energy inputs? 
One reason is to do with the technologies used. In conventional fossil fuel systems, significant amounts of primary energy are lost as waste heat during combustion. For example, a gas-fired power station only converts 50% on average of the gas burned into electricity, according to government figures. By contrast, renewable systems like wind and solar produce electricity directly.

The second reason is that historically fossil fuels have been cheap, whereas renewables have been more expensive – although that has changed fundamentally. Infrastructure has been developed that delivers the energy services people want without having to pay too much attention to the efficiency of the system. During energy crises these inefficiencies come back and bite us – most evidently during the recent spikes in fossil fuel prices experienced in 2022, following the Russian invasion of Ukraine.

Comparing apples with apples
It is sometimes argued that the solar and wind energy not captured by renewables should also be counted towards primary energy inputs. But that approach is not how energy statistics are typically produced.

For electricity derived from non-combustible sources, the International Energy Agency follows the guidelines set by the Recommendations for Energy Statistics, and employs the physical ‘energy balance method’.

This method ensures a consistent approach across all such energy sources (oil, coal, natural gas, renewables). The primary energy equivalent is determined at the first point in the production chain where multiple energy uses are feasible.

In practice, this means that for sources like hydropower, wind and solar, the primary energy is quantified as the amount of electricity produced at the generation stage. The kinetic energy of moving water or wind, while scientifically a form of energy, is not included in the ‘energy balance’ statistics. Instead, only the electricity output is treated as an energy product in these calculations. This distinction aligns the statistical treatment of non-combustible energy sources with their practical energy contributions.

Also, to be consistent with the proposal of counting all the solar and wind energy not converted by renewable energy technologies, one would need to apply the same approach to fossil fuels. For example, according to a scientific paper published by Science Direct, only up to 6% of solar energy is converted into biomass (by photosynthesis), which in turn is converted into fossil fuels.

Electrification and efficiency
On the energy demand side, the primary energy fallacy fails to recognise the inefficiency of existing technologies and the potential for dramatic improvements. Electrification of energy utilisation currently served by combusting fossil fuels is often significantly more efficient, offering the same energy service for less energy input.

Take EVs for example. They are about three times more efficient than internal combustion engine (ICE) vehicles. Meanwhile, heat pumps can provide the same amount of heat using electricity to harvest pre-existing ambient or waste heat, but with three to five times less energy input than a fossil fuel boiler.

Professor Nick Eyre at Oxford University ran a fascinating thought experiment. What if the world were to electrify industry, buildings and transport to their full potential? What the analysis shows is that just by electrification alone the world would use 40% less final energy. This is a huge efficiency improvement.

So, if the primary energy fallacy is so obviously misleading why are people falling for it and where does it come from?

The roots of the fallacy
Historically, primary energy metrics were developed in the context of fossil fuels, where the focus was on extraction, combustion and thermal efficiency. As renewable energy technologies matured, this outdated approach persisted in energy accounting frameworks. In the European Union, the reliance on primary energy metrics has led to flawed renewable energy metrics and hindered electrification efforts in sectors like heating and transport, as analysis by the Regulatory Assistance Project has shown.

The primary energy fallacy also gets perpetuated because it suits those who are critical of the energy transition. For the uninformed, the argument that we cannot possibly replace the vast amount of fossil fuel we currently use with clean energy seems compelling at first glance. The good news is that we don’t have to.

Implications for energy policy
The primary energy fallacy has practical consequences. Policies designed to reduce primary energy consumption may inadvertently discourage investments in renewables or electrification technologies.

Energy efficiency is a good example. Many energy efficiency policies have been based on primary energy savings targets and incentivised technologies that reduce primary energy consumption. But in the worst-case scenario, such policies can lock-in marginally more efficient fossil fuel infrastructure at a time when the world needs to speed up electrification and the direct use of renewable energy.

In the buildings sector, for example, significant progress has been achieved through improving heating efficiency, such as promoting condensing boilers in the UK. However, many countries still support fossil fuel heating under energy efficiency policies, which risks delaying the transition to zero-carbon alternatives like heat pumps.

In the transport sector, energy efficiency standards have historically improved ICE vehicle performance. With electrification, battery electric vehicles (BEVs) – which are three times more efficient than ICE vehicles – are emerging as the future standard. However, continued efficiency standards for BEVs are essential to minimise electricity demand.

In industry, decarbonising processes will require electrification or carbon capture. Incremental fossil fuel efficiency gains are insufficient unless paired with other zero-carbon solutions.

Policymakers should prioritise replacing fossil fuel technologies with efficient, zero-carbon alternatives instead of marginally more efficient fossil fuel technologies to avoid lock-in, stranded investments and missed decarbonisation targets.

Professor Nick Eyre and I have written a paper on how to reform energy efficiency policy to move away from this approach. We make a number of suggestions for how to reinvent energy efficiency, including focusing programmes and policies more on electrification and targeting energy savings in location and time.

By 2050, global energy-related emissions from fossil fuel combustion must approach zero. This poses challenges for traditional energy efficiency programmes, which often focus on improving fossil fuel combustion processes.

The way forward
The primary energy fallacy represents a critical hurdle in the energy transition, perpetuating outdated paradigms that favour fossil fuels. Addressing this fallacy requires a shift in both mindset and policy tools, ensuring that energy metrics reflect efficiency, sustainability and carbon reduction. By embracing these changes, energy systems can align more effectively with the demands of a zero-carbon future.

In the future, we need to move away from primary energy-based assessments towards metrics that prioritise system efficiency and emissions reductions. By focusing on the carbon intensity of energy systems and the actual energy delivered to end-users, policymakers can better align their goals with the realities of a renewable-powered future.

The views and opinions expressed in this article are strictly those of the author only and are not necessarily given or endorsed by or on behalf of the Energy Institute.

• Further reading: ‘Feeding our energy-hungry world’. Our appetite for energy continues to grow, and with it consumption of fossil fuels and in carbon emissions, but also an increase in renewable sources of energy.
• As the International Energy Agency has clearly stated, we need to double the rate of energy efficiency progress and triple total renewable power capacity by 2030. Today, energy efficiency is the single largest measure the world can take to reduce energy demand, and can provide around one-third of all emission reductions, writes Alan Baird, Country Manager, UK and Ireland, Danfoss.