The Baseline: Human Energy Needs
Before examining modern energy consumption, we should consider the baseline: how much energy does a human body actually need?
The answer is approximately 7 MJ per day (about 2,000 kcal), assuming moderate activity. This represents the absolute minimum energy throughput required for human survival.
In pre-industrial societies, additional energy came primarily from biomass (wood, animal dung) and animal labor. The total energy consumption per capita was perhaps 20-30 MJ per day.
In contrast, modern industrialized societies consume vastly more energy per capita—not because humans have become more wasteful, but because energy enables every aspect of modern life: transportation, heating, cooling, manufacturing, agriculture, healthcare, communications, and countless other services.
Austria as a Case Study
Austria provides an instructive case study for several reasons:
- It is a prosperous EU member state with a high standard of living
- It has good renewable resources (especially hydropower)
- Detailed energy statistics are publicly available
- Its energy mix is representative of central European nations
In 2020, Austria’s total primary energy supply was approximately 1,381 PJ (petajoules), or about 384 TWh.
Energy Supply by Source
| Source | PJ | Percentage |
|---|---|---|
| Oil | 465 | 33.7% |
| Natural Gas | 306 | 22.2% |
| Coal | 94 | 6.8% |
| Biofuels/Waste | 257 | 18.6% |
| Electricity (imports) | 18 | 1.3% |
| Hydro | 151 | 10.9% |
| Wind/Solar/Other | 90 | 6.5% |
| Total | 1,381 | 100% |
Fossil fuels (oil + gas + coal) account for 62.7% of total primary energy supply.
From Primary Energy to Useful Energy
Not all primary energy reaches end users as useful energy. Conversion losses occur at every step:
- Power plant thermal efficiency: 30-60%
- Transmission and distribution losses: 5-10%
- End-use device efficiency: varies widely
Of Austria’s 1,381 PJ primary energy, only about 470 PJ (34%) reaches consumers as useful energy. The rest is lost in conversion.
Final Energy Consumption by Sector
| Sector | PJ | Percentage |
|---|---|---|
| Industry | 317 | 28.5% |
| Transport | 361 | 32.5% |
| Households | 283 | 25.4% |
| Services | 127 | 11.4% |
| Agriculture | 24 | 2.2% |
| Total | 1,112 | 100% |
The Substitution Challenge
If Austria were to completely eliminate fossil fuels, it would need to substitute approximately 865 PJ of fossil primary energy with carbon-free alternatives.
However, because renewable electricity and hydrogen have different conversion efficiencies than fossil fuels, the actual requirement depends on the end use:
Transport: Currently consumes ~361 PJ, mostly as petroleum fuels with ~20% tank-to-wheel efficiency. Electric vehicles achieve ~85% efficiency, so the same mobility could be provided with much less primary energy.
Heating: Currently uses significant amounts of natural gas and oil. Heat pumps can deliver 3-4 units of heat per unit of electricity, dramatically reducing primary energy needs.
Industry: Some industrial heat and chemical feedstocks are harder to substitute. High-temperature processes may require hydrogen or synthetic fuels.
A First-Order Estimate
Taking conversion efficiencies into account, Austria would need approximately 166 TWh of carbon-free electricity to substitute all fossil fuel uses—assuming optimal pathways for each sector.
This compares to current Austrian electricity generation of about 70 TWh, of which 60-70% comes from hydropower.
Decarbonization requires roughly doubling or tripling Austria’s total electricity generation capacity, depending on the technologies deployed.
Per Capita Perspective
Austria’s population is about 9 million. Current total energy consumption is thus:
- 153 MJ per person per day (total primary energy)
- 52 MJ per person per day (useful energy)
Compare this to the 7 MJ per day baseline for human metabolism. Modern Austrians consume about 7 times more useful energy than their bodies require—and this ratio is even higher in countries like the United States.
This additional energy is not a luxury; it represents:
- Heated and cooled buildings
- Personal and freight transport
- Food production and processing
- Healthcare and education infrastructure
- Communications and information technology
- Manufacturing and construction
The Path Forward
The numbers presented here are not meant to discourage action. On the contrary, they show that with proper planning and investment, decarbonization is technically feasible.
But the scale of the challenge must be understood. This is not a matter of incremental adjustments or “green” tweaks to business as usual. It requires a fundamental restructuring of our energy system over several decades.
In the next installment, we examine the most promising pathway for decarbonizing transport: electrification.
Data sources: Statistics Austria, International Energy Agency, Austrian Environment Agency