(1) KNU Definition

Energy density (kWh per dollar of GDP) measures how much energy an economy needs to create value and is essentially the “fuel efficiency” of economic growth. It is crucial for long-term forecasting because future energy demand equals GDP multiplied by energy density, so small errors in its decline rate lead to huge mistakes in required energy supply, infrastructure, and emissions over a century. Sustained reductions in energy density are therefore the key lever that makes economic growth, climate targets, and geopolitical resilience simultaneously achievable.
The KNU, for each zone, is a timeline : a function that tells the decline of energy density from 2010 (or 1980) to 2100.

(2) What the slider in  G2WS does ?

The default value of this KNU has been calibrated for each of the five blocks (once more, without inflation). Working in constant dollars provides more stable results, but also shows that progress is slow (see below)

The slider appplies a correction to the default KNUs. You can see the effect of the correction with the associated KPI, that is the CAGR of density from A to B 

(3) References

You may also ask your favorite LLM (such as Opus 4.5 or GPT 5.2) to make your opinion.

References to web data sources may be found in this page.