Is anyone seriously using prefixes above Giga, besides for counting bytes or boasting numbers in popular science articles?
In physics, in practice you either state the number in exponential notation and don't care abut it or for brevity introduce a more appropriate unit: barns (10⁻²⁸ m²) and electronvolts (10⁻¹⁹ J) in nuclear physics or solar mass (~10³⁰ kg) in astrophysics, etc.
Electricity production for a country is reasonable measured in TWh, and I think I've seen this in newspapers discussing energy/gas in Europe.
But from Wikipedia:
> In the United Kingdom ... Demand for electricity in 2014 was 34.42 GW on average (301.7 TWh over the year) coming from a total electricity generation of 335.0 TWh.
We aren't there yet for power:
> The synchronous grid of Continental Europe is the largest synchronous electrical grid (by connected power) in the world. ... In 2009, 667 GW of production capacity was connected to the grid
Boasting in popular science articles with large prefixes is hardly better communication compared to scientific notation. If the prefixes aren't commonly used (anything above tera/peta really isn't), then the majority of people have no frame of reference for what it is any more than it being "a big number".
In physics, in practice you either state the number in exponential notation and don't care abut it or for brevity introduce a more appropriate unit: barns (10⁻²⁸ m²) and electronvolts (10⁻¹⁹ J) in nuclear physics or solar mass (~10³⁰ kg) in astrophysics, etc.