This article by Paul Gilster, 'What Kardashev Really Said," which was sent to me by a few of you, is well worth looking at, for it outlines the various ways in which different people - the present author included - have construed Nikolai Kardashev's classification system of civilization types:
As the article notes, the scheme was used by Carl Sagan and many others, each adapting it and in some cases, deliberately modifying it or, in my own case, developing what I call "corollaries," which we'll get back to. But for Kardashev, the types emerged from his consideration of radio astronomy, and of projects like SETI:
"Kardashev is a radio astronomer and among the pioneers of SETI, and his idea of classifying civilizations according to their ability to harness energy was directly related to his experience in radio telescopy (thus I find myself again in this post verging into the territory of SETI, METI, and Existential Risk). Kardashev asked himself how powerful an extraterrestrial radio signal would have to be in order to be detected, “by conventional radio astronomical techniques.”  The numbers he came up with were quite high, and this furnished the basis of his tripartite division of civilizations into Type I, Type II, and Type III.
"If a civilization could radiate EM spectrum emissions at the energy levels of naturally-occurring astronomical radio sources, such a civilization could be detected as easily as we detect pulsars, radio galaxies, and the like. For a civilization to radiate at such levels of energy, however, would require technological capacities beyond our current abilities...Thus from a Kardashevian perspective, the existential risk of METI is negligible, as only very advanced and powerful civilizations would be able to transmit to the universe at large, while younger, less advanced, and therefore more vulnerable civilizations are restricted to passive listening, for all practical purposes."(Emphasis added)
There are a number of nuances to Kardashev's classification system, which Mr. Gilster points out, including the fact that while many people think that in the scheme of things, we are not yet at a Type I level of civilization (I and many others have made this mistake), in terms of his actual scheme, we are already at the level of Type I civilization,do to the level of our energy consumption. The reason why is Kardashev's actual definition of the three levels:
"Here is Kardashev’s original formulation of the three types of civilizations he recognized:
"I – technological level close to the level presently attained on the earth, with energy consumption at ~4 x 1019 erg/sec.
"II – a civilization capable of harnessing the energy radiated by its own star (for example, the stage of successful construction of a “Dyson sphere”); energy consumption at ~4 x 1033 erg/sec.
"III – a civilization in possession of energy on the scale of its own galaxy, with energy consumption at ~4 x 1044 erg/sec."
Thus, as Mr. Gilster points out, this has led to some confusion over his definitions of levels or Types I and II, and much confusion over the Type Two level exists because Kardashev himself drew attention to the different types of stars themselves:
"Note that there is an ambiguity of the Kardashev metric in terms of actual vs. comparable energy usage. A carefully constructivist account of Kardashev would insist that a Type II civilization is “a civilization capable of harnessing the energy radiated by its own star,” and that all of this energy must in fact come from that particular star and from no other source. In other words, given a strict conception of a Type II civilization, a civilization utilizing energy quantitatively equivalent to but not identical to the actual energy produced by a single star would not constitute a Type II civilization."
Thus, if one defines Type II as the actual use of a star rather than the use of "equivalent energy," one arrives at the ambiguity inherent in the definition of a Level or Type II civilization, for this would depend on the type of star in view: it is a "regular" yellow star of modest size, as our Sun? or a brown dwarf? a red giant?
As Mr. Gilster observes, it was Dr. Michio Kaku who suggested the "corollary" view that the ability to manipulate systems of planetary scale that might be an equally plausible way to classify civilization types:
"Michio Kaku is even more imaginative than Sagan and others in drawing out the implications of Kardashev’s civilization types as he sees them. For example, here is how Kaku defines a Type I civilization:
'Type I civilizations: those that harvest planetary power, utilizing all the sunlight that strikes their planet. They can, perhaps, harness the power of volcanoes, manipulate the weather, control earthquakes, and build cities on the ocean. All planetary power is within their control.'
"Kaku goes into much more detail in Chapter 8, “The Future of Humanity,” in his book Physics of the Future , most of which chapter is an exposition of Kaku’s interpretation and extrapolation of Kardashev civilization types.
"There is something intuitively attractive and plausible about equating a type I civilization with planetary energy resources, a type II civilization with stellar energy resources, and a type III civilization with galactic energy resources, and it would further be intuitively attractive and plausible to equate planetary energy resources with the burning of fossil fuels that are the result of a planetary biosphere (and are not to be derived from stars and are not found in space). This is Kaku’s approach. But this is not what Kardashev said.
"The ideas of Sagan, Kaku and others for a typology of civilizations are worthwhile, but they aren’t what Kardashev said. Nevertheless, as the idea of Kardashev civilization types becomes further elaborated, many writers routinely refer to Kardashev types, but this only compounds the ambiguity because one never knows if they are referring to what Kardashev actually said, or to subsequent embroidering upon what Kardashev said."
Picking up on Kaku's suggestion, that it is the ability to manipulate systems of planetary, stellar, or galactic scale, in my own books I have called them "corollaries" precisely in order to distinguish them from Kardashev's actual views, and I have elaborated these "corollaries" in order to analyze or "reverse engineer" the thought-and policy-forming culture of "the breakaway civilization," in order to see how it would have approached and responded to the problem posed by the UFO and some of its apparently hostile but paradoxically not "immediately threatening" behavior. In Covert Wars and Breakaway Civilizations and Covert Wars and the Clash of Civilizations I have essentially argued that this breakaway group would have concluded that it would be necessary to demonstrate human capability to manipulate systems of planetary scale(weather and so on), and perhaps even our local star, in a kind of "gunboat diplomacy" designed to convince "the others," whoever they may be, that human capability exceeds mere nuclear and thermonuclear weapons, a sort of "interplanetary 'Don't Tread on Me'" banner.
Whatever the value of such an analysis or recasting of Kardashev's system, however, it is worth noting, as Mr. Gilster points out, that Kardashev himself viewed his formulations as tentative, a feature which invites others to "revise and extend" his ideas:
"Kardashev concluded his famous paper with this reflection:
'…we should like to note that the estimates arrived at here are unquestionably of no more than a tentative nature. But all of them bear witness to the fact that, if terrestrial civilization is not a unique phenomenon in the entire universe, then the possibility of establishing contacts with other civilizations by means of present-day radio physics capabilities is entirely realistic.'
"These are the sage words of a scientist who expects (or at least hopes) that others will take up his work and expand upon it. Tentative formulations invite others to revise and extend them, and certainly many have sought to do this with Kardashev’s civilization types. I don’t wish to suggest that the extrapolations and extensions of Kardashev’s idea are illegitimate, only that they aren’t at all what Kardashev said, and we ought to be clear about this."
As indicated above, I think Kardashev's system has merits both as a scheme of classification of any non-human civilizations as might exist, but equally importantly, can perhaps serve as a valuable tool in extrapolating or "reverse engineering" the thought-culture of technocratic elites tasked with formulating analysis and responses to the UFO phenomena since the end of World War Two, and perhaps may even serve as a useful tool for the examination of very ancient structures and ideas in ancient texts.
But howsoever one modifies or revises and extends Kardashev's system, Mr. Gilster is right, few of those modifications actually note their departure from Kardashev's own definitions, and we all stand corrected.
See you on the flip side.