Nuances of comparable

Solution 1:

You are not going to get a quantitative definition of comparable.

Comparable has so many nuances that it can be anything you want it to be, and anything your reader reads into it. In your sentence

It is not expected that the power-effectiveness will equal the effectiveness of dedicated hardware, but it is hoped that it can be comparable

Replace "....it is hoped that it can be comparable" with an unambiguous, quantitative statement.

In one of your comments, you say: "The power consumption of my design is within 2.5 times the power consumption of the dedicated module.... "within" because it varies with frequency, 2.5x is the worst case."

Thus, I suggest: "The power consumption of my design varies with frequency, and, at worst, is 2.5 times the power consumption of dedicated hardware."

You have summarized concisely and without ambiguity. Forget "comparable" and "order of magnitude", which you are going to have to explain later anyway.

Edit in response to Hida's comments about expectations

I suggest that you present your expectations in terms of "acceptable", rather than "comparable". You decided to build this piece of equipment instead of buying it because...why? It was cheaper? Possibly by building it yourself you improved some key aspect of its performance at the expense of other aspects you didn't care about? If so, try something like: "The equipment that I build was much less expensive than off-the-shelf equipment would have been; it [did whatever it did] as well as (better than? nearly as good as ?) the commercial product would have, although with an increase in power consumption, which could be held to an acceptable level."

You are going to explain all this quantitatively later. Acceptable conveys the message that you had quantitative criteria, which you met. Comparable doesn't have that connotation, to me, anyway. You define what is acceptable; anyone can define what is comparable.

Solution 2:

There seem to be two crucial points to consider. 1. Even if 2.5 is the max increase of consumption, the more informative value is the expected new value (understandably, it may be unknown). 2. Who the audience is, and consequently, how precise (or vague) you need to be.

I believe "within the same order of magnitude" is actually one of the more flattering ways of putting things, if it can be expected that the new values will be mostly about double of the original ones. The reason is simple -- if consumption increases twice, then only half of all the possible values will be within the same order of magnitude (in decimal, of course). If the increase is more than double, then a statement about the same order of magnitude is not even true.

Comparable or proportional are vague, placating, and (in their strict sense) vacuously true terms that may perhaps be considered if there is no risk of alienating the audience by being vague, or if the power consumption is a side issue, etc.

Added: The above was written understanding order of magnitude as described here (i.e., as equivalence, where each class is given by the exponent of 10 in the scientific notation of that number). Apparently though, that is not the prevailing meaning of that notion; many interpret it as a relative notion, cf. John Baez quoted in the Wikipedia entry.

Solution 3:

I would posit that that this is an answer dependent on your target audience.

There are two kinds of target audiences (generally speaking) Professional, and Layperson. For my purposes, Professionals are people with detailed knowledge of the subject under discussion, and Laypersons are not. They may be Professionals in other spaces but they lack depth of knowledge and breadth experience on the subject relevant to the writing. For both, comparable means that there is a notable difference relevant to their knowledge. For example, with your module:

Would a Professional [above definition] find cause for pause when deciding to purchase your module over the dedicated module due to it's power consumption? Would they have to modify other parts of a project including your module due to these increased power requirements? If so, it is not comparable.

Would a Layperson even notice? If not, it is comparable.