Are tube watts equal to solid state watts?

I remembered reading sometime back that the power for a tube amp is equivalent to double that in a solid state amp. So for eg. a tube amp with 40watts is equal in power to a solid state amp of 80watts.

Did I remember reading that correctly?

You might remember correctly reading this supposition, but it's incorrect. A watt is a watt. This topic has been discussed here at length. Research the threads for further details.
A watt is a standard unit of measurement. Here's a definition.
I agree that a watt is a watt, but tube amps can play louder due to smoother clipping characteristics than SS amps of similar power, so they will tend to seem more powerful - at least that has been my experience. There was an interesting demo at the Stereophile show in NYC last year comparing a 30 watt tube amp and a 200 watt SS amp, the tube amp seemed just as powerful because the SS amp was noticeably clipping at a certain volume level and it was not noticeable with the smaller tube amp.
I have to add this to the discussion.A while back I run with success,my Aerial 10T,known to be power hungry speakers with a Conrad Johnson MV-55.
A watt is a watt is a watt. Only present day audiophiles would ask this question. Making a distinction without a difference is the territory of subjective audiophiles, but hey these days anything goes!
Agree that the subjective appearance of 'more power' from a tube amp is due to the fact of "soft clipping" (the amplifier when pushed to the limit of maximum power distorts in a friendly way) vs the solid state amp's tendency to sound dreadful when pushed to the limits and it begins to 'clip' the signal off.
Solid state amps could be designed to sound like the tube amp if the manufacture wanted to do so. (but the tradeoffs in non-clipping situations causes most if not all to avoid this.)
Regarding the demonstration of the 30 watt vs the 200 watt amps above, perhaps there's an explanation that would explain the apparent lack of difference.

As a youngster, I remember most of the receivers I owned had power meters (you all remember the 70s, right?). I recall watcthing those meters rarely getting above a couple of watts.

It seems that the speakers would have a tremendous impact on the demo. If the speaker were relatively efficient then they should be able to produce high SPLs using either amp because at no point was either amp pushed to its limits.

If my supposition is correct, then it would be hard to perceive a power differential. I.E., regardless of total capability, consuming a couple of watts from either amp isn't operating at the limits.

The other point I'll offer is that the difference between 30 watts and 200 watts isn't that great. If a doubling of power is required for a perceived difference in loudness (I think that's 3 dB, but could be wrong), then the difference from 30 watts to 200 is around 6-9 dB (I could be way out of my depth here, so please correct my thinking if it's wrong).
I think the issue is not that tube watts are any different in terms of power; the issue is distortion. Watt-for-watt, tube amplifiers (in general) make less of the distortions that the human ear objects to. The result is that with a transistor amplifier you rapidly run into a harshness that stops you from turning up the volume any higher, in avoidance of pain and discomfort. This does not happen as much with tubes and the result of *that* is that a smaller tube amplfier can often be driven to put out more 'comfort' watts than a much larger transistor amplifier can.

IOW there is a greater percent of 'usable' power in a tube amplifier... generally speaking that is.
I don't know about you but I like mine on white bread with mayonnaise, a little mustard, and lettuce.

On the one hand a watt is a watt. There is no way around it.
On the other hand, driving a tube amp into clipping is by far a less unpleasant experience as is the case with solid state amps, where, when they reach their limits, the sound breaks up, gets brittle and harsh. Not so, with well designed tube amps.They still sound musical, when the powermeter - should they have such a thing - are already well in the red.

ah and Vic, white bread is fattening, as is mayonnaise. You should try Pumpernickel!

Oops, I just saw that Elizabeth pointed out the same explanation, no Vic, not your sandwich, the amp thing... Should I erase my post? Nope, as the poet says: "Great minds think alike" (-;
Hlgoh2006, need anymore info? or do you feel your question has been answered?
Those meters on the old school receivers were(with few exceptions) NOT peak reading meters. They only showed average power output. Peak outputs easily exceed 10X the average output for a given listening level.
Kjweisner- For a better understanding of how Watts, DB and perceived loudness relate, read this: (
Thanks for all your responses! Its been enlightening...!
all-tube guitar amplifiers are a good example of two principles- ONE- capturing tonal details that bring out the "woodiness" of the instrument, and TWO- being able to accurately reproduce the wide dynamic range of the instrument- i.e.- going from softly strumming or picking to "digging into the strings"- tube amps have the capability of letting you hear the contrast between soft and loud effortlessly. i started out with an (admittedly inexpensive) 120 WATT stereo solid state amplifier which had alot of excellent features as well as two 12" drivers, but the tone of my les paul seemed a bit flat and totally lacked the body you get from acoustic guitars. i took it back a few days later; the store thankfully allowed me to exchange it for a FENDER TWIN REVERB (all tube-25W/100W switchable). i plugged in my guitar, and as the amp warmed up the most INCREDIBLE SOUNDS came out of the speakers. the amp screamed and cried; it could sound sweet and nice or tear your head off (in a good way!) with anguish and pain. even though i'm only an amateur player, everyone in the store seemed to stop what they were doing to listen to the wonderful sounds coming out of my guitar. i was more than satisfied to say the least. of course the amp had the typical noisy "tube rush"- the solid state amp had no such issues- but i was now a "guitar god" and i could stand next to a mountain and chop it down with the edge of my hand. this was all at the 25 watt setting, too. MY POINT IS, the fender delivered emotion and tonal colors, and sounded "real" when going from soft to loud. the solid state amp sounded alien like the guitar was made out of a "plastic compound" instead of mahagony.
All things being equal,problem they are not since most tube amps are built better with better trannys,tubls sound better and need a lot less power, many very expensive tube amps are only 30watts and they kick ass!! they say tubs rule for a reason, they same reason there are new tuble amp co starting up all the time,Nick
Thanks, Rodman99999 for the reference.