How strainful is Super Saiyan?

[GSM123]

When Goku and Gohan leave the Rosat, everybody comments on how natural they feel, and Tenshinhan says this:

However, Super Saiyan being a strainful form was never shown to be the case. Goku isn't shown tiring against Freeza and Vegeta constantly stays as a Super Saiyan throughout the Android Arc, what's stupid if Super Saiyan consumes so much energy. Is this a retcon or what?

 

[Evil Vegeta]

I think the Super Saiyan strain is one of those things that was never clearly established in the story. We know there's a noticeable amount if the minimization of it is considered a big deal from Vegeta. That doesn't really tell us how much of a strain the form has, though. The instability and restlessness of the form seems like more of an annoyance since Goku mentioned those.

 

[Pyro]

Grade 2 was also said to have considerable strain, but Vegeta was doing a dandy job with it.

 

[Captain Cadaver]

Tenshithands' statement is likely only in reference to a base form comparison, which makes sense considering how much training Goku did with Ki control prior to going SSJ and Ten doesn't have reference on the Kaioken to work with. Super Saiyan would have some strain, as it'd be ridiculous for a transformation over twice the Ki output of the highest Kaioken level to not have some tension on the body, though it's significantly less so than it's higher forms.

 

[Ultimate Cell]

Yeah Grade 3 was shown to be strainful as shit but Grade 2 never really gave me the impression of it being strainful.

 

[Flame]

How strainful? We don't really get much of an indication, but as weak and inexperienced as they were it'd be like using Super Saiyan 3 but a little bit easier.