As far as I heard in (some of) the universities a person having a tenure track position who fails to get grants may not get tenure.
I am wondering what might be consequences of not getting grants for a tenured professor. (Say may he or she get more teaching load? more administrative load? What will happen if he or she will not agree for that?)
In your answers please indicate about what country are you talking about.
In the US, once you have tenure it is difficult to get fired other than for misconduct and hard even then. But, you don't need to get annual raises or further advances in rank unless you are seen as a contributor. What constitutes contribution depends on the institution. For some, grants are very important. For a few, they outweigh all else, partly because they fund students. But not all institutions are like that. For some, grants are nice but not essential.
But, whatever the mission of the institution, not contributing will leave you in a bit of a dead end with little chance to choose courses or committees, etc.
While it may be possible to have a 30+ year career without doing more than the minimum, you will likely still be earning at the end about what you were at the start.
Moreover, department heads, have subtle ways to punish you, by assigning you things that you won't really like doing. And who knows where your office will be.
In my research university in Sweden, the rules are fairly clear:
There is no (official) angle to "refuse" to do more teaching. "Tenure" in Sweden isn't really tenure in the US sense - it's more akin to being a permanent staff member with certain well-defined freedoms. If you are asked to teach more as per the rules of the department and you refuse, that's a fireable offense (you are not fulfilling your work contract).
There was a case at Northwestern University maybe 20 years ago. A tenured professor, a medical researcher with no teaching duties, was supposed to get research grants which would cover his salary. Then one year it happened that he did not get the grant. So he sued, and argued in court that the university must pay his salary, since he was tenured. But the court did not agree. Yes, he was tenured, so he could not be fired; but his contract with the university did not specify that the university must pay his salary.
In Germany, either doing a traditional habilitation (non-tenure track) or going the Junior-Professorship (tenure track) path, not having acquired any grants where you have been a principal investigator is likely to be a big disadvantage versus competitive applicants for a full professor position. Especially for transitioning from Jun.-Prof. to tenured professor an examination of teaching, publication track and acquired funding is standard now.
There are also funding programs like ERC from european union which allow during funding time to take money to different universities/institudes. So "winning" an ERC grant over 2 millon € will increase significantly your likelihood of being approached by universities/institutes. There is a funding likelihood of around 30% at the German Research Foundation (DFG). Both of above paths often last for 4-6 years, so having not been successful at the DFG or many other numerous funding possibilities doesn't really speak for a candidate. Also it is quite common that you start and help writing funding proposal during your PhD work in Germany.
It is important to note that at german universities not much tenured teaching positions exist and not much tenured research positions apart from professors that therefore are expected to do research their whole job lifetime.
In the U.S., in math, at my R1 university, a tenure-track person who does not have an NSF grant will have a hard time getting tenure, currently. Ironically, it's not that mathematicians truly need money to "do research", since we don't need labs or equipment, really, nor "research assistants" to wash test tubes or do field work. True, funding to go to conferences can be viewed as necessary... "conferences" (=pointless jet-setting around the world...) are an issue in themselves.
The point (in my context) is that somehow the approval, expressed in terms of grant funding, of the NSF, is the purest (!?!) expression of the value of one's research. :)
Ok, perhaps no one really believes this in their heart-of-hearts, but it's an easy sell to other faculty who don't understand the work, to the Dean (most often an engineer, for whom funding is ... forgive me... everything), and to VP's. Within the department, non-grant-funding is an "excellent" excuse to sabotage a tenure vote, freeing up a space for one's own clique.
After tenure, things are not quite so precarious. Still, extra summer salary, and funding for trips to conferences, are things that are useful and attractive. In some places, I'm aware that lack of external grant funding will cause Deans or department heads to assign extra teaching or other punitive things. As though external funding per-se were the ... only? ... goal.
Given all the vagaries of "federal funding", depending on one's frame of mind, one might want to ... at some point... work through/beyond that, and be able to think about one's subject without imagining bureaucrats leaning over one's shoulder, disapproving, etc.
Sadly, it does appear that many idealistic models of "the academy" are ever-less viable.
