i think a big factor is also how you earn your income. if you have a badly paid but regular job and or even if you are unemployed but know that you can't find a job then you can use time when you are not working for other activities. on the other hand if you work as an uber driver or other gig job then every hour on the job counts and you are not going to volunteer time unless you are earning enough so that you feel you can afford it. how much that relates to your income depends on your lifestyle. and that also depends on what you were used to growing up.
i can't think of any volunteering opportunity that only takes an hour unless it is something you can do at home or nearby. otherwise you also have to consider travel times, getting ready, etc. any activity no matter how short usually cost me a full afternoon or evening.
