Not sure if its the same for powerlifting,
but a friend of mine who plays a team sport at national level had to nominate which gym he trains at, and nominate one hour slot per day and nominate where they'd be.
Eg if they nominate 9am-10am and at home and they're not home they fail the test. So its good to nominate a time when you're definitely at a particular place, to avoid failure. So early in the morning works best as you're definitely home then, even if it is inconvenient. They can also turn up at the gym you nominate.