I have excel on the pc I use it for maintenance logs. Power not a big deal I only turn it on when I need it and shut it down. Lucky if it sees 4 hours runtime a month.
A dedicated garage PC for 4 hours of usage per month? This is
exactly what I would try to avoid. That is a massive waste of money.
At least with the Beelink, it would be easy to unplug it and carry it back inside (they're compact and lightweight). Assuming your garage already has the monitor, keyboard, and mouse, you'd just need a standard 12V AC adaptor for the Beelink (if you don't want to schlepp that along). That way you could still use it elsewhere in the house the other 726 hours of the month rather than just accumulate dust.
As for tablets, I'm not saying you
have to use an iPad, you are free to use some cheap Android tablet as well. I assume Excel will run on those just fine, as Excel runs fine on iPads; you never mentioned that in your original post. Apple also has their own free spreadsheet application called Numbers with has decent Excel compatibility for mundane spreadsheet functions. And there are cloud spreadsheets (Google comes to mind). There's also Zoho -- a longtime software company -- that also has office productivity tools.
Like I said, I have plenty of other uses for my iPad elsewhere. But it's great for things like document reading, watching videos. And yes, you can even connect mice and keyboards these days to them.
Tablets are sometimes the better solution depending on the situation. Occasionally I find myself needing to refer to a recipe or a video while cooking or baking in the kitchen. In this case, my iPad is way better than my notebook PC because I can easily wipe off the iPad display. No worrying about wet hands, flour, oil, etc. whereas I'd worry more about that with a notebook PC's keyboard. Not sure what you are doing in your garage but if it gets your hands dirty and cleanup is not convenient, a tablet might be a better device. I assume you aren't writing 10 paragraph work e-mails or multi-page customer contracts out there.
And weirdly you selected a particular Beelink model that's
more expensive than the aforementioned Dell model. No real savings there.
To buy a dedicated PC for 4 hours of month isn't how I would allocate my tech budget. Here in 2025, almost anything will let you read PDFs, watch videos, and edit spreadsheets, it's not like you need a specialized device for those tasks. Heck, my ten-year old iPod touch 6th generation can do all of that. And so can a $100 Raspberry Pi 4 running Raspbian (Linux).
You are better off pondering if the device you plan to purchase has other uses the other 726 hours of the month rather than fixating on the archaic paradigm of a dedicated desktop PC for this situation.