At this time getting "quality time" (blech) will be a challenge. Too often it is get home and retreat to your gadgets.
I'd schedule some; the repetition makes it a thing. Being a thing is good these days.
It's meals for me. My son and I eat at the table without gadgets or tv. It's been that way his whole life. I try to keep the food interesting when I can, so it can be a topic to start with.

Remember to enjoy it, my eldest daughter is 14 and I haven't spent time with her in the last 5 years (ex is to blame) but I will and I will cherish every moment

That's great, just take it easy and give her space, remember it's new for both of you.

Just keep it real

(Oh, sorry...you were asking for advice on staying energized.)

1. Car rides are good for heart to heart talks. My oldest girl who is now 16 is quiet at home but car rides usually end up with great talks.

2. If you have any skills like changing a tire or basic home maintenance, show her how to do those things. She may never need them, but if things go wrong, she'll be able to handle things.

3. Cook and bake together. If you don't know how, learn with her. Start basic but learn some more complex things. My kids cook and bake with my ex all the time. It's actually really sweet. They have a great relationship even though we aren't together anymore.

It will get easier when you get a rhythm going. You will surprise yourself.

Listen sincerely. Make time for her.
And caffeine. Lots of caffeine.

Good luck lol

Keep it light. Ensure that there are reasonable boundaries and rules and that they are followed. Ensure that if they are not followed, there are reasonable and consistent consequences, perhaps escalating consequences if a boundary is habitually crossed. Just that will go a LONG way.

Love her. Spend time with her. Let her know she’s important.

Enjoy every minute of it, it won't last forever and it is the best thing you can be doing with your time right now, give it your all.
BTW Girls are harder tthan boys and that is a hard age. Hope you have close female friends you can turn to for advice and support. My ex and I split when my daughter was 8 and my son 7. I have been a single dad since, she is now 33 and he is 31. She got a little difficult at 15.

At 15, she's practically an adult. She shouldn't be too high maintenance.

Cat-naps are truly amazing when you can get away with them.

Plant rose bushes under her windows. Nice big thick ones.

If she tolerates it try to get her to go to movies-if you get tired you can always take a nap-lol.

Maintaining energy was the least of my concerns or problems when my daughter was 15.

Glad you have this opportunity- both of you!