First time commuter needs advice
Start with safety.  Wear a good helmet and get some good lights.  Leave a spare charger at work.  

Practice the commute on a Saturday.  Ride in get lunch and ride back.  If you are mobile on Sunday then you are good on Monday.  

If you can leave a car at work and lock your bike safely then you can split some days.
Monday you drive in with the bike and ride the bike home.
Tuesday you ride in and drive home.
Wednesday you drive in and ride home.
Thursday you ride in and drive home.
If you drive in Friday problem you don't have the car for the weekend.
So haul your bike home on Thursday.
On Friday you ride or bike both ways.
This lets you build up. 
In a few months you should be riding both ways. 
If you are totally out of shape then it take a couple months.  

At 7 miles each way you are kind of in a dead zone. 
I am in my 50s but I ride a lot and for me 7 miles is 30 minute sprint and I recover in 10 minutes.
It is perfect as it does not take a lot of time but is a legitimate workout.
Out of shape it is an hour each way and you might not recover by the time you ride home. 
Even for a strong rider more than 15 miles each way starts to become a time management issue. 
But I would rather be on a bike an hour than in car an hour.