We put in an L6-30 outlet.
Without question 240V is the way to go so see if you have a laundry drier outlet in or close to your garage.
BUT! There's a solution that's way faster than the normal trickle charge 110V that you get from the stock Nissan charger, and a dedicated 240V solution, and you might already have it in your garage.
You might also ask an electrician if the existing wiring in a 110V outlet might be suitable for a single 20A plug. You might get lucky. That's a cheap change: just change the outlet. But ask a professional.
This is what you are looking for:
That funny looking hole on the left with the horizontal slot denotes a 20A 110V circuit.
In short, this will give you about 40% faster charging than a normal 110V 15A circuit. The Leaf 'wastes' about 300W per hour during charging so it's a much smaller percentage wasted on 20A vs 15A.
I recommend using evseupgrade.com to upgrade your stock Leaf EVSE, or get an extra here from our Leaf Store on Amazon if you want one to carry around. (Thank you, your Amazon purchase supports us.)
They will set you up with a 20A 110V adapter so you can use 240V and 110V with any amperage up to 20A by modifying your stock EVSE.
I had this done and it is NICE.
Later, you can get 240V added to your garage since the EVSE is already set up for that. This allows you to upgrade in stages, vs. laying all the money out at once.
Ultimately you will want to charge as fast as possible to minimize the hours spent wasting that 300 watts per hour.
Math: 6 hours a day on 110V = 1.8Kwhr wasted. (6x.3Kw). Around here that's about 18 cents.
But let's say you charge 30 days out of the month, then it's $5.40 per month or almost $65 per year.
If you spend $600 on putting in 240V (not unreasonable for the EVSE upgrade and a short wiring run and socket) then saving $65 per year is over a 10% return on your investment.
Cutting your charge time using a 20A 110V will still save you 40% of .3 kwhr so .12 kwhr or 1.2 cents per hour. But if the outlet is already there, it's free money.
If you carry the EVSE around, there are a lot more 20A 110V circuits on buildings than you think. I have been adding them on Plugshare.com.
Using those should add about 7 miles per hour of charge vs 4-5 on the stock EVSE.
Final thought: Since I have BOTH outlets in my garage, and a measured 122V/244V voltage, I can run 6.8Kwhr of power to two cars: 1.95Kwhr and 5.85Kwhr assuming 80% current on both circuits.
At my average useage on my Leaf, the 122V circuit will give me 7.75 hours of range per hour of charge. That should be plenty for almost anyone. 8 hours (probably easily done overnight) would be 62 miles of range. If you plug in at let's say 7pm and charge until 6AM the next day, that would almost fill any Leaf from a totally empty battery which is probably rarely the case. For me, that would be 85 miles of range.
So if you have TWO electric cars, you can still get great useability out of both without the fuss of adding another 240V circuit.
I hope this helped you save some money and increased the usability of your Leaf.