What circuit allows you to go more than 15A? I'd be afraid of forgetting how much that draws, and triggering the breaker by accidentally plugging something else into that circuit.
Watt's up, doc?
Input-- 120V x 1.4A = 168 Watts [about four 40W lightbulbs]
Output-- 5V x 21A = 105 Watts
Standard AC outlet: 120V x 15A = 1800 Watts
Most AC plugin devices are limited to 1500W; very few things draw that much, generally only heating/ cooling devices, etc.
I use a 14K BTU portable heat pump in the garage and have only ever seen a peak power draw of ~1450W in heat cycle mode, using a little watt/power meter. With the unit producing about 4.5-5 KW resistance heater equivalent BTUs, it's a fairly efficient source of HVAC [only need heat a few days a year anyway, but cooling near year-around if in the garage].
Cheap either way, only paid about $260 new for it [on sale], for 14,000 BTUs of raw A/C capacity, compare that to a typical small 14K [slightly more than "1 ton"] split central-type system starting around $1,800-2,500 retail, plus installation, for ~$3,000+.
Costs: 53.85 BTU per $1.00, compared to 4.67 BTU per $1.00. Or $0.01857 per BTU, vs. $0.2143 per BTU, ~12 times more expensive for a traditional split system.
A BTU is a BTU, watts is watts, parts is parts...
The 'lectric water heater's getting old, going to replace it with a "hybrid" heatpump one. Cost is more than double, but it's much more efficient [4-5 times], with a payback of about a year on the electric bill, gravy after that. Plus, it exhausts "COLD" into the ambient garage air, how kool is that?