I'm trying to get a few opinions as I have had 1 electrician tell me i need a subpanel but his whole reason was so i could expand in the future and he didn't really listen to what I wanted. I have had another tell me no I can run a direct burial cable from my main breaker on a single 20 amp circuit to the livestock shed to power the light, 1 outlet for a water pump/heater and 1 outlet for a electric fence controller but I wouldn't be able to expand by much more. Given I only need these specific items, i'm looking at a total of 25 watt pump, 500 water heater, 1.6 joule output for electric fence, 60 watt lightbulb I believe I can do it all on a single 20 amp circuit as I'm sitting at less than 600 watts (assuming I converted the Joules correctly) which is nowhere close to 20 amps
90 feet is the distance from the current panel to the shed.
Best Answer
You state in your comment that you plan to run conduit.
In that case, do NOT use UF cable. Use THWN wiring - the conduit protects it, and it's much easier to pull than UF cable. It may also cost you less, and it can indeed be easily upgraded if or when you or a later owner wants to upgrade.
12Ga should be fine for your planned use. If your use increased, pulling one more wire and changing the feed breaker to a two-pole 20A GFCI breaker and making the circuit an MWBC would double your available power at the building.