Is 1/2 inch Copper Line big enough from 500 Gallon Propane Tank to Cabin

I’m setting up propane at my off-grid cabin and want to sanity-check my line sizing before I finalize things - the 1/2 copper line running from 500 Gallon propane tank to the cabin.

Current setup:
- 500 gal propane tank outside
- approx 80 ft run from tank to cabin
- 1/2" copper line

Inside loads:
- Rinnai RX160iN tankless water heater (~160,000 BTU)
- Gas range (~60,000 BTU total)
So roughly ~220k BTU demand if everything runs at once.

Right now I have these two Regulators:
At tank: red Cavagna-style regulator (appears to be low-pressure ~11" WC, typical single-stage setup)
At cabin: second regulator mounted on exterior wall (appears to be 11" WC / 0.4 PSI second-stage regulator) feeding interior appliances

From what I’m learning, it seems like:
My current setup might be undersized if it’s low-pressure the whole way
A lot of people run a 2-stage system (10 PSI at tank → 11" WC at cabin) to make smaller lines work over distance

Questions for others running similar setups:
- What size line are you running from tank to cabin, and over what distance?
- Anyone using 3/4 inch?
- Anyone using anything else but copper?
- Are you running low pressure the whole way, or a 2-stage system?
- If low pressure, what pipe size did you need to support ~200k+ BTU?
- Any real-world issues with 1/2" line at this distance?
- If you switched to 10 PSI, was it worth it vs upsizing pipe?

Trying to avoid re-running the 1/2 inch copper line if possible, but also want to do it right the first time.

Appreciate any real-world setups or lessons learned.  Thanks!!!

Your distance and the power of gas appliances is greater than what I planned (tiny gas stove to be used in summer only and on demand water heater) and I have used 3/4" pipe after research several years ago.

220k BTU/hour is roughly 6m³/h or 100L/min.
Running that into a pressure drop calculator gives 0.036 bar or 0.53 psi.

Add 0.4 psi you want to keep inside and you get at least 1 psi that needs to come out at the regulator from the tank.
I would probably add a little more for extra margin so the pressure doesn't fluctuate too much.

I have a 330 gallon tank around 80 feet from the house entry, 1/2" copper underground all the way. The regulators and underground piping were installed by the gas company 30-some years ago, and I don't know what the one on the tank is set at; the one by the house is obviously set to standard 11" w.c. It powers the stove and a Polaris water heater which heats the whole house in winter (at least it did until I built my RMH to heat the main floor ).

500 ft is a long run. try this calculator: https://heat-calculator.com/lp-gas-pipe-sizing-calculator.php