Propane & LPG Tank API

Propane and LPG tank maths as an API, computed locally and deterministically — the usable-fill, energy and burn-time numbers a homeowner, RV-er, grill-master or HVAC tech works out at the tank. The tank endpoint turns a tank size into real numbers: liquid propane is 4.24 lb per gallon and holds 91,452 BTU per gallon (about 21,569 BTU per pound), so a 20 lb barbecue cylinder carries roughly 4.7 gallons and 431,000 BTU. It knows the two ways tanks are sized — a portable cylinder (20, 30, 40 lb) is rated by the propane weight it holds, while a bulk tank (100, 250, 500, 1000 gal) is filled to only 80 % of its water capacity to leave room for expansion, so a 500-gallon tank actually holds 400 gallons of propane and about 36.6 million BTU. The burntime endpoint divides that energy by an appliance’s BTU-per-hour input rating to give run time: that same 20 lb cylinder runs a 30,000 BTU/hr patio heater about 14 hours, and an optional hours-per-day turns it into days. The refill endpoint costs a fill from a price per gallon, gives the cost per 100,000 BTU so you can compare propane to natural gas or electricity, and — with an appliance rating — the running cost per hour. Everything is computed locally and deterministically, so it is instant and private. Ideal for home-energy, HVAC, RV, off-grid, grilling and outdoor-living app developers, fuel-cost and tank-monitor tools, and propane-delivery calculators. Pure local computation — no key, no third-party service, instant. US units. Live, nothing stored. 3 compute endpoints. For vehicle fuel economy or the ideal gas law use a different API.