#btu

Swimming-pool and spa heating maths as an API, computed locally and deterministically — the thermodynamics a pool owner, builder or service tech sizes a heater and budgets a heat-up with. The heat-time endpoint gives the hours to warm a body of water: energy = gallons × 8.34 lb/gal × the temperature rise in °F (that many BTU), divided by the heater's BTU/hr output — raising 20,000 gallons by 10 °F is 1,668,000 BTU, about 4.2 hours on a 400,000 BTU/hr gas heater before surface losses. The heater-size endpoint inverts it: the output you need to hit a temperature rise within a target time, so the same job in 24 hours wants only about 69,500 BTU/hr. The heat-pump endpoint gives a heat pump's electricity and cost — kWh = thermal BTU ÷ 3412 ÷ the COP (5–6 for pool units in mild weather) — so that 1,668,000 BTU costs about 89 kWh at a COP of 5.5, a fraction of resistance heat. Pass the temperature rise directly, or a current and target temperature. Everything is computed locally and deterministically, so it is instant and private. Ideal for pool-builder and service apps, heater-sizing and quote tools, spa and hot-tub calculators, and energy-comparison sites. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 compute endpoints. Ideal figures — add for surface and wind losses. For pool chemistry use a pool-chemistry API.

api.oanor.com/poolheat-api

HVAC sizing maths as an API, computed locally and deterministically from standard rule-of-thumb factors. The cooling endpoint estimates the air-conditioner load for a room — in BTU per hour, tons of cooling and kilowatts — from the floor area (in square feet or metres, or length × width) using a baseline of about 20 BTU/h per square foot, with adjustments for the number of occupants, a kitchen, sun exposure and ceiling height. The heating endpoint estimates the heating load from the area and a climate zone (mild through very cold) or a custom BTU per square foot. The convert endpoint converts between BTU per hour, tons of cooling, kilowatts and watts (one ton = 12,000 BTU/h ≈ 3.517 kW). Everything is computed locally and deterministically, so it is instant and private. These are rule-of-thumb estimates in the EnergyStar style — a proper Manual J load calculation accounting for insulation, windows and local climate is recommended for a real installation. Ideal for HVAC and home-improvement tools, air-conditioner and heater sizing guides, smart-home and energy apps, and contractor quoting. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is HVAC sizing; for appliance running cost use an energy-cost API.

api.oanor.com/hvac-api