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API · /uvalue-api

U-Value & R-Value API

healthy 4,531 Subscribers

Building-fabric thermal maths — U-value, R-value and heat loss — as an API, computed locally and deterministically. The rvalue endpoint takes a wall, roof or floor build-up as a list of layers (each given as a thickness and a thermal conductivity, or a thickness and a named material from a built-in table, or a direct R-value) and adds the interior and exterior surface resistances to return the total thermal resistance R = Rsi + ΣR_layer + Rse and the thermal transmittance U = 1/R, in both metric (RSI, m²K/W and W/m²K) and imperial (R-value) units, with a per-layer breakdown. The layer endpoint gives the R-value of a single material from its thickness and conductivity, R = thickness/conductivity, and solves for whichever of the three you leave out, with conductivities for concrete, brick, timber, plasterboard, mineral wool, EPS, XPS, PIR and more. The heatloss endpoint computes the steady-state heat loss through an element, Q = U·A·ΔT, in watts, BTU per hour and kWh per day from a U-value (or R-value), an area and a temperature difference (direct or as indoor minus outdoor), and an annual figure from heating degree days. Everything is computed locally and deterministically, so it is instant and private. Ideal for building-energy and retrofit tools, architecture and construction apps, insulation and SAP/Passivhaus calculators, and energy-assessment software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is building-fabric thermal performance; for rule-of-thumb HVAC equipment sizing use an HVAC API.

#u-value #r-value #insulation #building-physics #energy #developer-tools
api.oanor.com/uvalue-api
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Machine-readable spec so AI agents can integrate this API.

/api/uvalue-api/openapi.json
/api/uvalue-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
93 ms
Server probes · 24h
Subscribers
4,531
active
Total calls
36
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 2,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • U-value & R-value for single assemblies
  • Metric & imperial (RSI) units
  • 2 req/s for prototyping
  • Community support
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Starter

€9.00 /month

  • 15,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • Multi-layer wall, roof & floor assemblies
  • Total U-factor + heat-loss output
  • ASHRAE material-conductivity library
  • Email support
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Pro

€24.00 /month

  • 80,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • Surface-resistance & air-gap modelling
  • Batch assembly evaluation
  • Compliance-ready U-value reports
  • Priority support
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Mega

€69.00 /month

  • 400,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • High-volume CAD/BIM & estimator integration
  • Full ASHRAE + custom material catalogues
  • 99.9% uptime SLA
  • Dedicated engineering support
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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.

api.oanor.com/propane-api

Hydropower API

Hydroelectric-power engineering maths as an API, computed locally and deterministically. The power endpoint computes the electrical power a hydro plant generates with P = ρ·g·Q·H·η, from the water flow rate, the net head (the effective drop), the overall turbine-generator efficiency (typically 0.80–0.92) and the water density, returning both the gross power at 100 % efficiency and the net electrical output. The sizing endpoint inverts the relation to size a scheme — given a target power it solves the flow rate needed at a known head, or the head needed at a known flow, Q = P/(ρ·g·H·η). The annual-energy endpoint computes the yearly energy from the rated power and a capacity factor (typically 0.3–0.6 for hydro, accounting for water availability and downtime), E = P × 8760 h × capacity factor, and an optional revenue from an electricity price. Flow is in cubic metres per second, head in metres, efficiency 0–1, power in watts, kilowatts and megawatts. Everything is computed locally and deterministically, so it is instant and private. Ideal for renewable-energy, micro-hydro, civil-engineering, feasibility and sustainability app developers, run-of-river and reservoir tools, and energy education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is hydroelectric generation; for wind-turbine power use a wind-power API, for solar resource a solar API and for pump (energy-consuming) duty a pump API.

api.oanor.com/hydropower-api

Capacitor API

Capacitor maths as an API, computed locally and deterministically. The energy endpoint computes the stored energy and charge of a capacitor from any two of the capacitance, the voltage and the charge — E = ½CV² = ½QV and Q = CV — in joules, millijoules and coulombs. The charging endpoint models the RC charging and discharging transient: the time constant τ = RC, the voltage at a given time, V(t) = Vs(1 − e^(−t/RC)) when charging or V(t) = V₀·e^(−t/RC) when discharging, and the percent charged, or — given a target voltage — the time to reach it; a capacitor reaches about 63 % of the way in one time constant and over 99 % in five. The combination endpoint computes the total capacitance of capacitors in series (1/C = Σ1/Cᵢ) or parallel (C = ΣCᵢ). Capacitance accepts farads or the handy µF/nF/pF units. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, maker, embedded and circuit-design app developers, power-supply and timing tools, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is capacitor maths; for AC reactance and resonance use a resonance API and for LED resistor sizing an LED-resistor API.

api.oanor.com/capacitor-api

Wind Power API

Wind-turbine power maths as an API, computed locally and deterministically. The power endpoint applies the wind-power equation P = ½ · ρ · A · v³ · Cp: from the wind speed, the rotor (given as swept area, diameter or blade length) and an optional air density and power coefficient, it returns the total power in the wind, the Betz maximum (the theoretical 16/27 ≈ 59.3 % limit) and the power actually extracted at the chosen coefficient — in watts, kilowatts, megawatts and horsepower. The energy endpoint multiplies power by time and an optional capacity factor to give the energy produced in watt-, kilowatt- and megawatt-hours, taking the power directly or deriving it from the wind and rotor. The sweptarea endpoint is a geometry helper: swept area from a diameter, radius or blade length, plus the blade-tip speed and tip-speed ratio from an rpm. Wind speed accepts metres per second, km/h, mph or knots; air density defaults to 1.225 kg/m³ at sea level. Because power scales with the cube of wind speed and the square of rotor diameter, small changes move it a lot — the API shows every intermediate value. Everything is computed locally and deterministically, so it is instant and private. Ideal for renewable-energy and engineering tools, education and physics apps, site-assessment and feasibility calculators, and STEM projects. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is wind-turbine power physics; for the Beaufort wind scale use a wind-scale API and for solar arrays use a solar API.

api.oanor.com/windpower-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for U-Value & R-Value API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call U-Value & R-Value API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for U-Value & R-Value API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does U-Value & R-Value API cost?
U-Value & R-Value API has a free tier with 100 calls / month. Paid plans start at €9.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is U-Value & R-Value API GDPR-compliant?
All requests to U-Value & R-Value API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/uvalue-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/uvalue-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/uvalue-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/uvalue-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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