BTU to kWh Converter

Instantaneously translate BTU into kilowatt-hours and see how a BTU/hr-rated appliance converts into daily energy use and cost.

AC / Heater Energy & Cost

Use the appliance power rating, daily hours of use, and your utility rate to see the kWh and cost per day.

How to Use This Calculator

Enter your appliance's BTU/hr power rating, how many hours it runs each day, and the kWh price from your electricity bill. The calculator instantly converts the rate into kilowatts, multiplies by daily runtime to find kWh, and multiplies those kilowatt-hours by the cost per kWh.

The estimates assume a steady load during every hour of operation and standard SI conversions. Adjust inputs to match seasonal changes or different usage patterns.

Methodology

  • Convert the BTU/hr rating into kilowatts by dividing by 3412.14 (or multiplying by 0.000293071039).
  • Multiply the kilowatts by daily runtime to find kilowatt-hours used per day.
  • Multiply the daily kilowatt-hours by your local cost per kWh to get the daily energy bill.

Full original guide (expanded)

Energy Conversion (BTU ← kWh)

Use this mini-converter for pure energy units. It is ideal when you have a total amount of heat (BTU) and want to compare it to energy in kWh.

AC / Heater Energy & Cost Calculator

This is the tool most homeowners need. Enter the appliance’s BTU/hr rating, your daily run time, and the cost per kWh on your bill to estimate the kWh and dollars used each day.

The hero calculator above preserves this logic while keeping all controls and results side-by-side.

The Important Difference: BTU vs. BTU/hr

The biggest point of confusion is between energy and power.

  • BTU (British Thermal Unit) is a unit of energy.
  • BTU/hr (BTU per hour) is a unit of power—the rate at which energy is used.

Your air conditioner is rated in BTU/hr because it describes how much heat it can move each hour. You pay your utility for the energy it consumes over time, measured in kWh.

Formulas Used

1 BTU = 0.000293071039 kWh
1 kWh = 3412.141633 BTU
1 kW = 3412.141633 BTU/hr
1 BTU/hr = 0.000293071039 kW

Combine the conversions with runtime and the rate to see the total cost:

  1. Find Energy: kW × hours = kWh
  2. Find Cost: kWh × cost per kWh = total cost

Frequently Asked Questions (FAQ)

How many kWh does a 10,000 BTU AC use?

A 10,000 BTU AC is rated at 10,000 BTU/hr, which is ~2.93 kW. Multiply the 2.93 kW by how many hours it runs to get the daily kWh.

What is a BTU?

A British Thermal Unit is the energy needed to heat one pound of water by one degree Fahrenheit.

What is a Kilowatt-Hour (kWh)?

A kilowatt-hour is the energy used by running one kilowatt for one hour. Utility companies bill in kWh.

Related Calculators

Formulas

Energy conversion: 1 BTU = 0.000293071039 kWh — 1 kWh = 3412.141633 BTU.

Power conversion: 1 kW = 3412.141633 BTU/hr — 1 BTU/hr = 0.000293071039 kW.

Cost calculation: (BTU/hr × 0.000293071039) × hours = daily kWh; daily kWh × cost per kWh = daily cost.

Citations

NIST — Weights and measures — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/weights-and-measures

NIST — SI units — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/owm/metric-si/si-units

Changelog
  • Version 0.1.0-draft — 2026-01-19: Initial audit spec draft generated from HTML extraction.
  • Reviewed formulas and sources for accuracy.
✓ Verified by Ugo Candido Last Updated: 2026-01-19 Version 0.1.0-draft
Version 1.5.0
+ round2(safe).toFixed(2); } }; function parseInputs() { const parse = (node) => { const parsed = Number.parseFloat(node.value); return Number.isFinite(parsed) ? parsed : NaN; }; return { btuHr: parse(els.btuHrInput), hours: parse(els.hoursInput), costPerKwh: parse(els.costInput) }; } function validate(inputs) { const errors = []; if (!Number.isFinite(inputs.btuHr) || inputs.btuHr <= 0) errors.push('BTU/hr rating must be greater than 0.'); if (!Number.isFinite(inputs.hours) || inputs.hours <= 0) errors.push('Hours per day must be greater than 0.'); if (!Number.isFinite(inputs.costPerKwh) || inputs.costPerKwh < 0) errors.push('Cost per kWh must be 0 or greater.'); return { ok: errors.length === 0, errors }; } function compute(inputs) { const powerKw = inputs.btuHr * BTUHR_TO_KW; const kwhDay = powerKw * inputs.hours; const costDay = kwhDay * inputs.costPerKwh; if (![powerKw, kwhDay, costDay].every(Number.isFinite)) return null; return { powerKw, kwhDay, costDay }; } function format(outputs, inputs) { const kwh = round2(outputs.kwhDay); return { cost: formatCurrency(outputs.costDay), kwhDisplay: kwh.toFixed(2), powerDisplay: round2(outputs.powerKw).toFixed(2), btuDisplay: Number.isFinite(inputs.btuHr) ? inputs.btuHr.toLocaleString('en-US', { maximumFractionDigits: 0 }) : '—' }; } function render(formatted) { els.dailyCostDisplay.textContent = formatted.cost; els.kwhDayDisplay.textContent = `${formatted.kwhDisplay} kWh`; els.kwDisplay.textContent = `${formatted.powerDisplay} kW`; els.btuHrDisplay.textContent = `${formatted.btuDisplay} BTU/hr`; els.costContext.innerHTML = `Based on ${formatted.kwhDisplay} kWh per day.`; } function renderError(errors) { if (!errors || errors.length === 0) { els.errorBox.style.display = 'none'; els.errorBox.textContent = ''; return; } els.errorBox.style.display = 'block'; els.errorBox.textContent = errors.join(' '); } function update() { const inputs = parseInputs(); const validation = validate(inputs); if (!validation.ok) { renderError(validation.errors); return; } renderError([]); const outputs = compute(inputs); if (!outputs) { renderError(['Unable to compute results. Please revise the inputs.']); return; } const formatted = format(outputs, inputs); render(formatted); } function reset() { els.btuHrInput.value = DEFAULTS.btuHr; els.hoursInput.value = DEFAULTS.hours; els.costInput.value = DEFAULTS.costPerKwh; const debouncedUpdate = debounce(update, 100); document.querySelectorAll('#inputsCard input, #inputsCard select, #inputsCard textarea') .forEach((el) => { el.addEventListener('input', debouncedUpdate); el.addEventListener('change', debouncedUpdate); }); update(); } const converterState = { lock: false }; function initEnergyConverter() { const syncFromBtu = () => { if (converterState.lock) return; converterState.lock = true; const value = Number.parseFloat(converterEls.btuInput.value); if (!Number.isFinite(value) || value === 0) { converterEls.kwhInput.value = ''; converterState.lock = false; return; } converterEls.kwhInput.value = (value * BTU_TO_KWH).toFixed(6); converterState.lock = false; }; const syncFromKwh = () => { if (converterState.lock) return; converterState.lock = true; const value = Number.parseFloat(converterEls.kwhInput.value); if (!Number.isFinite(value) || value === 0) { converterEls.btuInput.value = ''; converterState.lock = false; return; } converterEls.btuInput.value = (value * KWH_TO_BTU).toFixed(2); converterState.lock = false; }; converterEls.btuInput.addEventListener('input', syncFromBtu); converterEls.kwhInput.addEventListener('input', syncFromKwh); } Array.from(input.addEventListener('change', debouncedUpdate); }); els.calcBtn.addEventListener('click', update); els.resetBtn.addEventListener('click', reset); initEnergyConverter(); update(); })();