Electronvolt to British Thermal Unit Converter
Convert electronvolts to BTUs with our free online energy converter.
Quick Answer
1 Electronvolt = 1.518564e-22 BTUs
Formula: Electronvolt × conversion factor = British Thermal Unit
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Electronvolt to British Thermal Unit Calculator
How to Use the Electronvolt to British Thermal Unit Calculator:
- Enter the value you want to convert in the 'From' field (Electronvolt).
- The converted value in British Thermal Unit will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Energy category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Electronvolt to British Thermal Unit: Step-by-Step Guide
Converting Electronvolt to British Thermal Unit involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
BTU = eV × 1.51856e-22Example Calculation:
1 eV = 1.518564e-22 BTU
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
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Need to convert to other energy units?
View all Energy conversions →What is a Electronvolt and a British Thermal Unit?
The electronvolt (symbol: eV) is a unit of energy defined as the amount of kinetic energy gained (or lost) by a single electron when it moves through an electric potential difference of exactly one volt in vacuum.
Fundamental Definition
Mathematical Expression:
1 eV = e × 1 V
Where:
- e = elementary charge = 1.602176634 × 10⁻¹⁹ coulombs (exact, since 2019 SI redefinition)
- V = volt (SI unit of electric potential)
Since 1 volt = 1 joule per coulomb (J/C), we have:
1 eV = (1.602176634 × 10⁻¹⁹ C) × (1 J/C) = 1.602176634 × 10⁻¹⁹ J
This value is now exact by definition following the 2019 SI redefinition.
Physical Interpretation
Imagine a single electron starting at rest:
- Place electron at negative terminal of a 1-volt battery
- Let electron accelerate to the positive terminal through the electric field
- Kinetic energy gained by the electron = 1 electronvolt
The electron's final velocity would be approximately 593 km/s (ignoring relativistic effects), with kinetic energy:
KE = ½mv² = 1 eV = 1.602 × 10⁻¹⁹ J
Common Prefixes and Multiples
Standard SI Prefixes:
- meV (millielectronvolt) = 10⁻³ eV = 1.602 × 10⁻²² J (thermal energies, superconducting gaps)
- eV (electronvolt) = 1.602 × 10⁻¹⁹ J (atomic physics, visible light)
- keV (kiloelectronvolt) = 10³ eV = 1.602 × 10⁻¹⁶ J (X-rays, inner electrons)
- MeV (megaelectronvolt) = 10⁶ eV = 1.602 × 10⁻¹³ J (nuclear physics, gamma rays)
- GeV (gigaelectronvolt) = 10⁹ eV = 1.602 × 10⁻¹⁰ J (particle accelerators, rest masses)
- TeV (teraelectronvolt) = 10¹² eV = 1.602 × 10⁻⁷ J (LHC, highest-energy physics)
- PeV (petaelectronvolt) = 10¹⁵ eV = 0.1602 J (cosmic rays, ultra-high-energy astrophysics)
Electronvolt as Unit of Mass (E=mc²)
Through Einstein's mass-energy equivalence E = mc², the electronvolt can express mass:
Mass Unit: eV/c² (electronvolt divided by speed of light squared)
Conversion:
1 eV/c² = 1.782661921 × 10⁻³⁶ kg
Examples:
- Electron mass: me = 510.9989 keV/c² = 9.109 × 10⁻³¹ kg
- Proton mass: mp = 938.2720 MeV/c² = 1.673 × 10⁻²⁷ kg
- Neutron mass: mn = 939.5654 MeV/c² = 1.675 × 10⁻²⁷ kg
- Higgs boson mass: mH ≈ 125 GeV/c² (discovered 2012, CERN LHC)
Particle physicists routinely express masses in MeV/c² or GeV/c², often abbreviated to just MeV or GeV when context is clear.
The British Thermal Unit (symbol: BTU or Btu) is a unit of energy defined as the amount of heat required to raise the temperature of exactly one pound-mass of water by one degree Fahrenheit, measured at or near water's maximum density temperature (approximately 39.2°F or 4°C).
Official Definition (IT BTU)
The International Table BTU (IT BTU) is the standard BTU used in modern applications:
1 BTU (IT) = 1,055.05585262 joules (exactly)
This definition, established through international steam table conventions, provides an exact conversion to SI units.
Historical BTU Variants
Historically, several BTU definitions existed based on different water temperature ranges:
- 39°F BTU: Using water at its maximum density point (39.2°F) = 1,059.67 J
- 60°F BTU: Using water at 60°F (common in British engineering) = 1,054.68 J
- Mean BTU: Average over range 32-212°F = 1,055.87 J
- Thermochemical BTU: Based on thermochemical calorie = 1,054.35 J
- IT BTU (International Table): Modern standard = 1,055.05585262 J (exact)
Modern Usage: The IT BTU is now universal in US engineering, HVAC, and energy applications unless otherwise specified.
BTU vs. BTU/h (Power vs. Energy)
Critical Distinction:
- BTU = unit of ENERGY (total heat)
- BTU/h (BTU per hour) = unit of POWER (rate of energy transfer)
Example:
- A furnace rated at 80,000 BTU/h delivers 80,000 BTU of heat per hour
- Running for 3 hours delivers 240,000 BTU total energy
- This is analogous to watts (power) vs. watt-hours (energy)
Common Notation:
- BTU/h, BTU/hr, BTUh, Btu/h, or BTUH all mean BTU per hour (power)
- HVAC equipment ratings almost always use BTU/h despite sometimes omitting "/h"
Relationship to Other Units
Energy:
- 1 BTU = 1,055.06 joules (J)
- 1 BTU = 1.05506 kilojoules (kJ)
- 1 BTU = 0.293071 watt-hours (Wh)
- 1 BTU = 0.000293071 kilowatt-hours (kWh)
- 1 BTU = 0.251996 kilocalories (kcal)
- 1 BTU = 251.996 calories (thermochemical)
Power (BTU/h to watts):
- 1 BTU/h = 0.293071 watts (W)
- 1,000 BTU/h = 293.071 W ≈ 0.293 kW
- 12,000 BTU/h = 3,516.85 W ≈ 3.52 kW (1 ton AC)
Note: The Electronvolt is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The British Thermal Unit belongs to the imperial/US customary system.
History of the Electronvolt and British Thermal Unit
The electronvolt's development parallels the history of atomic and nuclear physics in the early 20th century.
Pre-History: Early Electron Research (1897-1920s)
1897: J.J. Thomson discovers the electron using cathode ray tubes, observing electrons accelerated through electric potentials of hundreds of volts.
1909-1913: Robert Millikan's oil drop experiment precisely measures the elementary charge: e ≈ 1.6 × 10⁻¹⁹ C.
1913: Niels Bohr's model of the hydrogen atom calculates ionization energy as 13.6 eV (though he expressed it in ergs or joules).
1920s: Early atomic spectroscopy and quantum mechanics developments naturally worked with energies on the eV scale, though researchers still used CGS units (ergs) or SI joules.
Formalization (1930s-1940s)
Early 1930s: The term "electronvolt" begins appearing in physics literature as particle accelerators (cyclotrons, Van de Graaff generators) accelerate particles through kilovolt and megavolt potentials.
Key Motivation:
- Expressing X-ray energies: 10-100 keV far more intuitive than 10⁻¹⁵ to 10⁻¹⁴ J
- Nuclear reaction energies: Alpha particles with 5 MeV vs. 8 × 10⁻¹³ J
- Particle accelerator beam energies: 1 MeV proton beam vs. 1.6 × 10⁻¹³ J
1932: Carl Anderson discovers the positron (antimatter electron) in cosmic rays, with energies described in MeV.
1930s-1940s: Manhattan Project and nuclear weapons research standardized MeV for nuclear fission and fusion energies.
Post-War Standardization (1950s-1960s)
1948: 9th CGPM (General Conference on Weights and Measures) defines the ampere, indirectly fixing the volt and thus the electronvolt's joule equivalent.
1950s-1960s: Particle physics accelerators (synchrotrons, bevatrons) reach GeV energies:
- Brookhaven Cosmotron (1952): 3 GeV
- Berkeley Bevatron (1954): 6 GeV (first antiproton production)
- CERN Proton Synchrotron (1959): 28 GeV
Standard Practice: By the 1960s, eV/keV/MeV/GeV were universally adopted in atomic, nuclear, and particle physics.
Modern Era (1970s-Present)
1970s-1980s: TeV-scale energies anticipated and achieved:
- Fermilab Tevatron (1983): 1.96 TeV proton-antiproton collisions
2008-Present: CERN Large Hadron Collider (LHC):
- Design energy: 14 TeV (7 TeV per beam)
- Higgs boson discovery (2012): 125 GeV/c² mass
- Current: 13.6 TeV collision energy (2022-2025 Run 3)
2019 SI Redefinition:
- Elementary charge e defined exactly: 1.602176634 × 10⁻¹⁹ C
- Makes 1 eV = 1.602176634 × 10⁻¹⁹ J exact by definition
- Electronvolt recognized in SI Brochure as accepted non-SI unit
Beyond Accelerators:
- Semiconductor physics: Band gaps measured in eV (Si: 1.1 eV, GaN: 3.4 eV)
- Photovoltaics: Solar cell efficiency tied to band gap energies (1.1-1.7 eV optimal)
- Astronomy: Cosmic ray energies up to 10²⁰ eV (Oh-My-God particle, 1991)
The BTU's 170-year history reflects the evolution of thermodynamics, industrial engineering, and American energy infrastructure.
Industrial Revolution Origins (1840s-1860s)
The Problem: Mid-19th century British engineers needed standardized measurements to:
- Compare coal qualities and heating values
- Calculate steam engine efficiency
- Design boilers and heating systems
- Establish fuel pricing based on energy content
Imperial Unit Framework: Early thermodynamics (Joule, Kelvin, Rankine) used British imperial units:
- Pounds (mass)
- Fahrenheit (temperature)
- Foot-pounds (mechanical work)
BTU Development (1850s): The "British thermal unit" emerged as the heat equivalent to raising one pound of water by one degree Fahrenheit, providing an intuitive unit for British engineers familiar with imperial measurements.
Early Usage:
- Coal industry: BTU per pound for fuel quality
- Steam power: BTU input vs. mechanical work output (efficiency)
- Industrial heating: Boiler and furnace capacity ratings
American Adoption (1870s-1920s)
Late 19th Century: American industrial expansion embraced the BTU for:
- Railroad locomotive coal consumption
- Factory steam heating systems
- Urban gas lighting and heating (coal gas)
- Refrigeration industry development
Refrigeration "Ton" (1880s-1900s): The refrigeration industry defined cooling capacity based on ice production:
- 1 ton of refrigeration = melting 1 ton (2,000 lbs) of ice in 24 hours
- Ice melting heat: 144 BTU/lb × 2,000 lbs = 288,000 BTU per day
- Rate: 288,000 BTU ÷ 24 hours = 12,000 BTU/h
- This became the standard unit for air conditioning capacity
Natural Gas Industry (1900s-1920s): As natural gas distribution networks developed, utilities billed customers by BTU content:
- Gas heat value: approximately 1,000 BTU per cubic foot
- Therm (1920s): Defined as 100,000 BTU for convenient billing
- Still used in US natural gas bills today
Standardization (1920s-1960s)
International Steam Tables (1929-1956): International conferences standardized thermodynamic properties of water and steam, establishing:
- IT calorie (International Table calorie) = 4.1868 joules (exact)
- IT BTU = 1,055.05585262 joules (derived from IT calorie)
Post-WWII HVAC Boom (1940s-1960s): Residential air conditioning explosion in the United States:
- Room air conditioners rated in BTU/h (5,000, 8,000, 10,000, 12,000 BTU/h)
- Central AC systems in tons (1-ton, 2-ton, 3-ton, 5-ton)
- Furnaces and boilers rated in BTU/h input/output
UK/Commonwealth Metrication (1960s-1980s): Britain and Commonwealth nations transitioned to SI units:
- Joules (J) replaced BTU for energy
- Watts (W) replaced BTU/h for power
- Celsius replaced Fahrenheit
Modern Era: US Retention (1970s-Present)
1975 Energy Policy and Conservation Act: Mandated energy efficiency labeling for appliances using BTU-based metrics:
- EER (Energy Efficiency Ratio) = BTU/h output ÷ watts input
- AFUE (Annual Fuel Utilization Efficiency) = BTU output ÷ BTU input
- SEER (Seasonal Energy Efficiency Ratio) = BTU cooling ÷ watt-hours seasonal
Persistence in US Markets: Despite federal metrication efforts (1975 Metric Conversion Act), BTU remained dominant:
- HVAC contractors trained in BTU/h calculations
- Building codes specify BTU/h capacities
- Consumer familiarity ("12,000 BTU air conditioner")
- Industry infrastructure built around BTU standards
Current Status (2020s):
- US HVAC industry: 100% BTU-based
- Natural gas utilities: Billing in therms (100,000 BTU)
- Appliance ratings: Water heaters, furnaces, stoves in BTU/h
- Energy statistics: DOE reports in "quads" (quadrillion BTU)
While engineers often convert to SI units for calculations, BTU remains the commercial and consumer-facing standard in American energy markets.
Common Uses and Applications: electronvolts vs BTUs
Explore the typical applications for both Electronvolt (imperial/US) and British Thermal Unit (imperial/US) to understand their common contexts.
Common Uses for electronvolts
Atomic and Molecular Physics
Scientists use eV to describe:
- Ionization energies: Energy required to remove electrons from atoms
- Electron affinity: Energy released when electron attaches to atom
- Molecular orbital energies: HOMO-LUMO gaps, band structures
- Spectroscopy: Photon energies in UV-vis spectroscopy (200-800 nm ≈ 6-1.5 eV)
Example: UV photoelectron spectroscopy (UPS) measures electron binding energies from 0-50 eV.
Nuclear and Particle Physics
The electronvolt (especially MeV, GeV, TeV) is the universal energy unit:
Particle Accelerators:
- Beam energies: "The LHC collides protons at 6.8 TeV per beam"
- Collision center-of-mass energy: √s = 13.6 TeV
Nuclear Reactions:
- Q-values: Energy released/absorbed (e.g., D-T fusion Q = 17.6 MeV)
- Decay energies: Alpha, beta, gamma emissions
Particle Properties:
- Rest masses: Particle Data Group lists masses in MeV/c² or GeV/c²
- Decay channels: Energy distributions of decay products
Semiconductor Device Physics
Band gap energies determine electronic and optical properties:
Applications:
- Solar cells: Optimal band gap ~1.3-1.5 eV for maximum efficiency under solar spectrum
- LEDs: Emission color determined by band gap (red ~1.8 eV, blue ~3.1 eV)
- Transistors: Threshold voltages and switching energies
- Detectors: Ionization energies for particle detection (Si: 3.6 eV per electron-hole pair)
Radiation Dosimetry and Medical Physics
X-ray and gamma-ray energies specified in keV or MeV:
Medical Imaging:
- Mammography: 25-35 keV (soft tissue contrast)
- CT scans: 80-140 keV
- PET scans: 511 keV (positron-electron annihilation photons)
Radiation Therapy:
- External beam: 6-18 MeV photon beams
- Proton therapy: 70-250 MeV proton beams
Astrophysics and Cosmology
Photon energies across the electromagnetic spectrum:
Radio to Infrared: μeV to eV (microwave background ~0.0002 eV) Visible: 1.8-3.1 eV X-ray: keV to MeV (neutron star accretion, supernovae) Gamma-ray: MeV to GeV (active galactic nuclei, gamma-ray bursts) Ultra-high-energy cosmic rays: EeV (10¹⁸ eV) and beyond
Example: Fermi Gamma-ray Space Telescope detects photons from 20 MeV to >300 GeV.
Materials Science and Catalysis
Surface science and chemical reactions:
Techniques:
- XPS (X-ray Photoelectron Spectroscopy): Binding energies 0-1500 eV
- UPS (UV Photoelectron Spectroscopy): Valence band energies 0-50 eV
- Auger Electron Spectroscopy: Electron energies 50-2000 eV
Catalysis:
- Activation barriers: 0.1-3 eV for chemical reactions
- Adsorption energies: 0.5-5 eV for molecules on surfaces
When to Use BTUs
HVAC System Sizing and Selection
HVAC professionals calculate heating/cooling needs in BTU/h:
Cooling Load Calculation:
- Square footage: 20-25 BTU/h per sq ft (rule of thumb)
- Heat gain factors: Sun exposure, insulation, occupancy, appliances
- Room-by-room Manual J calculations (detailed engineering method)
Example: 1,500 sq ft home
- Basic: 1,500 × 20 = 30,000 BTU/h minimum (2.5 tons)
- With factors: 36,000 BTU/h recommended (3 tons)
Heating Load:
- Climate zone based (heating degree days)
- Insulation R-values
- Air infiltration rates
- Manual J detailed calculations
Natural Gas Billing and Pricing
US natural gas utilities bill in therms (100,000 BTU):
Typical Bill:
- Winter heating month: 150-300 therms (15-30 million BTU)
- Summer low usage: 10-30 therms (1-3 million BTU, cooking/water heating)
Pricing:
- Residential: $0.80-$2.00 per therm (varies by region, season)
- Commercial: $0.50-$1.50 per therm
- Industrial: $0.30-$1.00 per therm (bulk rates)
Appliance Energy Efficiency Ratings
EER (Energy Efficiency Ratio):
- Formula: EER = Cooling capacity (BTU/h) ÷ Power input (watts)
- Example: 12,000 BTU/h AC using 1,200 watts = EER 10.0
- Higher EER = more efficient
- Typical range: 8-13 for room ACs, 10-16 for central AC
SEER (Seasonal Energy Efficiency Ratio):
- Seasonal average efficiency = BTU cooling ÷ watt-hours consumed
- Minimum US standard: SEER 14 (as of 2023 for northern states)
- High-efficiency units: SEER 18-25
- Calculation accounts for varying outdoor temperatures
AFUE (Annual Fuel Utilization Efficiency):
- Percentage of fuel BTU converted to useful heat
- Minimum US standard: 80% AFUE for gas furnaces (mid-efficiency)
- High-efficiency: 90-98% AFUE (condensing furnaces)
- Example: 100,000 BTU/h input, 95% AFUE = 95,000 BTU/h heat output
Energy Content and Fuel Comparison
Industries compare fuels by BTU per unit:
Cost per Million BTU:
- Natural gas at $1.00/therm = $10.00 per million BTU
- Propane at $2.50/gallon = $27.32 per million BTU
- Heating oil at $3.50/gallon = $25.27 per million BTU
- Electricity at $0.12/kWh = $35.16 per million BTU
This allows consumers to compare heating costs across fuel types.
National and Industrial Energy Statistics
US Department of Energy uses "quad" (quadrillion BTU) for national statistics:
2022 US Energy Consumption (approximate):
- Total: 100 quads (100 × 10¹⁵ BTU)
- Petroleum: 36 quads
- Natural gas: 33 quads
- Coal: 10 quads
- Nuclear: 8 quads
- Renewables: 13 quads
Building Codes and Regulations
US building codes specify BTU requirements:
- Minimum ventilation: CFM (cubic feet per minute) and BTU/h heat loss
- Furnace sizing: BTU/h capacity requirements by climate zone
- Water heater recovery: Gallons per hour at ΔT or BTU/h rating
Additional Unit Information
About Electronvolt (eV)
How do I convert eV to joules?
Formula: Joules = eV × 1.602176634 × 10⁻¹⁹
Example: 5 eV to joules
- 5 × 1.602 × 10⁻¹⁹ = 8.01 × 10⁻¹⁹ J
Reverse (joules to eV): eV = J / (1.602 × 10⁻¹⁹)
What is an electronvolt in simple terms?
An electronvolt is the tiny amount of energy that one electron gains when it "falls" through an electric potential difference of one volt, similar to a ball rolling down a one-meter hill gaining gravitational potential energy.
Analogy: Imagine a tiny charged particle (electron) on a "voltage hill." Rolling it down a 1-volt slope gives it 1 eV of energy.
Why use electronvolts instead of joules?
Convenience: Atomic and subatomic energies are incredibly small in joules, making eV more practical:
- Hydrogen ionization: 13.6 eV vs. 2.18 × 10⁻¹⁸ J
- LHC collision: 13 TeV vs. 2.1 × 10⁻⁶ J
- Higgs boson mass: 125 GeV/c² vs. 2.2 × 10⁻²⁵ kg
Natural scale: The electronvolt matches the energy scales in atomic/nuclear/particle physics, just as kilometers are more natural than microinches for geography.
How is energy related to wavelength in eV?
Formula: E (eV) ≈ 1240 / λ (nm)
Precise formula: E = hc/λ = (1239.84193 eV·nm) / λ (nm)
Where:
- h = Planck's constant = 4.136 × 10⁻¹⁵ eV·s
- c = speed of light = 3 × 10⁸ m/s
Examples:
- Red light (620 nm): E = 1240 / 620 = 2.0 eV
- Blue light (400 nm): E = 1240 / 400 = 3.1 eV
- X-ray (0.1 nm): E = 1240 / 0.1 = 12,400 eV = 12.4 keV
What is the difference between eV and eV/c²?
- eV = unit of energy
- eV/c² = unit of mass (through E=mc²)
Example:
- Photon energy: 2 eV (pure energy, massless particle)
- Electron rest mass: 511 keV/c² (intrinsic mass)
- When electron at rest, its rest energy E₀ = mc² = 511 keV
Why divide by c²? To convert from energy units (eV) to mass units, divide by c² = (3 × 10⁸ m/s)².
How many eV in visible light?
Visible spectrum: approximately 1.8 eV (red) to 3.1 eV (violet)
Detailed breakdown:
- Red (700 nm): 1.77 eV
- Orange (620 nm): 2.00 eV
- Yellow (580 nm): 2.14 eV
- Green (520 nm): 2.38 eV
- Blue (470 nm): 2.64 eV
- Violet (400 nm): 3.10 eV
Why this range? Human eye evolved to detect solar spectrum peak output (~500 nm, 2.5 eV).
What is a kiloelectronvolt (keV)?
1 keV = 1,000 eV = 1.602 × 10⁻¹⁶ J
Typical applications:
- X-ray energies: 10-100 keV (medical, industrial)
- Inner-shell electron binding energies: 0.1-100 keV
- Low-energy nuclear transitions: 1-1000 keV
- Electron microscope beam energies: 100-300 keV
What is the energy of thermal motion at room temperature?
Room temperature (T = 300 K): kBT ≈ 0.026 eV = 26 meV (millielectronvolts)
Where:
- kB = Boltzmann constant = 8.617 × 10⁻⁵ eV/K
- T = absolute temperature in kelvins
Significance:
- Explains why chemical bonds (1-10 eV) don't spontaneously break at room temperature
- Thermal energy << bond energy, so molecular stability maintained
- Important for semiconductor physics: band gap >> kBT for good insulator
How much energy is in a MeV?
1 MeV (megaelectronvolt) = 1,000,000 eV = 1.602 × 10⁻¹³ J
Typical MeV-scale phenomena:
- Nuclear binding energies: ~8 MeV per nucleon
- Gamma rays: 0.1-10 MeV
- Positron-electron annihilation: 2 × 0.511 = 1.022 MeV (two 511 keV photons)
- Alpha particle decay energies: 4-9 MeV
- Nuclear fission fragments: 50-200 MeV
What is the Higgs boson mass in eV?
Higgs boson mass: mH ≈ 125.1 GeV/c²
Discovered at CERN's Large Hadron Collider (LHC) on July 4, 2012.
Context:
- About 133 times heavier than a proton (938 MeV/c²)
- Equivalent to approximately 133 hydrogen atoms in mass
- In kilograms: 2.24 × 10⁻²⁵ kg (incredibly tiny, but "heavy" for elementary particles)
The Higgs boson's mass is crucial to understanding the Higgs mechanism, which gives fundamental particles their mass through interaction with the Higgs field.
Can you use eV for macroscopic energies?
Technically yes, but impractical:
Examples:
- 1 joule = 6.242 × 10¹⁸ eV (6 billion billion eV!)
- 1 kilowatt-hour (kWh) = 3.6 × 10⁶ J = 2.25 × 10²⁵ eV
- AA battery (3 Wh) = 6.75 × 10²² eV
Why not used: Numbers become absurdly large. The electronvolt is designed for atomic/molecular/nuclear scales, not everyday human-scale energies.
Exception: Ultra-high-energy cosmic rays occasionally reach macroscopic energies:
- Oh-My-God particle (1991): 3 × 10²⁰ eV ≈ 51 joules (energy of baseball at 100 km/h)
About British Thermal Unit (BTU)
How many BTUs do I need for air conditioning?
Rule of thumb: 20-25 BTU per square foot for cooling in moderate climates.
Examples:
- 500 sq ft room: 10,000-12,500 BTU/h → 10,000 or 12,000 BTU/h unit
- 1,000 sq ft: 20,000-25,000 BTU/h → 2-ton (24,000 BTU/h) central AC
- 1,500 sq ft: 30,000-37,500 BTU/h → 3-ton (36,000 BTU/h) system
Factors increasing BTU needs:
- Hot climate (southern US)
- Poor insulation
- Large windows or south/west exposure
- High ceilings
- Many heat-generating appliances
Professional sizing: Use Manual J load calculation for accurate sizing.
What is 12,000 BTU/h?
12,000 BTU/h = 1 ton of refrigeration = 3.517 kW cooling capacity
Origin: Amount of cooling from melting 1 ton (2,000 pounds) of ice over 24 hours.
Common AC sizes based on tons:
- 0.5 ton = 6,000 BTU/h (very small room)
- 1 ton = 12,000 BTU/h (large room or small apartment)
- 1.5 tons = 18,000 BTU/h (2-3 rooms)
- 2 tons = 24,000 BTU/h (small house, ~1,200-1,500 sq ft)
- 3 tons = 36,000 BTU/h (medium house, ~1,500-2,100 sq ft)
How do I convert BTU to kWh?
Formula: kWh = BTU ÷ 3,412.14
Example: 10,000 BTU = 10,000 ÷ 3,412 = 2.93 kWh
Reverse: BTU = kWh × 3,412.14
- 5 kWh = 5 × 3,412 = 17,060 BTU
For power (BTU/h to kW): kW = BTU/h ÷ 3,412.14
- 24,000 BTU/h = 24,000 ÷ 3,412 = 7.03 kW (2-ton AC)
What is a therm in natural gas billing?
1 therm = 100,000 BTU exactly
US natural gas utilities bill in therms rather than BTU for convenience.
Typical household usage:
- Winter month (heating): 150-300 therms (15-30 million BTU)
- Summer month (cooking/water heating only): 10-30 therms (1-3 million BTU)
Relationship to volume:
- Natural gas heat content: ~1,000-1,030 BTU per cubic foot (varies)
- 1 therm ≈ 97-100 cubic feet (CCF = hundred cubic feet)
- Some utilities bill in CCF, approximately equivalent to 1 therm
How efficient are different heating fuels in BTU per dollar?
Example comparison (prices vary by region and time):
Assuming: Natural gas $1.00/therm, Propane $2.50/gal, Heating oil $3.50/gal, Electricity $0.12/kWh
Cost per million BTU:
- Natural gas: $10.00 per million BTU (most economical)
- Propane: $27.32 per million BTU
- Heating oil: $25.27 per million BTU
- Electricity: $35.16 per million BTU (expensive for heating, but 100% efficient at point of use)
With efficiency factored in (95% gas furnace vs. electric baseboard):
- Natural gas: $10.00 / 0.95 = $10.53 per million BTU delivered heat
- Electric: $35.16 / 1.00 = $35.16 per million BTU delivered heat
- Heat pump (COP 3.0): $35.16 / 3.0 = $11.72 per million BTU (competitive with gas!)
What is EER for air conditioners?
EER (Energy Efficiency Ratio) = Cooling output (BTU/h) ÷ Power input (watts)
Example: 12,000 BTU/h AC using 1,000 watts
- EER = 12,000 ÷ 1,000 = 12.0
Typical ranges:
- Old units: EER 8-10
- Standard efficiency: EER 10-12
- High efficiency: EER 12-14+
Higher EER = more efficient = lower operating cost
Related metric - SEER (Seasonal EER):
- Accounts for varying outdoor temperatures throughout season
- Minimum US standard: SEER 14 (2023)
- High-efficiency: SEER 18-25
How many BTU does the human body produce?
Resting: 250-350 BTU/h (sitting, sleeping) Light activity: 400-500 BTU/h (office work, reading) Moderate activity: 600-800 BTU/h (walking, cooking) Heavy activity: 1,000-1,500 BTU/h (exercise, manual labor)
Example: Office with 20 people
- 20 people × 400 BTU/h = 8,000 BTU/h heat gain
- AC system must remove this heat plus external and equipment heat loads
HVAC design accounts for occupancy heat gain when sizing systems.
Can I use a propane heater indoors?
Depends on heater type and ventilation:
Vented (direct vent, B-vent): YES
- Exhausts combustion gases outside
- Safe for indoor use
- Rated in BTU/h (e.g., 30,000 BTU/h)
Ventless/vent-free: SOMETIMES (check local codes)
- Designed with oxygen depletion sensor (ODS)
- Many jurisdictions restrict or ban ventless propane indoors
- Produces water vapor and consumes oxygen
- Typical: 10,000-30,000 BTU/h
Outdoor propane heaters: NO (for indoors)
- Patio heaters (40,000+ BTU/h) produce too much CO and consume too much oxygen
- Designed for outdoor use only
Safety: Carbon monoxide detector mandatory for any combustion appliance.
What BTU rating do I need for a water heater?
Depends on household size and usage:
Gas Water Heaters (tank):
- 1-2 people: 30,000-36,000 BTU/h (30-40 gallon tank)
- 3-4 people: 36,000-38,000 BTU/h (40-50 gallon tank)
- 5+ people: 38,000-50,000 BTU/h (50-75 gallon tank)
Tankless Gas (on-demand):
- 1-2 fixtures: 140,000-180,000 BTU/h (small unit)
- 3-4 fixtures: 180,000-200,000 BTU/h (whole-house)
Electric (measured in kW, convert: 1 kW ≈ 3,412 BTU/h):
- 40-gallon: 4.5-5.5 kW (15,000-19,000 BTU/h equivalent)
- 50-gallon: 5.5-6.0 kW (19,000-20,000 BTU/h equivalent)
Recovery rate matters: BTU/h determines how quickly tank reheats after use.
How much does it cost to run a 10,000 BTU/h air conditioner?
Energy consumption: 10,000 BTU/h ÷ 3,412 BTU/kWh = 2.93 kW (if 100% efficient, which no AC is)
Actual power draw (assuming EER 10.0): 10,000 BTU/h ÷ 10 EER = 1,000 watts = 1 kW
Operating cost (assuming $0.12/kWh electricity rate):
- Per hour: 1 kW × $0.12 = $0.12/hour
- 8 hours/day: $0.96/day = $28.80/month
- 24/7 (30 days): $86.40/month
Variables affecting cost:
- EER rating (higher = lower cost)
- Electricity rate (varies $0.08-$0.30/kWh by region)
- Usage hours per day
- Outdoor temperature (hotter = longer run time)
Conversion Table: Electronvolt to British Thermal Unit
| Electronvolt (eV) | British Thermal Unit (BTU) |
|---|---|
| 0.5 | 0 |
| 1 | 0 |
| 1.5 | 0 |
| 2 | 0 |
| 5 | 0 |
| 10 | 0 |
| 25 | 0 |
| 50 | 0 |
| 100 | 0 |
| 250 | 0 |
| 500 | 0 |
| 1,000 | 0 |
People Also Ask
How do I convert Electronvolt to British Thermal Unit?
To convert Electronvolt to British Thermal Unit, enter the value in Electronvolt in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our energy converter page to convert between other units in this category.
Learn more →What is the conversion factor from Electronvolt to British Thermal Unit?
The conversion factor depends on the specific relationship between Electronvolt and British Thermal Unit. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert British Thermal Unit back to Electronvolt?
Yes! You can easily convert British Thermal Unit back to Electronvolt by using the swap button (⇌) in the calculator above, or by visiting our British Thermal Unit to Electronvolt converter page. You can also explore other energy conversions on our category page.
Learn more →What are common uses for Electronvolt and British Thermal Unit?
Electronvolt and British Thermal Unit are both standard units used in energy measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our energy converter for more conversion options.
For more energy conversion questions, visit our FAQ page or explore our conversion guides.
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Other Energy Units and Conversions
Explore other energy units and their conversion options:
- Joule (J) • Electronvolt to Joule
- Kilojoule (kJ) • Electronvolt to Kilojoule
- Megajoule (MJ) • Electronvolt to Megajoule
- Gigajoule (GJ) • Electronvolt to Gigajoule
- Watt-hour (Wh) • Electronvolt to Watt-hour
- Kilowatt-hour (kWh) • Electronvolt to Kilowatt-hour
- Megawatt-hour (MWh) • Electronvolt to Megawatt-hour
- Calorie (cal) • Electronvolt to Calorie
- Kilocalorie (kcal) • Electronvolt to Kilocalorie
- Therm (therm) • Electronvolt to Therm
Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — Fundamental physical constants and unit conversions
Bureau International des Poids et Mesures — International System of Units (SI) definitions and standards
International Organization for Standardization — Quantities and units international standards series
Last verified: December 3, 2025