Kilowatt-hour to British Thermal Unit Converter
Convert kilowatt-hours to BTUs with our free online energy converter.
Quick Answer
1 Kilowatt-hour = 3412.12822 BTUs
Formula: Kilowatt-hour × conversion factor = British Thermal Unit
Use the calculator below for instant, accurate conversions.
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Kilowatt-hour to British Thermal Unit Calculator
How to Use the Kilowatt-hour to British Thermal Unit Calculator:
- Enter the value you want to convert in the 'From' field (Kilowatt-hour).
- 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 Kilowatt-hour to British Thermal Unit: Step-by-Step Guide
Converting Kilowatt-hour to British Thermal Unit involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
BTU = kWh × 3412.13Example Calculation:
1 kWh = 3412.12822 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 Kilowatt-hour and a British Thermal Unit?
and Standards
The kilowatt-hour is defined as the energy equivalent of one kilowatt (1,000 watts) of power sustained for one hour:
1 kWh = 1,000 W × 1 hour = 3,600,000 joules = 3.6 megajoules
Precise Equivalents
- 1 kWh = 3,600,000 J (exactly)
- 1 kWh = 3.6 MJ (exactly)
- 1 kWh = 1.341 horsepower-hours (mechanical)
- 1 kWh = 859.845 kilocalories (thermochemical)
- 1 kWh = 3,412.14 British thermal units (BTU)
- 1 kWh = 2.655 × 10²² electronvolts
The kilowatt-hour is not an SI unit (the SI unit of energy is the joule), but it is explicitly accepted for use alongside SI units by the International Bureau of Weights and Measures (BIPM) due to its universal adoption in electrical energy metering and commerce.
Power vs. Energy: The Critical Distinction
Kilowatt (kW) measures power—the rate at which energy is being used or generated at a specific moment (analogous to speed on a speedometer).
Kilowatt-hour (kWh) measures energy—the total amount of energy used or generated over time (analogous to distance traveled on an odometer).
Relationship: Energy (kWh) = Power (kW) × Time (hours)
Example: A 2 kW space heater running for 3 hours consumes 2 kW × 3 h = 6 kWh of energy.
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 Kilowatt-hour 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 Kilowatt-hour and British Thermal Unit
and Evolution
The Birth of Electrical Metering (1880s-1890s)
The kilowatt-hour emerged from the practical needs of early electrical utilities. When Thomas Edison opened the Pearl Street Station in Manhattan in September 1882—the world's first commercial central power plant—he needed a way to bill customers for electricity consumption. Early meters measured current flow, but this didn't account for voltage or time, making fair billing difficult.
The breakthrough came with the development of the induction watt-hour meter by Oliver B. Shallenberger in 1888, working for Westinghouse. This electromechanical device used electromagnetic induction to rotate a disc at a speed proportional to power consumption, with the total rotations indicating energy consumed—directly measuring kilowatt-hours. This meter design, refined but fundamentally unchanged, remained the global standard for over a century until the recent transition to digital smart meters.
Standardization and the International Electrical Congress (1893)
The International Electrical Congress held during the 1893 World's Columbian Exposition in Chicago formally adopted standardized electrical units. While the joule was recognized as the scientific unit of energy, the kilowatt-hour was established as the practical unit for electrical power distribution and billing. This dual system—joules in science, kilowatt-hours in commerce—continues today.
Samuel Insull and Modern Utility Economics (1890s-1920s)
Samuel Insull, president of Chicago Edison Company (later Commonwealth Edison), revolutionized the electricity industry in the 1890s by implementing sophisticated pricing structures based on kilowatt-hour consumption. Insull pioneered:
- Load factor optimization: Encouraging off-peak usage through lower kWh rates
- Declining block rates: Lower per-kWh prices for higher consumption, incentivizing electrification
- Demand charges: Separate charges for peak power demand (kW) versus energy consumption (kWh) for industrial customers
Insull's innovations made electricity affordable for middle-class households, transforming it from a luxury to a necessity and accelerating the electrification of America and the world.
The Electrification Revolution (1920s-1960s)
By the 1920s, the kilowatt-hour had become universal for electricity billing in industrialized nations. Rural electrification programs—such as the U.S. Rural Electrification Administration (1935)—brought kilowatt-hour metering to millions of farms and small towns. Post-World War II economic growth drove massive increases in electrical consumption, measured everywhere in kilowatt-hours.
Modern Era: Smart Meters and Real-Time kWh (2000s-Present)
The 21st century brought smart meters that measure kilowatt-hour consumption digitally, often in 15-minute or hourly intervals. These enable:
- Time-of-use (TOU) pricing: Different per-kWh rates based on time of day
- Real-time monitoring: Customers can track kWh usage in real time via apps
- Demand response: Automated load reduction during peak demand
- Net metering: Bidirectional kWh measurement for solar panel owners
Today, kilowatt-hours are also the standard unit for electric vehicle battery capacity, solar panel production, energy efficiency ratings, and carbon footprint calculations tied to electricity consumption.
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: kilowatt-hours vs BTUs
Explore the typical applications for both Kilowatt-hour (imperial/US) and British Thermal Unit (imperial/US) to understand their common contexts.
Common Uses for kilowatt-hours
1. Electricity Billing (Residential, Commercial, Industrial)
The kilowatt-hour is the universal unit for billing electrical energy consumption worldwide. Your electric utility meter tracks cumulative kilowatt-hours, and your monthly bill reflects the total kWh consumed multiplied by your rate structure.
Typical billing components:
- Energy charge: $0.08-0.35 per kWh (varies by location and utility)
- Delivery/distribution charge: Often a separate per-kWh fee
- Fixed charges: Monthly connection fees independent of kWh
- Demand charges (commercial/industrial): Based on peak kW demand
Example bill calculation (900 kWh residential):
- Energy: 900 kWh × $0.12 = $108.00
- Delivery: 900 kWh × $0.04 = $36.00
- Fixed charge: $10.00
- Total: $154.00
2. Appliance Energy Efficiency Ratings
EnergyGuide labels in the US and Canada display estimated annual kilowatt-hour consumption:
- Refrigerators: 300-700 kWh/year
- Dishwashers: 200-400 kWh/year
- Washing machines: 150-500 kWh/year
Energy Star certification requires appliances to use fewer kWh than standard models, typically 10-50% more efficient.
3. Electric Vehicle Specifications
EV manufacturers specify battery capacity in kilowatt-hours, directly comparable across all brands:
- Small battery: 40-50 kWh (city cars, ~150-200 miles)
- Medium battery: 60-75 kWh (mainstream EVs, ~250-300 miles)
- Large battery: 85-100 kWh (luxury/performance EVs, ~350-400 miles)
- Truck/SUV battery: 100-200+ kWh (heavy vehicles, towing capability)
Efficiency metric: Miles per kWh (analogous to miles per gallon for gasoline vehicles)
4. Solar and Renewable Energy Production
Solar installers and monitoring systems display production in kilowatt-hours:
- Real-time production: "Currently generating 4.2 kW"
- Daily total: "Produced 28 kWh today"
- Lifetime total: "System has produced 47,500 kWh since installation"
Net metering: Bidirectional meters track both kWh consumed from the grid and kWh exported to the grid, with the difference billed (or credited) monthly.
5. Carbon Footprint Calculations
Carbon emissions from electricity are calculated using kilowatt-hour consumption multiplied by regional grid intensity:
Grid carbon intensity (kg CO₂ per kWh):
- Coal-heavy grid: 0.8-1.0 kg CO₂/kWh (e.g., Wyoming, West Virginia)
- US average: ~0.4 kg CO₂/kWh
- Natural gas grid: 0.4-0.5 kg CO₂/kWh
- Renewable-heavy grid: 0.02-0.1 kg CO₂/kWh (e.g., Iceland, Norway, Quebec)
Example: 900 kWh monthly consumption × 0.4 kg CO₂/kWh = 360 kg CO₂ = 0.36 metric tons CO₂ per month
6. Battery Storage Systems (Home and Grid)
Home battery storage (e.g., Tesla Powerwall) and grid-scale battery systems specify capacity in kilowatt-hours:
- Tesla Powerwall 2: 13.5 kWh usable capacity
- LG Chem RESU: 9.8-16 kWh
- Sonnen eco: 5-15 kWh (modular)
Backup capability: A 13.5 kWh battery can power essential loads (refrigerator, lights, WiFi, phone charging) for 1-2 days during an outage.
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 Kilowatt-hour (kWh)
How much does 1 kWh of electricity cost?
Electricity rates vary widely by location, utility, rate structure, and time of day:
US average (2024): $0.13-0.16 per kWh (residential)
By state (residential, wide variation):
- Lowest: Louisiana (~$0.09/kWh), Oklahoma (~$0.10/kWh), Arkansas (~$0.10/kWh)
- Highest: Hawaii (~$0.40/kWh), California (~$0.25-0.35/kWh), Massachusetts (~$0.24/kWh)
- Typical ranges: Most states $0.10-0.18/kWh
International comparison:
- Denmark: ~$0.40/kWh (highest in developed world)
- Germany: ~$0.35/kWh
- UK: ~$0.25-0.30/kWh (£0.20-0.24/kWh)
- Canada: ~$0.08-0.12/kWh (varies by province)
- China: ~$0.08/kWh (residential)
Commercial rates are typically 20-40% lower than residential ($0.08-0.12/kWh in US), while industrial rates are often 40-60% lower ($0.05-0.08/kWh) due to higher volumes and lower distribution costs.
Time-of-use (TOU) rates vary by time:
- Off-peak (midnight-6am): $0.08-0.12/kWh
- Mid-peak (daytime): $0.12-0.18/kWh
- On-peak (5-9pm): $0.20-0.40/kWh
What is the difference between kW and kWh?
This is one of the most common sources of confusion in electricity:
Kilowatt (kW) measures POWER—the rate of energy use or generation at a specific instant.
- Analogous to: Speed (miles per hour on speedometer)
- Measures: How fast energy is being used right now
- Example: "My air conditioner is currently drawing 3.5 kW"
Kilowatt-hour (kWh) measures ENERGY—the total amount of energy used or generated over time.
- Analogous to: Distance (total miles traveled on odometer)
- Measures: How much energy was used over a period
- Example: "My air conditioner used 28 kWh today (3.5 kW × 8 hours)"
Relationship: Energy (kWh) = Power (kW) × Time (hours)
Another analogy: Think of filling a bathtub:
- kW = flow rate (gallons per minute from faucet)
- kWh = total water (total gallons in tub)
- Fast flow × short time = Slow flow × long time = same total water
Billing distinction: You're billed for energy (kWh), not power (kW)—except for commercial "demand charges" based on peak kW.
How many kWh does an average home use per day?
US average: ~30 kWh per day (~900 kWh per month, ~10,800 kWh per year)
Breakdown by category (typical US home):
- Heating/cooling: 40-45% (~12-14 kWh/day)
- Water heating: 14-18% (~4-5 kWh/day)
- Appliances: 25-30% (~8-9 kWh/day)
- Lighting: 6-10% (~2-3 kWh/day)
- Electronics: 5-8% (~2 kWh/day)
Variation by home type:
- Apartment (500-800 sq ft): 15-20 kWh/day
- Small house (1,000-1,500 sq ft): 20-25 kWh/day
- Medium house (1,500-2,500 sq ft): 25-35 kWh/day
- Large house (2,500-4,000 sq ft): 35-50 kWh/day
- Very large home (4,000+ sq ft): 50-100+ kWh/day
Seasonal variation:
- Winter (heating climate): 30-50 kWh/day
- Spring/Fall: 20-30 kWh/day
- Summer (cooling climate): 35-60 kWh/day
Geographic variation (US average by region):
- South (Louisiana, Texas, Florida): 35-45 kWh/day (high AC usage)
- West (California, Oregon): 20-30 kWh/day (mild climate)
- Northeast (New York, Massachusetts): 25-30 kWh/day
- Midwest (Illinois, Ohio): 28-35 kWh/day
How do I calculate my appliance's kWh usage?
Formula: kWh = (Watts ÷ 1,000) × Hours of use
Step-by-step:
- Find wattage: Check appliance label or manual (or use a Kill-A-Watt meter)
- Convert to kilowatts: Divide watts by 1,000
- Multiply by hours: Total hours of operation
- Result is kWh: Total energy consumed
Example 1 (Simple continuous use):
- 60-watt light bulb
- Used 5 hours per day
- kWh per day = (60 ÷ 1,000) × 5 = 0.06 × 5 = 0.3 kWh
- Monthly = 0.3 × 30 = 9 kWh
- Cost = 9 kWh × $0.15 = $1.35 per month
Example 2 (Cycling appliance):
- Refrigerator with 150-watt compressor
- Runs ~8 hours per day (33% duty cycle)
- kWh per day = (150 ÷ 1,000) × 8 = 0.15 × 8 = 1.2 kWh
- Yearly = 1.2 × 365 = 438 kWh
- Cost = 438 kWh × $0.15 = $65.70 per year
Example 3 (High-power short duration):
- Electric oven, 3,000 watts
- Used 1 hour per day
- kWh per day = (3,000 ÷ 1,000) × 1 = 3 kWh
- Monthly = 3 × 30 = 90 kWh
- Cost = 90 kWh × $0.15 = $13.50 per month
Tip: For cycling appliances (refrigerators, AC, heaters), check EnergyGuide labels for actual annual kWh rather than calculating from power ratings.
How many kWh does it take to charge an electric vehicle?
Charging kWh depends on battery size and state of charge:
Formula: kWh needed = Battery capacity (kWh) × (% to charge ÷ 100) ÷ Charging efficiency
Charging efficiency: ~85-95% (some energy lost to heat)
Example 1 (Typical daily charging):
- Tesla Model 3 Long Range (82 kWh battery)
- Daily driving uses 40% of battery (33 kWh)
- Charging efficiency: 90%
- kWh from wall = 33 ÷ 0.90 = 36.7 kWh
- Cost at $0.15/kWh = $5.50 per charge
Example 2 (Empty to full):
- Nissan Leaf (62 kWh battery)
- Charging from 10% to 100% (90% of capacity)
- kWh needed = 62 × 0.90 = 55.8 kWh
- With 90% efficiency = 55.8 ÷ 0.90 = 62 kWh
- Cost at $0.12/kWh = $7.44 full charge
Charging levels:
- Level 1 (120V, 12A): ~1.4 kW → ~1.4 kWh per hour (very slow)
- Level 2 (240V, 32A): ~7.7 kW → ~7.7 kWh per hour (home charging)
- DC Fast Charging: 50-350 kW → 50-350 kWh per hour (public fast charging)
Annual EV consumption (typical):
- 12,000 miles per year ÷ 4 miles per kWh = 3,000 kWh per year
- Cost at $0.15/kWh = $450 per year
- Gasoline equivalent (25 MPG, $3.50/gal): 480 gallons = $1,680 per year
- Savings: ~$1,200 per year
How many kilowatt-hours are in a gallon of gasoline?
Gasoline contains approximately 33.7 kWh of chemical energy per gallon (based on lower heating value).
However, internal combustion engines are only 20-30% efficient at converting this to mechanical work, while electric motors are 85-95% efficient.
Effective comparison:
- 1 gallon gasoline = 33.7 kWh chemical energy
- Usable mechanical energy = 33.7 × 0.25 (avg efficiency) = 8.4 kWh
- Electric vehicle uses 8.4 kWh directly from battery = equivalent to ~1 gallon gasoline
Example: A 25 MPG gas car vs. 4 miles/kWh EV:
- Gas car: 100 miles ÷ 25 MPG = 4 gallons = 134.8 kWh chemical energy (33.7 usable)
- EV: 100 miles ÷ 4 mi/kWh = 25 kWh from battery
- Efficiency advantage: EV uses ~25% of the energy (25 kWh vs. 100 kWh delivered fuel)
Cost comparison (at $3.50/gal gasoline, $0.15/kWh electricity):
- Gas: 4 gallons × $3.50 = $14.00 per 100 miles
- Electric: 25 kWh × $0.15 = $3.75 per 100 miles
- Savings: $10.25 per 100 miles, or ~73% cheaper
What is a megawatt-hour (MWh) or gigawatt-hour (GWh)?
These are larger units used for industrial, utility, and national-scale energy:
Megawatt-hour (MWh): 1 MWh = 1,000 kWh
- Scale: Enough for ~1.5 months of average US household consumption
- Uses: Large commercial buildings, small industrial facilities, utility contracts
- Example: A small office building might use 50-100 MWh per month
Gigawatt-hour (GWh): 1 GWh = 1,000 MWh = 1,000,000 kWh
- Scale: Enough for ~100 US homes for one year
- Uses: Large industrial plants, small utility service territories, data centers
- Example: A medium-sized data center uses 10-50 GWh per year
Terawatt-hour (TWh): 1 TWh = 1,000 GWh = 1,000,000 MWh = 1,000,000,000 kWh
- Scale: National and global electricity consumption
- Example: California uses ~290 TWh per year; US total ~4,000 TWh per year
Power plant output example:
- 1,000 MW (1 GW) nuclear plant running continuously for 1 year:
- 1,000 MW × 8,760 hours/year = 8,760 GWh = 8.76 TWh
How accurate are electricity meters?
Modern electricity meters are extremely accurate:
Electromechanical meters (older spinning disc meters):
- Accuracy: ±1-2% over most load ranges
- More accurate at higher loads, less accurate at very low loads
- Degrade slowly over time; calibrated to read slightly high initially
Digital smart meters (solid-state):
- Accuracy: ±0.5-1% across all load ranges
- Highly accurate even at very low loads (phantom/standby power)
- Consistent accuracy over time (no mechanical wear)
Regulatory standards (US):
- ANSI C12.20 Class 0.2: ±0.2% accuracy (revenue-grade meters)
- Utilities must test meters periodically; out-of-spec meters must be replaced
Practical impact: A 1% error on a 1,000 kWh monthly bill = 10 kWh = $1-2 difference. Given meters tend to read slightly high, customers rarely underpay.
If you suspect meter error:
- Check for obvious high-consumption causes (always-on appliances, inefficient equipment)
- Turn off all breakers except one circuit; use a known load (e.g., 1,000W heater) and time it
- Request utility meter test (usually free or low-cost; if meter is faulty, utility pays; if accurate, small fee)
Can I run my house on a generator? How many kWh?
Generator sizing: Based on power (kW), not energy (kWh)
Average home needs:
- Essential loads only (fridge, lights, electronics): 2-4 kW
- Partial home (add well pump, sump pump, furnace): 5-7 kW
- Whole home without AC: 8-12 kW
- Whole home with central AC: 15-22 kW
Fuel consumption and kWh:
- Portable generators: ~0.5-0.75 gallons/hour per kW output
- Example: 5 kW generator at 50% load (2.5 kW) uses ~1.5 gal/hr
- Running 8 hours = 12 gallons = 12 × 33.7 kWh = 404 kWh chemical → ~100 kWh electrical @ 25% efficiency
Cost comparison:
- Grid electricity: 100 kWh × $0.15 = $15.00
- Generator: 12 gallons × $3.50/gal = $42.00 (plus maintenance, noise, emissions)
Battery backup alternative: A 13.5 kWh Tesla Powerwall can provide 13.5 kWh of energy (enough for essential loads for 1-2 days during outage), recharged by solar or grid.
How many solar panels do I need to generate X kWh?
Solar panel output: 250-400 watts per panel (newer panels ~350-400W)
Production formula: kWh = Panel wattage (kW) × Peak sun hours × System derate
Peak sun hours (daily average, varies by location and season):
- Southwest US (Arizona, Nevada): 5.5-7 hours
- California: 5-6 hours
- Southern US: 4.5-5.5 hours
- Northern US: 3.5-4.5 hours
System derate factor: ~0.75-0.80 (accounts for inverter efficiency, shading, temperature, wiring losses)
Example 1 (30 kWh per day in Arizona):
- Target: 30 kWh/day
- Location: Phoenix (6 peak sun hours)
- System needed: 30 ÷ (6 × 0.77) = 6.5 kW system
- Number of 350W panels: 6,500 W ÷ 350 W/panel = 19 panels
- Annual production: 30 kWh/day × 365 = 10,950 kWh/year
Example 2 (900 kWh per month in Massachusetts):
- Target: 900 kWh/month = 30 kWh/day
- Location: Boston (4 peak sun hours)
- System needed: 30 ÷ (4 × 0.77) = 9.7 kW system
- Number of 350W panels: 9,700 W ÷ 350 W/panel = 28 panels
Rule of thumb: In average US locations (4.5 peak sun hours), a 1 kW system produces ~1,300-1,500 kWh per year.
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: Kilowatt-hour to British Thermal Unit
| Kilowatt-hour (kWh) | British Thermal Unit (BTU) |
|---|---|
| 0.5 | 1,706.064 |
| 1 | 3,412.128 |
| 1.5 | 5,118.192 |
| 2 | 6,824.256 |
| 5 | 17,060.641 |
| 10 | 34,121.282 |
| 25 | 85,303.206 |
| 50 | 170,606.411 |
| 100 | 341,212.822 |
| 250 | 853,032.055 |
| 500 | 1,706,064.11 |
| 1,000 | 3,412,128.22 |
People Also Ask
How do I convert Kilowatt-hour to British Thermal Unit?
To convert Kilowatt-hour to British Thermal Unit, enter the value in Kilowatt-hour 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 Kilowatt-hour to British Thermal Unit?
The conversion factor depends on the specific relationship between Kilowatt-hour 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 Kilowatt-hour?
Yes! You can easily convert British Thermal Unit back to Kilowatt-hour by using the swap button (⇌) in the calculator above, or by visiting our British Thermal Unit to Kilowatt-hour converter page. You can also explore other energy conversions on our category page.
Learn more →What are common uses for Kilowatt-hour and British Thermal Unit?
Kilowatt-hour 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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Explore other energy units and their conversion options:
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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
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Last verified: February 19, 2026