Price Per Btu Calculator
This calculator helps you determine the true cost of heat by standardizing fuel prices into a single, comparable unit: cost per Million BTUs (MMBtu).
Simply select your fuel source and enter the price you pay per unit (e.g., per gallon, per therm, or per kWh) to see the effective cost of energy. This allows for a direct "apples-to-apples" comparison of heating costs.
Enter Fuel Type & Price
True Cost of Heat
Use this value to compare different fuel sources directly.
Understanding BTUs & Fuel Cost Comparison
What is a BTU and an MMBtu?
A BTU (British Thermal Unit) is the fundamental unit of heat energy. It represents the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. However, comparing fuels by a single BTU isn't practical, so the industry uses MMBtu, which stands for one Million BTUs.
By converting the price of any fuel (gallons of propane, therms of gas, kWh of electricity) into a standard cost per MMBtu, we can accurately compare which one offers more heat for the money.
The Role of Appliance Efficiency
This calculator determines the raw energy cost of the fuel itself. The final cost to heat your home also depends on your furnace or boiler's efficiency. An Annual Fuel Utilization Efficiency (AFUE) rating tells you how much of the fuel's energy is converted into usable heat.
- A furnace with 80% AFUE means 80¢ of every dollar spent on fuel becomes heat, while 20¢ is lost (e.g., up the chimney).
- A high-efficiency furnace with 95% AFUE only loses 5¢ of every dollar.
To find your true delivered cost, divide the calculator's result by your appliance's efficiency: Delivered Cost = (Cost per MMBtu) / (AFUE as decimal).
10 Real-Life Examples
Example 1: Comparing Propane vs. Heating Oil
Scenario: A homeowner can use either propane or heating oil. Propane costs $3.20/gallon and heating oil costs $4.10/gallon.
1. Propane Calculation: Price is $3.20. One gallon has ~91,500 BTUs.
Cost per MMBtu = ($3.20 / 91,500) * 1,000,000 = $34.97
2. Heating Oil Calculation: Price is $4.10. One gallon has ~138,700 BTUs.
Cost per MMBtu = ($4.10 / 138,700) * 1,000,000 = $29.56
Conclusion: Despite the higher price per gallon, heating oil is the more cost-effective fuel source in this case.
Example 2: Cost of Electric Baseboard Heating
Scenario: A cabin uses electric baseboard heaters (which are 100% efficient but use an expensive energy source). The electricity rate is $0.18 per kWh.
1. Known Values: Price is $0.18. One kWh has 3,412 BTUs.
2. Calculation:
Cost per MMBtu = ($0.18 / 3,412) * 1,000,000 = $52.75
Conclusion: The raw energy from electricity is significantly more expensive than most fossil fuels, costing $52.75 per MMBtu.
Example 3: Affordable Natural Gas
Scenario: A suburban home is connected to a natural gas line with a rate of $1.35 per Therm.
1. Known Values: Price is $1.35. One Therm has 100,000 BTUs.
2. Calculation:
Cost per MMBtu = ($1.35 / 100,000) * 1,000,000 = $13.50
Conclusion: Natural gas is often the cheapest heating fuel, costing only $13.50 per MMBtu in this example.
Example 4: Off-Grid Cabin with Kerosene
Scenario: An off-grid cabin uses a kerosene heater. The price for kerosene is $4.50 per gallon.
1. Known Values: Price is $4.50. One gallon of kerosene has ~135,000 BTUs.
2. Calculation:
Cost per MMBtu = ($4.50 / 135,000) * 1,000,000 = $33.33
Conclusion: Kerosene's energy cost is $33.33 per MMBtu, comparable to propane.
Example 5: Factoring in Furnace Efficiency
Scenario: Using the propane cost from Example 1 ($34.97/MMBtu), compare the final cost for an old 75% AFUE furnace vs. a new 95% AFUE furnace.
1. Old Furnace (75% AFUE):
Delivered Cost = $34.97 / 0.75 = $46.63 per MMBtu
2. New Furnace (95% AFUE):
Delivered Cost = $34.97 / 0.95 = $36.81 per MMBtu
Conclusion: The high-efficiency furnace saves nearly $10 for every million BTUs of heat delivered to the house.
Example 6: High Winter Propane Prices
Scenario: During a cold snap, the price of propane spikes to $4.75 per gallon.
1. Known Values: Price is $4.75. One gallon has ~91,500 BTUs.
2. Calculation:
Cost per MMBtu = ($4.75 / 91,500) * 1,000,000 = $51.91
Conclusion: At this price, propane's energy cost becomes almost as high as standard electric heat.
Example 7: Cheap Electricity (for Heat Pumps)
Scenario: A region with cheap hydropower has an electricity rate of $0.10 per kWh. This is relevant for high-efficiency heat pumps.
1. Known Values: Price is $0.10 per kWh. One kWh has 3,412 BTUs.
2. Calculation:
Cost per MMBtu = ($0.10 / 3,412) * 1,000,000 = $29.31
Conclusion: At this low rate, the raw cost of electric energy becomes competitive with heating oil and propane.
Example 8: Pre-Buy Heating Oil Contract
Scenario: A user signs a pre-buy contract for heating oil at $3.50 per gallon for the winter.
1. Known Values: Price is $3.50. One gallon has ~138,700 BTUs.
2. Calculation:
Cost per MMBtu = ($3.50 / 138,700) * 1,000,000 = $25.23
Conclusion: Securing a good price in the off-season leads to a competitive energy cost of $25.23 per MMBtu.
Example 9: High Natural Gas Prices
Scenario: Due to market volatility, the price of natural gas rises to $2.50 per Therm.
1. Known Values: Price is $2.50. One Therm has 100,000 BTUs.
2. Calculation:
Cost per MMBtu = ($2.50 / 100,000) * 1,000,000 = $25.00
Conclusion: Even at a higher price, natural gas remains a cost-effective option at $25.00 per MMBtu.
Example 10: Budgeting for Propane Tank Fill
Scenario: A user gets a quote for a propane fill at $2.85 per gallon and wants to compare its value.
1. Known Values: Price is $2.85. One gallon has ~91,500 BTUs.
2. Calculation:
Cost per MMBtu = ($2.85 / 91,500) * 1,000,000 = $31.15
Conclusion: The energy cost for this propane fill is $31.15 per MMBtu, providing a clear benchmark for budgeting.
Frequently Asked Questions about Fuel Cost
1. Why can't I just compare the price per gallon or kWh directly?
Because each unit contains a different amount of heat energy. A gallon of heating oil has about 50% more BTUs than a gallon of propane. Converting prices to a standard measure like "cost per Million BTUs" is the only way to make a fair comparison.
2. What is a "Therm" of Natural Gas?
A Therm is a unit of heat energy equal to exactly 100,000 BTUs. It's a common billing unit for natural gas companies, making the conversion to MMBtu very straightforward (10 Therms = 1 MMBtu).
3. Is a lower cost per MMBtu always the best choice?
It's the most important factor for fuel cost, but not the only one. You must also consider your heating system's efficiency (AFUE), maintenance costs, and the initial cost of installing a particular type of system. This calculator helps you master the fuel cost part of the equation.
4. How do high-efficiency heat pumps fit into this?
A heat pump doesn't create heat; it moves it. Its efficiency is measured by HSPF or COP and can be over 100% (often 200-400%). To compare, you would divide the electric cost per MMBtu by its efficiency (e.g., divide by 3.0 for 300% efficiency). A $50/MMBtu electric cost becomes a very competitive $16.67/MMBtu with a 300% efficient heat pump.
5. Where do I find my "Price Per Unit"?
Check your latest utility bill or fuel delivery invoice. For electricity, use the "total supply" or "generation" rate per kWh. For natural gas, find the price per Therm. For oil or propane, use the price per gallon from your last fill.
6. Are the BTU values used in the calculator exact?
The values are industry-standard averages for each fuel type. The exact BTU content can vary slightly by supplier and region, but these figures are highly reliable for making accurate cost comparisons.
7. Can I use this for other fuels like wood pellets or coal?
Not directly, but you can use the principle. Find the total BTUs in a unit (e.g., a ton of wood pellets has ~16.5 MMBtu). Then divide the price per unit by its MMBtu content. A $400 ton of pellets would cost $400 / 16.5 MMBtu = $24.24 per MMBtu.
8. Does this calculator work for cooling/air conditioning?
No, this is strictly for comparing the cost of heating. Air conditioning efficiency is measured by SEER or EER and is calculated differently.
9. Why is electricity often the most expensive option on this calculator?
The calculator shows the cost for electric resistance heating (like baseboards), where electricity is directly converted to heat at a 1:1 ratio. This process is less cost-effective than burning a fuel. High-efficiency heat pumps change this equation by moving existing heat instead of creating it.
10. How can I use this tool to save money?
Use it to confirm if your current fuel source is the most economical in your area. If you have options (e.g., oil vs. propane), it provides a clear answer. It also highlights the financial impact of price changes, which can motivate you to lock in a lower rate with a supplier or invest in a more efficient heating system.
