Cubic Feet to kWh Calculator: Gas & Heat
The calculator for this page is switched off while it is checked. The formula is below, and the worked example in the article shows how to use it by hand.
This calculator converts a volume of natural gas in cubic feet (or cubic meters) into the equivalent energy in kilowatt-hours (kWh). You enter the gas volume and, if needed, the energy content of your specific gas supply, and the calculator returns the energy in kWh. The result uses the standard formula for energy conversion based on the gas’s heating value.
Formula
The conversion relies on a single energy equivalence: 1 kWh = 3,412.14 British Thermal Units (BTU). The formula is:
Energy (kWh) = (Volume × Heating Value) ÷ 3,412.14
- Volume – the amount of gas, in cubic feet (ft³) or cubic meters (m³). If you enter cubic meters, the calculator multiplies by 35.3147 to convert to cubic feet.
- Heating Value – the energy released by burning one cubic foot of gas, typically in BTU/ft³. Natural gas in the U.S. averages about 1,030 BTU/ft³, but it can vary between 950 and 1,150 BTU/ft³ depending on the gas composition and source.
- 3,412.14 – the exact number of BTU in one kilowatt-hour.
The result is the gross (higher) heating value. Some appliances use the lower heating value, which is about 10% less, but for billing and general conversion, the higher value is standard.
Worked Example
Using the default inputs from the calculator above:
- Gas volume = 100 ft³
- Heating value = 1,030 BTU/ft³
First, calculate the total BTU:
100 ft³ × 1,030 BTU/ft³ = 103,000 BTU
Now convert BTU to kWh:
103,000 BTU ÷ 3,412.14 = 30.19 kWh
The calculator shows 30.19 kWh (rounded to two decimals). If you used cubic meters instead, you would first multiply by 35.3147 to get cubic feet, then apply the same steps.
Why Convert Cubic Feet to kWh?
This conversion is most useful for understanding natural gas bills. In the U.S., gas is often billed in “therms� (100,000 BTU) or “CCF� (100 cubic feet). In many other countries, energy is billed in kWh. If you have a meter reading in cubic feet but your bill or appliance specs are in kWh, this calculator bridges the gap.
It also helps when comparing the cost of gas vs. electricity for heating, cooking, or drying. For example, a gas oven might use 10,000 BTU per hour; converting that to kWh (about 2.93 kWh) lets you compare it to an electric oven’s wattage.
How to Use the Calculator Correctly
- Enter the gas volume – read your meter or the appliance spec. Be sure to note the unit (ft³ or m³).
- Select the unit – if you enter cubic meters, the calculator converts to cubic feet automatically.
- Adjust the heating value – if you know your gas supplier’s specific BTU/ft³, enter it. Otherwise, leave the default of 1,030.
- Read the result – the first output is the energy in kWh. That’s the number you need for comparisons or billing.
Common Mistakes and How to Avoid Them
- Mixing units – A cubic meter is about 35.3 cubic feet. Entering 1 m³ as 1 ft³ would give an answer 35 times too small. Always check the unit selector.
- Using the wrong heating value – The heating value of natural gas can range from 950 to 1,150 BTU/ft³. Using 1,030 is fine for most purposes, but for precise billing, use the value on your gas bill or supplier’s website.
- Ignoring the difference between higher and lower heating value – Condensing boilers and some turbines use the lower heating value (LHV), which excludes the latent heat of water vapor. LHV is roughly 10% lower than HHV. This calculator uses HHV, which is the standard for gas billing in most regions.
- Rounding too early – If you round the BTU conversion factor to 3,412, your result may be off by a few hundredths of a kWh. The calculator uses 3,412.14 for accuracy.
Limitations and Important Context
This calculator gives a theoretical energy equivalent. Real-world energy output depends on the appliance’s efficiency. A gas furnace might be 80% efficient, meaning only 80% of the energy in the gas becomes heat for your home. The kWh figure here is the energy content of the gas, not the useful heat delivered.
Also, gas volume can be affected by temperature and pressure. Utilities often correct meter readings to standard conditions (usually 60°F and 14.73 psi). If you are using a raw meter reading, the actual energy may differ slightly. For most residential and commercial comparisons, the uncorrected volume is sufficient.
Frequently Asked Questions
How many kWh are in 100 cubic feet of natural gas?
Using the average heating value of 1,030 BTU/ft³, 100 cubic feet contains about 30.19 kWh. If the heating value is higher, say 1,100 BTU/ft³, it would be about 32.24 kWh. The exact number depends on the gas composition.
What is the difference between a therm and a kWh?
A therm is 100,000 BTU. One kWh is 3,412.14 BTU. Therefore, 1 therm equals about 29.3 kWh. Gas bills in the U.S. often use therms, while electricity bills use kWh. This calculator can help you compare the two.
Can I use this for propane or other gases?
No, this calculator is designed for natural gas. Propane has a much higher heating value—about 2,516 BTU per cubic foot of gas vapor. If you need to convert propane, you would need a different calculator or adjust the heating value manually (though the calculator would still work if you enter the correct BTU/ft³).
Why does my gas bill show CCF instead of kWh?
CCF stands for “centum cubic feet,� which is 100 cubic feet. Many U.S. utilities bill in CCF or therms. If your bill shows CCF, multiply by 100 to get cubic feet, then use this calculator to convert to kWh. For example, 5 CCF = 500 ft³, which is about 151 kWh.
How do I convert kWh back to cubic feet?
To reverse the calculation, multiply the kWh by 3,412.14 to get BTU, then divide by the heating value (BTU/ft³). For example, 30 kWh × 3,412.14 = 102,364 BTU, divided by 1,030 = 99.4 ft³. This is the inverse of the formula used here.