Back to Chart


About the Fuel Efficiency Comparison Chart  

1. What information is in these fuel-efficiency comparison charts?
2. What type of heat do you like?
3. How do I use the information in these charts?
4. Should I simply go with the fuel that costs less? What else should I consider?
5. Do I want my house to feel warm or room temperature in the winter?
6. Why are the costs of fuel converted to costs per million BTUs?
7. Why are the "efficiencies" of heating appliances different? Why don't I just use the differences in fuel costs to make comparisons?

What information is in these fuel-efficiency comparison charts?
These comparisons apply only to heating appliances: space heating and water heating. The costs shown here are the costs of fuel (natural gas, electricity, heating oil and propane) used by heating appliances to create heat. Therefore, this is a comparison of 'operating costs,' or 'heating costs.' These costs play the largest role in the way your bills vary from month to month and season to season.

These comparisons do not include the costs of equipment or installation of appliances. They also do not include service fees, delivery charges and other "flat" fees that may be charged by your utility or fuel supplier. Those costs also need to be compared (by talking with your appliance salesperson, utility representative or building contractor) when making a decision about space heating and water heating appliances.

What type of heat do you like?
In addition to comparing costs of fuels and appliances, it is also very important that you consider the type of heat you like. Natural gas, propane and fuel oil are all used for the types of furnaces that basically use a flame to blow hot air through your ducts. If you set your thermostat at 74 degrees, the air from these fuel-burning systems will be blown at temperatures much higher than 74 degrees, to quickly raise your home's temperature to that setting. Whenever your home's temperature drops below 74, the furnace burns more fuel and blows more hot air.

If cost efficiency and environmental friendliness are more important to you than instant heat, a heat pump or geothermal system should be included in your considerations as a comfortable alternative to fossil fuels. These highly efficient electric-energy systems pull warmth from the earth or atmosphere and transfer that warmth into your home - bringing your temperature up to your desired temperature, and maintaining it. Therefore, these electric systems don't blow air at temperatures much higher than your desired setting. When the winter weather remains at a low temperature for several consecutive days, the electric systems may use electric "heat strips" to blow hotter air into the home. These heat-strip cycles are less energy efficient, and can be used less by 'dialing-down' the temperature a couple of degrees. Over the course of the average winter in Kentucky, the regular cycles of these systems are very efficient if the heat strips are not used excessively.

Comparing the costs of both types of systems depends largely on the fluctuating costs of heating fuels (natural gas, propane and fuel oil). The price of electricity remains more stable. When fuel prices are low, the fuel-burning systems are competitive with electric-system heating costs. When fuel prices are high, the electric systems will likely cost less to operate. Refer to the "high-efficiency" comparison chart to see how the heating costs compare at current prices. It is because of these fluctuations that you should consider what type of heat you prefer.

How Do I Use The Information in These Charts?
In the "space heating" and "water heating" charts, simply use the differences in the operating costs per 1,000,000 BTUs to gain some insight into which fuels cost more or less for the various types of appliances. If one type of fuel or energy costs twice as much as another for standard space heating, you can expect the heating bills to be noticeably higher. If the costs are very similar, the difference won't be as noticeable in your monthly bills.

Note: It is most important to look at the "efficiency ratings" of the heating appliances you are comparing. As you can see, we have applied average efficiencies of different types of appliances. These averages are not exact. Ask your appliance salesperson to tell you about the efficiency ratings of the appliances you are considering.

It might be a good idea to print out our fuel-efficiency comparison page, and bring it with you to your appliance dealer. Your salesperson will likely be able to calculate wintertime heating costs using our fuel costs in BTUs.

Should I just go with the fuel that costs less? What else should I consider?
It may be that fuel "A" costs less than fuel "B," but if the cost of the appliance (and installation of the appliance) for fuel "A" is much higher than the appliance for fuel "B," it might take you a few years to make up the difference in savings with lower heating bills. As you can imagine, you may find yourself asking how long you plan on being in your home. As a general rule of thumb, the high-efficiency heating system will cost you more up front, compared to a low-cost, low-efficiency furnace, but your wintertime heating bills will be lower with high-efficiency systems.

Do I Want My House to Feel Warm or Room Temperature in the Winter?
In addition to comparing costs of fuels and appliances, it is also very important that you consider the type of heat you like. If you need to feel hot air blasting out of your heating registers, you definitely won't want an electric heat pump or geothermal system. Natural gas, propane and fuel oil are all used for the types of furnaces that blow hot air through your ducts. If you only want to feel comfortable in the winter, and cost efficiency is more important to you, a heat pump or geothermal system should be included in your considerations. These highly efficient electric-energy systems pull warmth from the earth or atmosphere and deliver that warmth (not necessarily "heat") into your home - basically making your home "room temperature" comfortable.

Why Are the Costs of Fuel Converted to Costs Per Million BTUs?
In order to provide an 'apples-to-apples' comparison of fuel costs, their units of measurement must be the same. Natural gas, electricity, propane and fuel oil are all measured differently: cubic feet (cf) of natural gas; kilowatt hours (kWh) of electricity; gallons of propane; and gallons (gal) of fuel oil. Therefore, the units of measurement must be expressed as BTUs (British Thermal Units), the universal measurement of expended energy, also known simply as "heat." By showing all of the fuel costs for the same amount of BTUs, we have the apples-to-apples comparison of the different types of fuel.

When you shop for heating appliances, they typically include their BTU output, and possibly the number of BTUs that are output in a winter, or in a year.

Why are the "efficiencies" of heating appliances different? Why don't I just use the differences in fuel costs to make comparisons?
When comparing operating costs of heating appliances, it is important to make adjustments for their differences in 'operating efficiency.' If a space heater is 70% efficient, it means that 70% of your purchased fuel or electricity is actually being converted into space heat. The other 30% provides the energy that is needed in the process of burning the fuel or converting electricity into space heat. In water heaters, 90% efficiency would mean that 90% of the heat is actually being applied to the water; the other 10% would be "lost" through the walls of the water heater.

Therefore, different appliances don't burn BTUs at the same rate to achieve the same heating temperature that you desire. The cost per BTU must be applied to the efficiency ratings of the various appliances to estimate costs of running those appliances.

Back to Chart