Heating Systems


Heating Systems Stave off Winter’s Bite for Cuddy Comfort

Here’s a list of common types of heating systems, plus related information and terms:

Furnaces and Boilers

Furnaces and boilers are used to heat buildings. They may be fueled by electrical resistance, gas, oil, or coal. A furnaces and boilers are the most commonly heating devices.

Wood and Pellet-Fuel Heating

Wood and pellet-fuel heating provide heat by using biomass or waste sources for fuel.

Electric Resistance Heating

Electric resistance heating uses electricity to create heat. It is among the most expensive and least efficient means to heat a home.

Active Solar Heating

Active solar heating uses sunlight to heat air or liquid as a supplemental source of heat.

Radiant Heating

Radiant heat provides heating to a floor, wall or ceiling.

Small Space Heaters

A small space heater is a unit that may save energy when heating a small space.

Heat Distribution Systems

Heat may be distributed throughout your home in a variety of ways. Forced-air systems are most common, usually paired with central air conditioning. More passive radiant systems such as heat pumps, radiant heating, steam radiators or hot water radiators may be used.

When is it time to replace?

Beware of the following signs that your system may need to be replaced. Staff from Plumbing and Heating by Craig will help you evaluate the safety and effectiveness of your heating and cooling systems across system lifespan.

Indications It’s Time to Assess Your System
  • Your system has been in service for ten years old, or longer.
  • Your equipment needs frequent repairs and your energy bills are going up.
  • Your rooms are not consistently cool or warm enough.
  • Your home has problems with humidity.
  • Your home is excessively dusty.
  • Your heating or cooling system is too noisy.
ACCA Information Sheet about the 2007 Energy Bill: Selecting Heating Fuel & System Types

When it is time to choose a heating system for your home, a detailed analysis is required to optimize the selection. A specialist from Plumbing and Heating by Craig is available to help you, if you prefer. The following list of details must be considered:

  • Price and availability of the energy source or fuel.
  • Equipment used to convert fuel to heat.
  • Method used to distribute heat throughout your home.
  • Cost to install, purchase, and maintain the heating equipment – total cost of ownership across lifespan.
  • Efficiency of the equipment and system.
  • Environmental impacts.

Most homeowners are limited in their options for heating fuels. In the Northeast, the main options are fuel oil or electricity, and sometimes natural gas. In rural areas, propane or wood are common choices. Elsewhere, natural gas and electricity are the main options.

Solar energy now is available, and passive solar heating may be effective in moderate climates. Active solar heating systems often are considered a supplemental heating source, and are usually compatible with other heating systems. Solar air heating can be used as a method of preheating, as a boost for heat pumps, or as a supplement to hot water heating systems.

Pellet-fuels are also available now, as well as wood and propane.

One way to evaluate heating options is to compare the cost of the fuel. Useful information in making these calculations includes the energy content of fuel and its efficiency as it converts to heat.

Fuels are measured in physical units (gallons of oil or propane, cubic feet of natural gas, or kilowatt hours of electricity (kWh); or by heat content. In the United States, the most commonly used unit for expressing the relative energy value or heat content of a fuel is the British thermal unit (Btu). One Btu is the amount of energy needed to raise the temperature of one pound of water 1°F, when water is at about 39°F. One “therm” is 100,000 Btus.

The table below provides a list of typical heating fuels and the Btu content in the units in which they are typically sold in the United States. The figures below are general references for residential heating applications only. Commercial and industrial users should obtain more precise values from their fuel vendors.

Table 1: Average Btu Content of Common Fuels
Fuel Type
Output of Btus per Unit
Fuel Oil (No.2) 140,000/gallon
Electricity 3,412/kWh
Natural Gas 1,025,000/thousand cubic feet
Propane 91,330/gallon
Wood (air dried)* 20,000,000/cord or 8,000/pound
Pellets (for pellet stoves; premium) 16,500,000/ton
Kerosene 135,000/gallon
Coal 28,000,000/ton

The efficiency of the heating appliance is an important factor for determining the cost of a given amount of heat. In general, the efficiency is determined by measuring how effectively an appliance turns fuel into useful heat.

Table 2: Estimated Average Fuel Conversion Efficiency of Common Heating Appliances
Fuel Type – Heating Equipment Efficiency (%)

Coal (bituminous)

Central heating, hand-fired 45.0
Central heating, stoker-fired 60.0
Water heating, pot stove (50 gal.) 14.5


High efficiency central heating 89.0
Typical central heating 80.0
Water heater (50 gal.) 59.5


High efficiency central furnace 97.0
Typical central boiler 85.0
Minimum efficiency central furnace 78.0
Room heater, unvented 99.0
Room heater, vented 65.0
Water heater (50 gal.) 62.0


Baseboard, resistance 99.0
Central heating, forced air 97.0
Central heating, heat pump 200+
Ground source heat pump 300+
Water heaters (50 gal.) 97.0

Wood & Pellets

Franklin stoves 30.0 – 40.0
Stoves with circulating fans 40.0 – 70.0
Catalytic stoves 65.0 – 75.0
Pellet stoves 85.0 – 90.0

The costs of fuels can be determined by researching your utility bills or fuel suppliers. The DOE’s Energy Information Administration may be another good source of information.

In addition to cost, you might consider the environmental impact of your heating fuel. You probably generate more greenhouse gases by maintaining the temperature in your home than by any other activity.

Most electricity in the United States is generated by burning coal, which emits sulfur dioxide, nitrous oxides, particulates, and greenhouse gases. This is not a clean energy source. Some electricity is generated from natural gas, which burns cleaner, but more than half of the energy is lost in converting and delivering electricity.

Electricity is used to run heat pumps, which have the benefit of producing more energy than they consume. An electric heat pump system can offset efficiency losses at the power plant by using the electricity to draw energy from the outside environment.

Burning natural gas, oil, propane, wood, or pellets in your home with a high-efficiency furnace or boiler can be an efficient way to deliver heat to your home; natural gas burns cleanest.

The cleanest and most environmentally-friendly fuel for heating, (and possibly cooling) your home is solar energy. In most homes, solar energy is a supplement to a primary system, especially in harsh climate environments.

Not every heating and cooling system is a good fit for every application. Selecting a system should be based on fuel types that are readily available, your personal preferences, and the following considerations:

  • Do you want a central air conditioning system? If so, you may find it useful to determine whether heat pump options, particularly geothermal heat pumps, would be practical for your home?
  • Don’t want central air conditioning? Could a baseboard hot water system or a radiant heating system meet your needs?
  • Would a room air conditioner, an evaporative cooler, or a ductless mini-split system work for you?
  • Are you interested to evaluate a solar energy option?

Answering these questions, and exploring the information in the heating, cooling, and heat pump sections of this web site, can help you determine your best option.

Gas-fired Boilers and Furnaces

Gas furnaces and boilers are fueled by natural gas or propane. Propane is widely available, but usually more expensive. Natural gas requires a distribution system in your area, and some regions experience higher costs.

While retrofitting may be possible for gas-fired furnaces and boilers, a cost/benefit ratio should be considered. Below are possible retrofit options.

Vent dampers

The addition of a vent (or flue) damper is common. A vent damper prevents chimney losses by closing off a boiler’s vent when the boiler isn’t firing. Bigger boilers and steam boilers benefit from vent dampers more than hot-water boilers or small boilers.

Intermittent ignition devices

Older furnaces and boilers with a continuous pilot light can be retrofitted with intermittent ignition devices. The difficulty of installation requires a professional at a cost of about $250 with a payback of less than 10 years. These devices are not always cost-effective on older equipment, so you might consider turning off the pilot light on the stove for the summer.

Derating gas burners

Boilers and furnaces today are often too big, and sometimes the heating capacity can be reduced. Talk to your HVAC professional about your options. A modulating aquastat for the hot water in the boiler can save money and energy also, or you can adjust the aquastat down during summer.

Time-Delay Relay (for hot water boilers only)

A time-delay relay is a way to access the most heat from your heating system, the boiler. When the thermostat clicks on, the relay causes the boiler to circulate hot water through the system, keeping the boiler operation on hold until later.

Oil-fired Boilers and Furnaces

Oil-fired furnaces and boilers can use renewable fuels for heating. Many companies now offer heating oil combined with bio-diesel. This enables customers to reduce their dependence on foreign oil and access domestic energy. The bio-diesel blends are better for the environment than pure heating oil.

Retrofits are possible for oil-fired furnaces and boilers, but the benefit of new equipment may also be considered. The following retrofits are possible for these types of heating units:

Vent dampers

The most common retrofit is the addition of a vent (flue) damper. A vent damper prevents chimney heat losses by closing off a boiler’s vent when the boiler isn’t firing. Steam boilers benefit from vent dampers more than hot-water boilers, and bigger boilers benefit more than smaller ones. Vent dampers, however, may not be cost effective with properly sized, newer furnace models. For older oil burners, converting to a flame retention burner (below) is probably a better investment.

Barometric flue damper

Ask for a draft test during your annual system check-up. If too much heat is escaping through the chimney, you may need to install a barometric flue damper. The cost is less than $100 and could save you about 5% of your fuel cost.

Derating or replacing oil burners

Many boilers and furnaces in today’s homes are oversized, particularly if you’ve enhanced the energy efficiency of your home. One simple fix to reduce the heating capacity of your oil boiler or furnace to make it operate more efficiently is by having a technician install a smaller nozzle.

Modulating Aquastats (for hot water boilers only)

An aquastat controls the temperature of the hot water in a boiler, typically holding the temperature to about 180°F. But, when during seasons when heating needs are lighter, such as in the spring and fall, a lower temperature setting will save fuel and costs without impacting comfort. A modulating aquastat, also called an outdoor reset, senses outdoor temperatures and adjusts the hot water temperature accordingly. The units can save as much as 10% of fuel costs for a relatively low investment price. You also can manually adjust your aquastat to 120°F during the summer.

Comparing heating fuels

Comparing the price of heating fuels is an important part of selecting a heating system. Fuels are measured and sold in different units, such as gallons of oil, therms of natural gas, or kilowatt hours (kWh) of electricity. Standardizing cost-efficiencies for different fuels can help you identify your best overall option.

Since it is difficult to compare price across units (therms versus gallons versus kilowatt hours), a more useful comparison is the fuel cost per amount of heat produced. EIA’s Heating Fuel Comparison Calculator helps you make this comparison. It factors in the relative price based on the fuel heat content and the heating appliance’s efficiency. The Comparison Calculator provides instructions, including how to find cost and efficiency data to use with the Calculator. The Calculator is a Microsoft Excel spreadsheet. You can use it online or save it to your hard drive and then open it in your Excel software, if you have it installed on your computer.

A Plumbing and Heating by Craig specialist is available to help you with these calculations, and any other heating and cooling questions you may have. The choices you make today will impact your future comfort and costs. Ask us for help.