If a detailed energy analysis is performed for a residential or commercial building, the largest load will normally be space heating or air conditioning. Most air conditioning systems use electricity, except in specific cases where another energy source is viable. However, space heating equipment uses a wider variety of fuels. Heating costs can be reduced by upgrading to more efficient units, but changing the energy source is also effective in many cases.


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Before any space heating upgrade, energy consultants recommend a building envelope inspection. A building with deficient insulation or plenty of air leaks is more difficult and expensive to heat. This applies even when using a modern boiler or heat pump with a high nameplate efficiency. If the building envelope is improved first, the new heating system can be specified with both a higher efficiency and a smaller capacity. Consider that an efficient thermal envelope saves on air conditioning as well.

Finding the Optimal Space Heating Option for Each Building

Since there are various energy sources for space heating, there are also many types of equipment. The metric used to describe efficiency changes depending on the equipment type:

  • The Annual Fuel Utilization Efficiency (AFUE) is used by furnaces and boilers, and it describes how efficiently they convert fuel energy into building heat. AFUE values above 90% are typical with modern high-efficiency units, while older furnaces and boilers may fall below 60%.
  • The Heating Seasonal Performance Factor (HSPF) is used by air-source heat pumps. These devices use the same principle as air conditioners, but in reverse - thermal energy is extracted from the outdoor air, and supplied indoors as heat. Generally, an HSPF value above 8 is considered good, while the best heat pumps have an HSPF above 10.
  • Ground-source heat pumps don’t have a dedicated metric to describe their efficiency, and they typically use the Coefficient of Performance (COP), which is a ratio of heat output and electricity input. These heat pumps normally have COP values above 3, and the most efficient units reach COP values up to 6.

Electric resistance heaters convert all their electricity input into heat, which means they technically have 100% efficiency. However, this value can be misleading, since resistance heaters are very expensive to operate. Air-source heat pumps normally use over 50% less energy than resistance heaters, while ground-source heat pumps use over 70% less.

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For buildings with combustion heating, a simple measure is upgrading to equipment with a higher AFUE. On the other hand, properties with resistance heating can achieve significant savings with heat pumps. Variable refrigerant flow (VRF) systems operate at high efficiency using heat pump technology, and they can be used for both heating and cooling.

Ground-source heat pumps have the highest efficiency among the electrical heating options, but they also come with a high upfront investment. Since these heat pumps have underground components, they are easier to install in new constructions.

To identify the heating system that offers the highest return on investment in your building, the best recommendation is getting an assessment from a qualified HVAC engineering firm.

Should You Change the Energy Source of Your Heating System?

If you are considering a change of energy source, there are both economic and environmental factors involved. For example, fuel oil produces twice as much emissions and natural gas for a given heating load. Switching to natural gas also simplifies operation, since gas is delivered as a utility service, while heating oil must be distributed by truck and stored locally.

  • A change from combustion heating to electric heating reduces the local emissions from your building.
  • There will still be off-site emissions if the local power grid uses fossil fuels, but moving emissions from buildings to power plants helps reduce urban pollution.
  • When heating systems become electric, the transition to clean energy sources is also simpler. They automatically become greener if the grid starts using more clean energy.

Since electric heating is generally more expensive than combustion heating, you must use the most efficient options to avoid paying more for heating. Ground-source heat pumps and the most efficiency VRF systems can compete with the heating cost of natural gas, while eliminating site emissions.

 

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