In most residential and commercial buildings, air conditioning system accounts for one of the largest share of energy consumption. The share only goes higher during summers when it comes to maintaining a more comfortable indoor temperature. To put things in perspective, a study by US EIA found that around 17% of home electricity expenses are due to air conditioning, and this figure rises to about 27% in humid areas.
The energy expenses can rise even higher if the air conditioning systems are inefficient or old. With regular inspections and implementing energy efficiency measures, the air conditioning system can save up to 50% of the total energy costs.
There are several ways to reduce the cooling costs, and these measures can vary as each HVAC design is unique. However, there are 3 main strategies that are highly effective for almost every HVAC design –
- Upgrading to more efficiency units
- Improving building envelope
- Using smart controls
The demand for AC system installation and maintenance is higher in summer, which is why starting the AC system upgradation project before summer is the best recommendation.
Tip #1 – Upgrading to a More Efficient Air Conditioning Unit
Among the several ways to reduce the cooling costs, probably the most effective one in achieving the highest savings is upgrading the main HVAC equipment. Simply by replacing an old window-type air conditioner with an efficiency mini-split unit, you can achieve energy saving of over 70%.
Before you jump into fully upgrading the AC equipment, there are 2 important things to keep in mind:
- To have an accurate project budget to avoid dealing with unexpected expenses during the upgradation.
- Plan well in advance, so the new AC unit is operational when the summer arrives.
It is important to understand the energy efficiency metrics on the AC equipment as they give a general idea of energy savings. As the energy efficiency ratings increases, the cooling costs decreases. For instance, a SEER 26 mini-split consumes half of the energy as required for a SEER 13 unit.
Depending upon the type of AC equipment, these energy efficiency metrics change. For example:
- Unitary split system uses the Seasonal Energy Efficiency Ratio (SEER)
- Packaged rooftop units use Integrated Energy Efficiency Ratio (IEER)
- Chiller plants use kilowatts of electricity per ton of cooling (kW/ton)
Only in the case of kW/ton in chiller plants, a lower numerical value means higher efficiency. A 0.7 kW/ton means 30% less energy consumption than 1kW/ton
Tip #2 – Using Smart Controls for AC Systems
One of the most common issues found in most buildings is the inefficient use of air conditioners. A running air conditioner wastes energy, regardless of its efficiency, when the building does not need cooling. Similarly, energy is wasted in full cooling capacity with only partial building occupancy.
Smart thermostats can be used to automate smaller AC systems, while large commercial systems need building controls. However, some modern chillers come with built-in automation features, and additional controls are only required for components like hydronic pumps and air handlers.
Depending upon the building features, AC needs and local weather, the exact saving from smart AC controls may vary. However, as a rule of thumb, the US Department of Energy says that setting the thermostat by 7 degree Fahrenheit to 10 degree Fahrenheit for 8 hours/day will reduce the HVAC costs by 10%.
Tip #2 – Efficient Building Envelope
Even when the indoor spaces are in ideal conditions, heat can still move in and out of the building if the building envelope is inefficient. There are mainly 2 ways the uncontrolled heat can move in and out of the building:
- Heat conduction on surfaces with low insulation. These surfaces can be walls, floors, roofs, basements, etc.
- Air leakage between the interior and exterior of the building, or between conditioned or unconditioned spaces.
Fortunately, there are simple ways to improve the building envelope and avoid disruption, such as adding spray foam insulation and caulking. On the other hand, a deep energy retrofit project can achieve major improvement of the R-value. However, this type of project is more disruptive and capital intensive. An efficient building envelope saves energy all year long, since it helps both space heating and air conditioning systems.
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