In most homes and commercial buildings, the air conditioning system is responsible for the largest share of energy consumption in summer. The electricity costs are even higher when AC units are old and inefficient, or when buildings have poor insulation and air leakage issues. However, there are many energy efficiency measures that can reduce your cooling costs.

Each HVAC design is unique, but there are three main strategies to reduce air conditioning costs: upgrading to more efficient units, improving the building envelope, and using smart controls. 

• A more efficient air conditioner consumes less electricity for a given cooling load.
• A well insulated and airtight building envelope keeps the summer heat outside more effectively, reducing the workload on AC systems.
• Smart controls ensure that air conditioning only runs when needed, optimizing energy consumption.

When these three measures are deployed together, you can achieve the lowest possible cooling cost for a building.

Upgrade your air conditioning system and reduce your power bills during summer.

If you plan to upgrade your air conditioning systems, the best recommendation is starting your project before summer. When the warmer months arrive, the demand for installation and maintenance services is higher. Also, your AC system must stop operating while being upgraded, which causes discomfort for building occupants.

Tip #1 - Upgrading to a More Efficient Air Conditioning Unit 

There are many ways to reduce cooling costs in a building. However, you will probably achieve the highest dollar savings by upgrading the main HVAC equipment. For example, if you replace an old window-type air conditioner with a modern and efficient mini-split unit, you will likely achieve energy savings of over 70%.

There are two important things to keep in mind if you are planning a full upgrade of your air conditioning equipment:

• Make sure you have an accurate project budget, so you don’t have to deal with unexpected expenses during the AC upgrade.
• Plan your project well in advance, so you already have the new AC unit operational when the summer months arrive.

Energy efficiency metrics change depending on the type of AC equipment you are dealing with. Unitary split systems use the Seasonal Energy Efficiency Ratio (SEER), packaged rooftop units often use the Integrated Energy Efficiency Ratio (IEER), and chiller plants use kilowatts of electricity per ton of cooling (kW/ton). You may also find metrics like the Coefficient of Performance (COP) or Energy Efficiency Ratio (EER), which are not for a specific type of equipment.

In general, cooling costs decrease as the numerical value of the efficiency rating increases. For example, a SEER 26 mini-split has half the energy consumption of a SEER 13 unit. The main exception is for kW/ton in chiller plants, where a lower numerical value means a higher efficiency. For example, 0.7 kW/ton means 30% less energy consumption than 1 kW/ton.

Tip #2 - Using Smart Controls for Air Conditioning Systems 

When a building does not need cooling, a running air conditioner is a waste of energy regardless of its efficiency. However, there is also energy waste when the full cooling capacity is used with partial occupancy. Unfortunately, this is very common in buildings, and many AC systems run at full output without considering the actual cooling needs.

For example, a space cooling system may be required to run at full capacity on a hot summer day when the building is full. However, this is not necessary if a building is partially full on a day earlier in the summer, before the maximum temperatures arrive.

Smaller air conditioning systems can be automated with smart thermostats, while larger commercial systems will 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.

The exact savings from smart AC controls will vary depending on building features and the local weather. However, the US Department of Energy provides a useful rule of thumb: setting back the thermostat 7-10°F by 8 hours/day will reduce your HVAC costs by 10%.

Tip #3 - Keeping Heat Outside with an Efficient Building Envelope

Uncontrolled heat movement into and out of a building represents a waste of energy, and there are two main ways in which this can happen:

• Heat conduction through surfaces with low insulation. These can be walls, roofs, floors, basements, attics, etc.
• Air leakage between the building interior and exterior, or between conditioned and unconditioned spaces.

There are simple ways to improve a building envelope with minimal disruption, such as adding spray foam insulation and caulking. On the other hand, you can achieve a major improvement of the R-value with a deep energy retrofit project. 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.