Question: I currently have an RTU installed but I’m convinced I could be saving more on energy bills without replacing my unit. What can I do?

Answer: While RTUs aren’t generally considered energy-efficient, so much progress has been made that nowadays there’s a lot you can do to improve the efficiency of existing units! Take a look!

What is an RTU?

Rooftop Unit air conditioning units, or RTUs, are packaged rooftop units, used predominantly in small 1-2 story commercial or institutional buildings. RTUs, which are perfect for restaurants, office buildings, retail stores and motels,  are commonly located on rooftops but can be installed on a concrete pad at ground level and typically include a blower section, filter bank, evaporator coil and at least one compressor.

According to a fact sheet published by the City of Anaheim, RTUs are generally considered inefficient because they use air-cooled condensers, high-pressure-loss filters and cooling coils, inefficient fans with poor aerodynamics, and control strategies that miss energy-saving opportunities. That being said, in today’s world, there are many options to upgrade, retrofit or invest in new technologies that can make your RTU much more energy-efficient and save you a lot of money in the process.

A new era of RTU products and optimizers

ENERGY STAR suggests that efficiency levels for RTUs have been on a steady increase over the course of the past 15 years. The number of smaller models with an EER (energy efficiency ratio) of at least 10.4 grew from 14% to 65% between 1993 and 2007.

Today, units this size have EERs as high as 12.7, meaning that upgrading to a newer model can produce serious long-term savings (for a list of units that meet ENERGY STAR program criteria, visit the EPA website). If your unit is older than 15 years (the approximate lifetime of a RTU), it’s time to re-invest in a more energy-efficient unit that will reduce the risk of mechanical failure and save you money all year round.

What makes new RTUs so much more efficient?

High-efficiency RTUs may be costly, but they offer a payback of as little as 2 years; not very long if you’re in the business to save big time on energy costs. What exactly makes the newer models more efficient? According to Touch Stone Energy, newer models have factory installed microprocessors or controls, like scheduling and lockout controls, that reduce energy consumption of the overall systems while maintaining comfortable conditions in the building. These controls can turn the unit on or off depending on the time of day, or adapt to outside air conditions, while lockouts can override schedules and keep a unit off when, for example, parts of building remain unoccupied.

Newer units also allow for a communication interface that enables users to connect them to energy-management systems or demand-controlled ventilation systems. Some manufacturers have started to apply variable volume capabilities to newer RTUs that match the airflows to the different loads in different spaces, using variable speed drives to supply varied airflows which decrease energy use.

Read more about economizers that can help you save on costs and decrease the wear and tear on your air-conditioning unit on the Office of Energy-Efficiency website, via Natural Resources Canada.

Questions or comments about high-efficiency RTUs? Leave them below!

image credit: jaricacandheatingcompany