It’s very simple. With ducted or ductless mini-split systems, you only pay for and use as much or as little heating and cooling as you need at any given time in any given room? How does it work?

Technically, it has everything to do with something called an inverter-driven scroll compressor that is inside the outdoor unit (a.k.a. condenser, compressor).

Practically, it’s like a pay-as-you-go cell phone. You only pay for the minutes you use every month, no more, no less.


How does it work? The high-tech modulating compressor (inverter-driven scroll compressor) in the guts of the outdoor equipment adjusts the amount of electricity and refrigerant (the hot and cold liquid that is used to condition the house) to deliver exactly the amount of heating and cooling needed at any given time in any given room. If you only need a little bit in your Master Bedroom at 1 o’clock in the afternoon, it will power up just enough to give you that little bit.

That hot and cold refrigerant is then sent from that compressor to small air handlers (indoor fan coils) that are strategically placed inside and throughout the house to deliver exactly the amount of hot and cold air that each room needs. What determines those needs is the dedicated controller (thermostat) in that room that the owner sets to maintain a certain temperature (and check out the awesome one in our “One bad a$$ thermostat” farther down the blog page).

So, instead of a central air handler delivering a LOT of air, it’s like a bunch of tiny air handlers delivering small amounts of air wherever and whenever it’s needed.The air handlers can have ductwork and be concealed in a ceiling, attic or floor cavity to serve up to three or four rooms. OR, they can deliver the air without ducts with wall-mounted or recessed (in wall/ceiling) ductless units (check out the attached images). Either way, these air handlers deliver air with a fan that is generally quieter than a human whisper.

Why variable makes sense: Everything about these systems is variable, efficient, quiet, great for indoor air quality, and extremely effective.

Contrary to much thinking, these systems can and do work in all climate zones. They’ve been used in Europe, Asia, Canada, and South America for decades, and have proven themselves to be reliable. HVAC companies rave about how few call backs and/or repairs that there are with these systems and how long they last.

Generally, they are at least 30% more efficient than conventional systems. Their official efficiency ratings (where above 16 is considered good) range from 16 – 26 SEER at full capacity, but they rarely run at full capacity (lower capacity allows for higher efficiency). So, real world SEER values are in the high 20′s, and low 30′s.

In regards to power consumption, outdoor units (heat pump or air conditioner) draw about 25-40 amps of electricity when in use. The maximum amp draw on a residential mini-split outdoor unit is 18 amps. Again, because of the variability, and the fact that the system is never on full capacity, the amp draw is usually much lower…maybe around 10 amps or possibly less.

The linked graph shows just one of the many ways that the mini-split systems are better at minimizing energy use and why these need to become more commonplace than the power hungry massive systems we so easily drop into our lives and outside our homes.