To determine essentially the most environment friendly technique to run our AC, we arrange two of the identical models (a 12,000-BTU model of the Midea U, our choose) on two totally different flooring of the identical residence constructing. We additionally took measurements from a 3rd residence, on a separate flooring, outfitted with a warmth pump (a now discontinued 18,000-BTU LG LAN180HYV3).
The warmth pump and one window unit have been in flats that have been roughly equal in measurement—about 1,200 sq. ft—with home windows going through south. The opposite Midea window unit went into a 3rd residence, on the highest flooring, and it was about two-thirds that measurement, with home windows going through west. The variations in elevation and daylight course would clearly have an effect on the take a look at outcomes, however I additionally thought it will be useful to check the power use in properties with totally different thermal envelopes beneath the identical climate situations. (Professional-tip: Insulation and weatherization make an enormous distinction!)
On the primary day of our exams, we shut the AC models off at midday, and we turned them again on at 5 p.m., after the solar had handed its apex over the constructing. We recorded the temperature inside every residence earlier than we turned the AC again on, after which we tracked how lengthy it took to get the indoor temperature again all the way down to 72 levels Fahrenheit.
The subsequent day, we did the identical factor—solely this time, we left the AC working all day at 72 levels. We used an power monitor to trace how a lot electrical energy every AC unit used over the course of every 24-hour interval.
On each days, the surface temperature reached a whopping 93 levels Fahrenheit.
To our shock, all three flats ended up utilizing extra power when the AC was turned off than after we left it working all day. The primary-floor unit, with the 18,000-BTU warmth pump, used 7 kWh of power on the day we turned off the AC, and it used solely 4 kWh after we left it working. Utilizing the typical electrical energy charge in Massachusetts, this is able to be a price distinction of about 44¢ per day.
Equally, the second-floor residence, with a 12,000-BTU window AC unit, used 18 kWh after we turned the AC off and 12 kWh after we saved it on—a value distinction of about $1.27 per day.
The westward-facing unit within the third-floor residence—which was smaller than the opposite two flats but in addition a greater measurement for its 12,000-BTU window AC unit—noticed the smallest change in power use: 12 kWh on the primary day with the AC unit off and 11 kWh when the unit was saved working. That may appear to be a small distinction, nevertheless it might nonetheless prevent about 20¢ per day.
This take a look at not solely confirmed us save power but in addition hold our properties extra snug. On the day we turned the AC models off, the temperature inside every residence bought up into the low 80s; even after we turned the AC models again on, it nonetheless took one other 90 minutes to chill the flats again down once more. In truth, solely the residence with the 18,000-BTU warmth pump was capable of get all the way in which again all the way down to 72 levels Fahrenheit earlier than sundown. In contrast, the temperature within the two flats with window AC models hovered round 75 levels till a number of hours after darkish, when the ambient temperature outdoors dipped as nicely.
In the event you’re going to have to attend that lengthy to chill your house again down after shutting off the AC, you shouldn’t additionally should take care of the upper utility payments that come together with it. Positive, you may have the ability to schedule the unit to show again on with sufficient time to chill your house again down earlier than your return. However then you must do extra work, and it’s nonetheless going to price you extra money than in case you had simply saved the AC working within the first place.
