I was hoping there may be some users out there with mini splits that have measured energy usage to give me some insight in to power consumption. I have 3 outdoor units(below) in a big historic home. My concern is around the 36k unit and it pulling more energy than the other 2 units combined (screenshot). I had a Tech out today and shared the data from my Iotawatt, he checked the int with his gear and ultimately told me that everything checks out and explained away the higher usage due to the unit is on the sunny side of the house along with the rooms it was cooling. Long story short just looking for some experience on if this usage checks out or am I right in being concerned that this unit uses way more power than my other units that can’t just be explained by being on the sunny side of the house. Appreciate any thoughts.
Bosch 3 ton heat pump with Bosch 36 BTU air handler. I’ve combined outdoor and handler in my screenshot
Mitsubishi hyper heat 24K unit with 2 12k heads
Mitsubishi hyper heat 36k unit with branch box and 3 12k heads
Looking up the specs for a Mitsubishi 3 ton unit, the maximum power usage when cooling is around 2,700 Watts, which is about what you are using at peak during three of the days. The sunny side reasoning seems reasonable. Eight tons of AC is a lot of cooling. This may be a glass-half-empty scenario. Consider if the other two units were also working to their max while on the cooler side of the house.
It looks like June 13-15 used quite a bit more than the other days. Were those days sunnier? The Bosch unit seemed to load up more on those days, but the other Mitsubishi doesn’t seem to be as sensitive to different conditions.
Turn off all the head units on the Mitsu 3 ton and observe how quickly the rooms warm up at the point in time on your graph where power consumption is approaching the peak (in similar weather conditions). If they become rather hot in a short amount of time, then the system load/power consumption makes sense and you have a large heat load to deal with. The sun beating on the condensing unit/outside unit is going to have a very minimal effect compared to the internal house heat load.
I would guess the windows are letting in a lot of radiant heat, and if so some thermal window film would help tremendously.
Thanks for the replies! I wasn’t necessarily looking at it glass half empty but just trying to understand why this unit would use so much more energy. I can understand the sun impact but the sun is off the side of the house this time of year around 230. A little more background. I had all 3 units installed last June and this unit started icing up on the lines outside last summer and the heads weren’t cooling inside. I called they came out and added a little refrigerant and things improved. The winter came and I saw very high electric bills just using the splits vs boilers/radiators. I turned off the 36k unit and left the 24k unit going. For year over year same month comparison when just using the 24k bill was the same. Previous bills with the 36k on was over double from same month previous 3 years. This is what prompted me to invest in the Iotawatt to learn what was going on.
Just thought I would update if anyone comes across the same issue. Yesterday the compressor failed on this unit. The unit was using over 3300 watts at times when the submittal says max is 2600. I’m really glad I had this device as it proved very useful when trying to convince the installer it isn’t just the sunny side of the house. The thing sounded horrible since this past winter and the reason I got this device in the first place as my bills were very high. Now I’m fighting with installer as they should be replacing the unit and not just the compressor, they started working on this less than 30 days after install when I called about ice on the lines. I would look at other brands other than Mitsubishi.
I’d probably try a different installer first.
Just talked to the installer and they are going to do the right thing and replace the unit vs. replacing the compressor. We’ll see how it goes.
New system installed and what an improvement. The one screen is from 3 days ago and you can see how much energy was being used before the compressor failed. After the new unit was installed it is where I expect it to be compared to the 24k unit.