Cool formula for calculating your mini split COP.

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Minister of Fire
Sep 20, 2013
Branford, CT
Saw this on another forum where you can calculate the COP of your min split with just 3 pieces of data. I know many have energy monitors so you need to have current electrical consumption.

CFM- This is on your mini split submittal sheet. They all have the CFM's listed low to High. You can also use a 30$ dwyer manometer for more precision.

Delta T- Simple thermometer measuring the difference between return supply.

Electrical consumption- Many options to choose from. Clamp on ammeter is probably cheapest and easiest.

I have temperature sensors on my return and supply and an energy monitor on each mini split circuit. So my data is all stored.

Here is how its done

CFM × Delta T × 1.08/3.412 then divide by total electrical draw.

Here were some real numbers from one of my splits.

CFM on low 250
Delta T 21 degrees
Electrical consumption 200 watts.


1661÷200 watts= 8.30

So at low speed my split is running at a COP of 8.30 or 830 percent efficiency! Most of the published data for mini splits is done at full speed. These units will run at incredible efficiency at low speeds. My numbers match up perfectly with the data published at the NEEP cold climate list. They have some COP numbers at low speed listed.

Screenshot_20200111-110315_Monitor.jpg Screenshot_20200111-090151_My AcuRite.jpg