How could you do this?

Am I right that you'd just need a shed of a reasonable size with an A2A heat pump installed. Would need to work out the heating needs of the shed, and probably insulate a wee bit to make it sensible.

Would you need to heat using an electric heater to confirm the heating needs empirically?

Internal target temp set to 20 degrees for between say 8am and 10pm. Monitor to track electric usage.

Wouldn't even need a whole year of data to be useful. Would even be good just to have a bit of data to see how humid/wet days affect it, and what happens in the external temperature zone of between zero and 7, where funny things MAY happen.

Why reinvent the wheel? A2A heatpumps are in common use in many places, including "difficult" climates like Canada's. There is already a lot of performance data for these. We have climatic regions in Canada similar to the UK (British Columbia, for example).

http://www.nrcan.gc.ca/energy/publications/efficiency/heating-heat-pump/6831

http://www.nrcan.gc.ca/sites/oee.nrcan.gc.ca/files/pdf/publications/infosource/pub/home/heating-heat-pump/booklet.pdf

https://www.cmhc-schl.gc.ca/en/inpr/su/sufepr/sufepr_001.cfm

http://www.ductless.ca/ac/lg.html

https://www.buildinggreen.com/blog/7-tips-get-more-mini-split-heat-pumps-colder-climates

Paul in Montreal.

How could you do this?

COP = Power out/Power in

Power in is the electrical power. Not hard to measure.
Power out is the thermal power in the hot air... for that you need to know the air flow rate and the temperature increase.

I think that's is probably all you need. Don't see why you need insulated sheds etc.

Posted By: ringiYou need to know the heat lost from the hot air, this is very hard unless you have a very well insulated and sealed box.

It's not hard to do. Just measure the temperature of the air as close to the outlet as possible. If you know the supply and return temperatures, as well as the air flow, then you can get the output power pretty accurately. Measuring the flow rate might be a challenge, though.

Paul in Montreal.

μt = (t2 - t1) / (t3 - t1)

where

μt = temperature transfer efficiency

t1 = temperature in outside make-up air before the heat exchanger (oC)

t2 = temperature in outside make-up air after the heat exchanger (oC)

t3 = temperature in outlet air before the heat exchanger (oC)

Posted By: ringiYou are assuming the air comes out at a constant temperature, it may be a different temperature at different places in the output.

True - I measured mine at the closest duct to the heatpump, calibrated with the 10kW auxiliary heater so I could calculate the effective flow rate and then use that to determine the heat pump output. I'm sure it's accurate to about +/- 5%.

Paul in Montreal.

You got a duct that makes it easier, the A2A units in the UK have a long slot the air comes out of directly into the room.