In the previous problem, it was assumed that the COP will be the same when the outside temperature drops. Given the temperatures and the actual COP at the −10°C winter day, give an estimate for a more realistic COP for the outside −15°C case.

Data from previous problem

On a cold (−10◦C) winter day, a heat pump provides 20 kW to heat a house maintained at 20◦C, and it has a COP_HP of 4. How much power does the heat pump require? The next day, a storm brings the outside temperature to −15◦C, assuming the same COP and the same house heat transfer coefficient for the heat loss to the outside air. How much power does the heat pump require then?