Keep it simple as this the cheapest and the most accurate – Don’t let the salesmen In unless you want automatic reporting.
PUE is the total actual power used to run the computer equipment on the computer floor on it’s own compared to the total power to run all the services and the equipment on the floor. This does not include general office areas and power/Air conditioning usage.
PUE = (Total power into UPS + all peek air conditioning power & mechanical services + all computer room lighting & general power + all power to supply side of all the communications equipment + any computer equipment not on UPS) – (the actual measured power into the computer racks + power into the on floor communications equipment if not already included) Just get your electrician to measure the current (amps) on all these points. It’s as east as this. If you want the differences over the seasons recalculate on hottest day, coldest day and average for spring & autumn and calculate the average, or measure monthly etc.