[jeff5may]

In general, all of the manufacturers inflate their EER / SEER / HSPF ratings on banner ads, posters, line art, etc. Most likely, the advertised values are peak values, not hard ASHRAE or ARI test numbers over the range of operation. The easy-to-see numbers are inflated like wattage ratings of knockoff audio amplifiers and speakers! The main number-inflating factor in the geo heat pump testing is that the numbers are calculated without water pumping power in the equation. This is one big reason why the larger-capacity units nearly always beat the smaller units in the standardized tests, and why the numbers are better in heating mode vs cooling mode.

Let's say we are using a super duper waterfurnace 7 series, with a pump-and-dump borehole with 65 degF source water temperature (not totally unrealistic). At the high end of its capacity range, the COP is going to be around 5, and the unit is going to greatly exceed its BTU rating, maybe moving 140% of its rated heating capacity. As we slow down the compressor to reach rated capacity, the COP might soar to above 7 at its rated capacity, maybe even reaching 8 at normal water pump speeds. If we then run the water pumps at full throttle, the instantaneous peak COP will rise even higher (near 10-11), then fall off as the balance point is reached. Believe me, the marketing teams will encourage the engineers to push the envelope as far as they can to inflate performance numbers.

Of course, those with a good grasp at the factors at play inside the box and elsewhere in the system are going to voice skepticism when presented these numbers. For those potential customers, most sales pros have no problem producing spreadsheets common to the HVAC industry which present a more realistic picture of actual field performance. But there is a major tendency in the entire residential realm for the manufacturers to quote inflated values on big ads. Some of the less reputable companies don't provide enough test data to establish a level comparison, making it incredibly difficult or impossible to do so objectively.

My main point here is there are so many configurations and factors to consider, that you really have to ask the right questions and look at a number of measurements to get an apples-to-apples comparison between units. Many GSHP units don't even have water pumps or fans inside the box, so presenting the total system performance questions has to be narrowed down from the getgo. The governing bodies have decided not to do this narrowing down, giving the manufacturers extra leeway during the certification process.