Heating and Cooling Component Loads in Ekotrope

If you find yourself diving into the "Advanced Details" section of Ekotrope's Analysis page and comparing results to other software tools like REM/Rate, you will want to understand the differences in calculation methodology.

The Ekotrope energy simulation engine runs on an hourly, single zone model.  Ekotrope sums hourly loads to determine an annual total, but only tallies component loads that actually force the HVAC system to work.  For example, on a cool summer night (or day), a home will have some internal gains that serve to increase the temperature of the home, but it will also have some ventilation, forced and unforced, that will act as a heat release.  If the heating and cooling loads for a given hour are balanced enough such that the temperature of the home is not forced outside the thermostat setpoints, the component loads are not added to the annual total.  This means that a home could go through long periods, especially in shoulder seasons, where all the loads of a home are in balance and none are counted toward the annual component loads tally.

REM/Rate, in contrast, tallies all loads regardless of whether they force the HVAC system to work, but counts certain loads as negative if they have a net-reducing impact.

For example, it is very common to see internal gains loads in REM/Rate that are significantly (even 10x) higher than Ekotrope, because net-reducing loads like whole-house ventilation and infiltration are tallied as well and serve to balance the total load of the home.  Ekotrope just runs this balance on an hourly basis and only tallies loads that matter for fuel consumption.