While reporting hourly heating and cooling demand from my EnergyPlus 9.4 model, I used the Plant Supply Side Heating Demand Rate [W] variable. When I looked at the results, heating demand in the summer appeared lower than expected. So, I reported the Heating Coil Heating Rate variable for all heating coils in the facility.
When comparing the two profiles, I found that the Heating Load is higher when summing up individual coil loads, that the plant level output. Has anyone else encountered this before? What is the most reliable way of estimating simultaneous load?
Below are some charts comparing the two hourly profiles; the blue line denotes the output of Plant Supply Side Heating Demand Rate, while the orange line reflects the hourly sum of individual coil heating rates. The chart units along the y-axis are kBTU/h. Please disregard the "year" values.
Chart 1: Annual profile 
Chart 2: Summer - June to August 
Chart 3: February
Chart 4: June
