I discovered that, in fact, the OpenStudio workflow gem does by default request timestep output variables. See here.

If you are using an OSW to run your simulations, it looks like you can avoid the timestep outputs by using the skip_energyplus_preprocess option like so. We've been using this option for so long in our residential simulations that I forgot what the default behavior is...

This is part of the URBANopt output. From my first look there isn't any simple way to remove those outputs. However, since the simulation is going at whatever timestep you've selected, I don't think removing select columns will significantly impact the simulation time.

If you have, as you say, huge UO models, the number of buildings is driving the simulation time to a much larger degree.

I'll continue investigating with developers.

It sounds very strange...

I could easily reproduce this in OpenStudio by starting a new file (I have used version OS App 1.7.0 and SDK 3.7.0), drawing a simple box model (one thermal zone), applying the default ASHRAE office space type, construction set, and schedule set (including heating and cooling setpoints), activating ideal loads in the thermal zones tab, and without applying any measure (not even the default reporting measure), launch a whole-year simulation with a 6-timestep configuration.

The following code lines always appear at the end of the IDF file generated in run folder, corresponding to Output:Meter objects not configured by the user (and not present in the original OSM file):

Output:Meter:MeterFileOnly,
  NaturalGas:Facility,                    !- Key Name
  Daily;                                  !- Reporting Frequency
Output:Meter:MeterFileOnly,
  Electricity:Facility,                   !- Key Name
  Timestep;                               !- Reporting Frequency
Output:Meter:MeterFileOnly,
  Electricity:Facility,                   !- Key Name
  Daily;                                  !- Reporting Frequency
Output:Meter,
  Electricity:Facility,                   !- Key Name
  Timestep;                               !- Reporting Frequency
Output:Meter,
  NaturalGas:Facility,                    !- Key Name
  Timestep;                               !- Reporting Frequency
Output:Meter,
  DistrictCooling:Facility,               !- Key Name
  Timestep;                               !- Reporting Frequency
Output:Meter,
  DistrictHeating:Facility,               !- Key Name
  Timestep;                               !- Reporting Frequency

Even more, if I model a DHW system, Air-loop based HVAC system, etc., you can get a lot more Output:Meters, always in timestep reporting frequency.

In this simple box model I get the output in sql and eso files for only the Output:Meter objects corresponding to DistrictCooling:Facility and Electricity:Facility, as DistrictHeating:Facility is not supported in the last versions of EnergyPlus (now it's called DistrictHeatingWater:Facility).

Any idea on how to avoid this?

UPDATE: I could reproduce it identically also with OpenStudio App 1.5.0 (SDK 3.5.1).