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diff --git a/Docs/source/running_cpp/parameters.rst b/Docs/source/running_cpp/parameters.rst
index 7db069a6d..536688609 100644
--- a/Docs/source/running_cpp/parameters.rst
+++ b/Docs/source/running_cpp/parameters.rst
@@ -1091,6 +1091,78 @@ Diagnostics and output
     slice diagnostic if there are within the user-defined width from
     the slice region defined by ``slice.dom_lo`` and ``slice.dom_hi``.
 
+* ``warpx.reduced_diags_names`` (`strings`, separated by spaces)
+    The names given by the user of simple reduced diagnostics.
+    Also the names of the output `.txt` files.
+    This reduced diagnostics aims to produce simple outputs
+    of the time history of some physical quantities.
+    If ``warpx.reduced_diags_names`` is not provided in the input file,
+    no reduced diagnostics will be done.
+    This is then used in the rest of the input deck;
+    in this documentation we use `<reduced_diags_name>` as a placeholder.
+
+* ``<reduced_diags_name>.type`` (`string`)
+    The type of reduced diagnostics associated with this `<reduced_diags_name>`.
+    For example, ``ParticleEnergy`` and ``FieldEnergy``.
+    All available types will be descriped below in detail.
+    For all reduced diagnostics,
+    the first and the second columns in the output file are
+    the time step and the corresponding physical time in seconds, respectively.
+
+    * ``ParticleEnergy``
+        This type computes both the total and the mean
+        relativistic particle kinetic energy among all species.
+
+        .. math::
+
+            E_p = \sum_{i=1}^N ( \sqrt{ p_i^2 c^2 + m_0^2 c^4 } - m_0 c^2 ) w_i
+
+        where :math:`p` is the relativistic momentum,
+        :math:`c` is the speed of light,
+        :math:`m_0` is the rest mass,
+        :math:`N` is the number of particles,
+        :math:`w` is the individual particle weight.
+
+        The output columns are
+        total :math:`E_p` of all species,
+        :math:`E_p` of each species,
+        total mean energy :math:`E_p / \sum w_i`,
+        mean enregy of each species.
+
+    * ``FieldEnergy``
+        This type computes the electric and magnetic field energy.
+
+        .. math::
+
+            E_f = \sum [ \varepsilon_0 E^2 / 2 + B^2 / ( 2 \mu_0 ) ] \Delta V
+
+        where
+        :math:`E` is the electric field,
+        :math:`B` is the magnetic field,
+        :math:`\varepsilon_0` is the vacuum permittivity,
+        :math:`\mu_0` is the vacuum permeability,
+        :math:`\Delta V` is the cell volume (or area for 2D),
+        the sum is over all cells.
+
+        The output columns are
+        total field energy :math:`E_f`,
+        :math:`E` field energy,
+        :math:`B` field energy, at mesh refinement levels from 0 to :math:`n`.
+
+* ``<reduced_diags_name>.frequency`` (`int`)
+    The output frequency (every # time steps).
+
+* ``<reduced_diags_name>.path`` (`string`) optional (default `./diags/reducedfiles/`)
+    The path that the output file will be stored.
+
+* ``<reduced_diags_name>.extension`` (`string`) optional (default `txt`)
+    The extension of the output file.
+
+* ``<reduced_diags_name>.separator`` (`string`) optional (default `,`)
+    The separator between row values in the output file.
+    The default separator is comma, i.e. the output file is in
+    the CSV (comma separated value) format.
+
 Lookup tables for QED modules (implementation in progress)
 ----------------------------------------------------------
 Lookup tables store pre-computed values for functions used by the QED modules.