Skip to content

Document the index convention of read_epw #2894

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
cdeil wants to merge 3 commits into
base: main
Choose a base branch
from
Open

Document the index convention of read_epw #2894

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
d945142
Document the index convention of read_epw
cdeil Oct 9, 2026
b9a0774
Add the pull request number to the what's new entry
cdeil Oct 9, 2026
48c54dc
Apply EPW reviewer wording and merge current main
cdeil Nov 6, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 6 additions & 0 deletions docs/sphinx/source/whatsnew/v0.16.2.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,11 @@ Documentation
and :py:func:`~pvlib.irradiance.get_sky_diffuse` docstrings.
(:issue:`2897`, :pull:`2904`)

* Document in :py:func:`pvlib.iotools.read_epw` that each record is labeled
with the start of its hour, unlike :py:func:`pvlib.iotools.read_tmy3`, and
how to label it with the time given in the EPW file. (:issue:`1156`,
:pull:`2894`)


Testing
~~~~~~~
Expand Down Expand Up @@ -80,3 +85,4 @@ Contributors
* :ghuser:`bfs2021`
* :ghuser:`xiajiahang`
* Jakub Krasuski (:ghuser:`Blizzeq`)
* Christoph Deil (:ghuser:`cdeil`)
13 changes: 13 additions & 0 deletions pvlib/iotools/epw.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,19 @@ def read_epw(filename, coerce_year=None):
+-------------------------------+-----------------------------------------+


.. warning:: In hourly EPW files, radiation totals and illuminance
averages cover the hour *ending* at the file time; temperature,
humidity and pressure are values *at* that time [1]_.
``read_epw`` labels all fields with the *start* of the hour (EPW
hour 1 becomes 00:00), while :py:func:`~pvlib.iotools.read_tmy3`
uses the *end*.

To use end-of-hour labels, add one hour to the index:
``data.index = data.index + pd.Timedelta('1h')``. The record for
31 December's final hour then has the label 1 January 00:00 of
the following year. No records are added or removed.


References
----------

Expand Down