v0.15.1 (April 20, 2026)

Bug fixes

Fix a bug in :py:func:`pvlib.scaling.latlon_to_xy` where latitude scaling was incorrectly applied to both latitude and longitude components. (:issue:`2614`, :pull:`2712`)
Fix a division-by-zero condition in :py:func:`pvlib.transformer.simple_efficiency` when load_loss = 0. (:issue:`2645`, :pull:`2646`)
Update URLs in :py:mod:`pvlib.iotools.psm4` to use nlr.gov instead of nrel.gov. (:issue:`2701`, :pull:`2705`)
Fix a bug in :py:func:`pvlib.iotools.get_era5` where conversion of precipitation in meters to cm was underestimated by a factor of 10,000 when map_variables=True. (:issue:`2724`, :pull:`2725`)

Use k and cap_adjustment from :py:attr:`pvlib.pvsystem.Array.module_parameters` in :py:func:`pvlib.pvsystem.PVSystem.pvwatts_dc` (:issue:`2714`, :pull:`2715`)
Include ross and faiman_rad in the allowed models within :py:meth:`pvlib.pvsystem.PVSystem.get_cell_temperature` (:issue:`2625`, :pull:`2631`)
Accelerate the internals of :py:func:`~pvlib.solarposition.ephemeris`. (:pull:`2626`)
Accelerate the internals of :py:func:`~pvlib.pvsystem.singlediode` when method='lambertw'. (:pull:`2732`, :pull:`2723`)
Accept negative axis_tilt values in :py:func:`~pvlib.tracking.singleaxis`. (:pull:`2702`, :issue:`1976`)

Add examples for :py:meth:`pvlib.modelchain.ModelChain.run_model_from_poa` and :py:meth:`~pvlib.modelchain.ModelChain.run_model_from_effective_irradiance` (:issue:`1043`, :pull:`2621`)
Add the following terms to the :ref:`nomenclature` page (:issue:`2564`, :pull:`2663`):
Add an overview of IAM modeling functionality in new documentation page :ref:`iam`. (:pull:`2683`)
Add AI checkbox to PR template, and auto-generate a comment on PRs from first-time contributors regarding AI and contributing guidelines. (:issue:`2617`, :pull:`2624`)
Clarify :py:class:`pvlib.pvsystem.PVSystem` parameter module_type is optional. (:issue:`2634`, :pull:`2713`)
Fix a broken docstring reference to grounddiffuse in :py:func:`pvlib.irradiance.poa_components` (:issue:`2089`, :pull:`2708`)
Add :ref:`core-guidelines` to the :ref:`introduction-to-contributing` page. (:issue:`2716`, :pull:`2726`)

Add test to verify that :py:func:`~pvlib.transformer.simple_efficiency` produces consistent results for vectorized and scalar inputs. (:issue:`2649`, :pull:`2661`)

Update all NREL references to NLR (National Laboratory of the Rockies) following the laboratory rename and domain migration from nrel.gov to nlr.gov. Rename NREL_API_KEY environment variable to NLR_API_KEY. (:issue:`2701`, :pull:`2705`)