Documentation Question Re: readthedocs about install instructions.

[electronspluscode]

Full Disclosure: Not a very strong coder or energy system modeler so please correct me and apologies if this is a basic operator error on my part. I think this question is more a reflection of my not fully understanding how the different parts of pypsa , pypsa-usa, and solvers fit together then a specific issue with the code. That said, imagine I am not alone in this.

Reviewing the pypsa-usa docs ( https://pypsa-usa.readthedocs.io/en/latest/about-install.html ) to get started and note Step 4 is install a solver. But know from the pypsa documentation ( https://docs.pypsa.org/stable/home/installation/ ) that pypsa "ships with the open-source solver HiGHS by default." Looks like the current pypsa-usa enviornment.yaml and pyproject.toml files include pypsa==0.30.2 and highspy.

Wouldn't this make step 4 of the install redundant because by installing highspy as part of the dependencies, you are thus installing HiGHS? Additionally, if you try to use a more recent version of pypsa the pyproject.toml also includes HiGHS (i.e https://github.com/PyPSA/PyPSA/blob/master/pyproject.toml ).

Recognize pypsa has grown massively in the past 18 months including with the recent 14th Oct 2025 launch of pypsa 1.0 ( https://docs.pypsa.org/latest/release-notes/ ), and pypsa-usa is under active development so the documentation step 4 might have been necessary initially, but I do not believe it is now.

Looks like the read the docs documentation was last updated in Aug or Sept 2023. Wonder if we could please update this to reflect that it is not necessary to install additional solvers so that it is a bit more straightforward for a new user?

Thanks!

[wingerter]

Hi @electronspluscode , I think you're right! For HiGHS there's nothing extra to do in Step 4.

highspy (the Python interface to HiGHS) is already pinned in workflow/envs/environment.yaml:

- highspy

So when you create the env in Step 3 (mamba env create -f workflow/envs/environment.yaml), HiGHS is installed automatically and is ready to use. You just need your solving config to point to highs (the default), I think.

Step 4 only really matters if you want a different solver. Gurobi is also in the environment (gurobipy), but it still needs a separate license to actually run; open-source HiGHS works out of the box.

It might be worth a small docs note that HiGHS needs no separate install and that Step 4 is only for alternative/commercial solvers.

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Happy to open a PR for that if it'd help.