I love this, and did something similar.

If you haven't thought of it already, some estimations are probably worth considering - electricity and water can be more or less stable, and you might benefit from taking those baseline costs out of your calculation.

Also, it might be useful to add metadata in the form of tags or tag-groups in your spreadsheet; this will give you a bigger/more nuanced dataset if/when you have a hankering to analyze your behavior.

Less usefully, it would be cool if it looked like Civ.