alifeee's notes - comparing EPC certificates with git-diff

comparing EPC certificates with git-diff # source

tags: git-diff, scripting, housing • 484 'words', 145 secs @ 200wpm

Our house just got a new EPC certificate. You can (maybe) check yours on https://www.gov.uk/find-energy-certificate.

I'm interested in easy ways to see change. Trying to compare the old and new webpages by eye is hard, which leads me to text-diffing. I can copy the contents of the website to a file and compare them that way. Let's. I did a similar thing a while ago with computer benchmarks.

I manually create two files by copying the interesting bits of the webpage, called 1 and 2 (because who has time for .txt extensions). Then, I can run:

git diff --no-index -U1000 ~/1 ~/2 > diff.txt
cat diff.txt | sed -E 's#^\+(.*)#<ins>\1</ins>#' | sed -E 's#^-(.*)#<del>\1</del>#' | sed 's/^ //'

The latter command turns each into HTML by turning + lines into <ins> ("insert"), - into <del> ("delete"), and removing leading spaces on other lines. Then, I can whack the output into a simple HTML template:

<!DOCTYPE html>
<html>
  <head>
    <style>
    body { background: black; color: white; }
    pre { padding: 1rem; }
    del { text-decoration: none; color: red; }
    ins { text-decoration: none; color: green; }
    </style>
  </head>
  <body>
<pre>
diff goes here...
<del>del lines will be red</del>
<ins>ins lines will be green</ins>
</pre>
  </body>
</html>

The final output is something like this (personal information removed. don't doxx me.)

Energy rating D

Valid until ~~05 February 2025~~ 05 February 2035

Property type Mid-terrace house Total floor area ~~130 square metres~~ 123 square metres

~~This property’s energy rating is D. It has the potential to be C.~~ This property’s energy rating is D. It has the potential to be B.

Features in this property

Window Fully double glazed Good Roof Pitched, no insulation (assumed) Very poor ~~Roof Roof room(s), no insulation (assumed) Very poor~~ Roof Roof room(s), insulated (assumed) Good ~~Lighting Low energy lighting in 64% of fixed outlets Good~~ Lighting Low energy lighting in all fixed outlets Very good Secondary heating None N/A

Primary energy use

~~The primary energy use for this property per year is 303 kilowatt hours per square metre (kWh/m2).~~ The primary energy use for this property per year is 252 kilowatt hours per square metre (kWh/m2).

Good job on us for having 100% low energy lighting fixtures, I guess...

Really, this is a complicated way to simplify something. I like simple things, so I like this.