My house was built in 1979 it has aluminum double panel and I am planning to switch them out to vinyl windows with grids but they are so expensive. Should I keep the aluminum because the new windows are double panel as well so energy wise is the same just different looks.
If you're just replacing the windows for the sake of going from double pane, clear glass for double pane with low E and Argon, the results will be slight and you are probably better served to keep your existing windows if they are well functioning.
That all being said, most aluminum windows that I see are both non-well functioning as well as terribly leaky.
You will likely save more money from the airtightness improvements comparing a good well sealed well functioning replacement window as compared to your existing aluminum windows.
If however your aluminum windows work well and seal tightly the math is not in your favor when it comes to changing out those units for newer units with low E and Argon.
Of course, there are also huge condensation issues in most cases when it comes to aluminum windows which might be problematic in your case.