How can I speed up web part loading times?

I have a SharePoint site with a performance point dashboard which contains a number of webparts. The initial page load time is around 1s according to F12 Dev tools. After this I see spinning green wheels while the webpart content renders. This takes around 5 seconds for each web part and in dev tools I can see a number of calls to /_layouts/15/ReportServer/RSViewerPage.aspx These calls correspond to the number of webparts on the page and run in parallel.

Is there any way to speed up the rendering time of the pages? There is minimal time spent in SQL returning the results so this seems purely a rendering issue. Can we cache the html output or cache the dashboards somehow so that we can have a 1s wait rather than 6-10?

I don't need the dashboards to refresh often so a static view of them should be fine.