The evidence is that reducing load speed is definitely worth the effort (see the business case for speed).
The TLS session is a pain and it is unfortunate that the browser vendors are insisting on it, as there is nothing in HTTP2 that prevents plain text. For a low load system, were CPU costs are not the limiting factor, TLS essentially costs you one RTT (round trip time on network).
HTTP/2 and specially HTTP/2 push can save you many RTTs and thus can be a big win even with the TLS cost. But the best way to determine this is to try it for your page. Make sure you use a HTTP/2 server that supports push (eg Jetty) otherwise you don't get all the benefits. Here is a good demo of push with SPDY (which is that same mechanism as in HTTP/2):