If you just want to kick the tires, I’d recommend opening a free account with influxdata. You would need to setup an NGINX proxy to support HTTPS, but that’s easy, especially if you already have a RPi running on your LAN. It’s incredibly fast, and has an integrated dashboard system to produce flex queries and plot them. Pretty much just what grafana does.
The free offering is full functioned, limited only to three month’s data. The next release of IoTaWatt will support native upload to 2.0.