There is no point adding a huge amount of solar to your house to make up for very high energy usage, you will be throwing good money after bad. You need to know where your energy is going, so that you can focus your time and money on improving the parts of your house that are actually costing you money. The best way to do this is with energy monitoring, so you know how much power you are using, and when, and ideally what is using it. Below are the different energy monitors I have tried and recommend.

PowerPal

Powerpal is great, however it is very limited. It will only monitor power you are importing, and it needs to connect to your phone with bluetooth. This means if you already have solar you can't tell how much you are exporting. Connecting via bluetooth means your connection range is quite limited, especially if the meter box isn't right at the front of your house. It only stores limited data on the device meaning if your phone doesn't connect and sync regularly you can loose data. The main upside is its cheap due to not needing a sparky to install it (it just watches the blinking light on your meter), and its even free in Victoria.

IotaWatt

This is what I personally use for the majority of my energy metering. It has to be installed by a sparky however it can be installed outside your switchboard, which is great as there is rarely lots of spare room. It uses usb for power and a transformer to get the mains voltage, so I have a double USB GPO installed next to my switchboard where it lives. It can monitor up to 14 channels, (any multi-phase appliances or feeds takes multiple channels, e.g. 3 phase mains uses 3 channels, and 3 phase solar uses 3 more, so you would have already used 6). As it is at the switchboard you can monitor any entire circuit you have. I have mine monitoring the main input, solar, hot water, oven, induction, lights, RCAC etc. Having 14 channels gives you lots of options to monitor many circuits. The main downside is because of all the channels it is not the cheapest to buy. The interface isn't also the most user-friendly, though it is very powerful. I have mine sending all the data to Home Assistant so I can display it how I want, as well as use it to automate parts of the house.

Shelly

Shelly makes lots of smart home devices, and quite a few of them have energy monitoring. I use some Shelly 1PM's that are hard-wired by a sparky behind some "dedicated" GPO's for things that stay plugged in, like Dishwasher, and Washer and Dryer. Shelly also integrates with Home Assistant, so I can see and use the data all in the 1 place. Shelly also make monitoring devices made to monitor whole circuits with current clamps. Shelly EM is perfect for controlling a resistive hot water system, as it can monitor 2 circuits, e.g. mains, and solar. It also has a contactor output to control a contactor to turn the hot water on/off. With this you could wait for mains to be exporting enough power to turn hot water on, then turn it off when you start importing to much. There are many other models like Shelly 3EM, which can monitor 3 circuits, and mounts in your switchboard like the RCBO's. It can monitor 3 circuits, and also have a contactor output to control a load. You could use multiple Shelly 3EM's to monitor lots of circuits, however I didn't choose that option because they take room in the cramped switchboard and ends up more expensive per circuit monitored, but would be great if you didn't want to monitor so much.

There are many other options you could use, and I'm sure lots of them work great, however these are the ones I have tried and I know works well.