Short answer is no as a power meter requires 3 wires whereas a plug in MCB is only 2 wire

That's a good answer, damn it.

Having said that, if you can measure current with no wires with a clamp meter and voltage with two wires with a volt meter... why can't a power meter be two wired?

Do more thinking, breaker is single pole switching the phase and no ability to even measure supply voltage.

Perhaps have a look at Shelly ProEM. What sort of automation capability do you want? To control the heat pump?

Duh! Of course! You would have to guess the voltage and have a rough estimate on power. 

Bear in mind that without a neutral, there is also very limited power available for the meter to use itself.

You will need a neutral if its going to have any computing capability. Most with a screen take 2x DIN positions and TBH its better and more readable at that size. If you want some metering that doesn't need to display on the unit itself and some home automation why not something like this? You don't need to pass the neutral through it - just the load but need at least a small neutral at the top for it to get its power off.

https://www.aliexpress.com/item/1005006381237359.html

Any sparky who is willing to install that should be prosecuted.

Any homeowner who installs that also should be prosecuted. 

OP appears to want something that can be installed into a legacy fuse-carrier base without a sparky. 

SomeoneSomewhere:

 

Any sparky who is willing to install that should be prosecuted.

 

Any homeowner who installs that also should be prosecuted. 

 

 

 

OP appears to want something that can be installed into a legacy fuse-carrier base without a sparky. 

 

I agree here, only trust trusted MCB brands, as these are designed to protect your wiring in the event of overload. You might not get insurance if you installed a non NZ/AU classified product.

I personally use Shelly devices to measure the current/voltage along side a standard MCB.

It's not just that. Those styles of current meter pass the whole load current through the meter, so you are relying on good terminals and terminations. Disconnect functions like relays are worse.

It's also got electronics across the line, so you have flashover and fire risks from that. 

And it's in a plastic enclosure so there's also flammability concerns.

Basically anything that touches mains is quite high risk .

The only thing it doesn't have to meet is primary-secondary isolation.

SomeoneSomewhere:

 

OP appears to want something that can be installed into a legacy fuse-carrier base without a sparky. 

 

Yep. At some point we'll get the old main switchboard replaced at which time we'll have better options.

There are clamp on CT based ones all over the place for very cheap that are somewhat accurate.

If you want to risk an antique panel to put the clamp on is another matter tho, as there is a good chance its full of spiders, asbestos, and crumbling rubber insulation. They still need to have a L and N to them for the voltage and phase reference and they are not in a ready to use form, you need an enclosure and a cable and plug etc. There are more pricy solutuions that have the guts in a ready to plug in box, but they were getting up to 10x the price of the cheap 1 or 2 CT tuya based things.

Also, not all of them deal with bidirectional power, as I found out with the one on the garage that would show it consuming when the solar was actually generating. The more expensive refoss one I got handles it fine, and I was able to put it in a small din box beside the panel and run the CT wires in easily enough.