I think it should be possible. If you are thinking of battery storage at any time, I have looked at these from Sigenergy, which allow charging from a generator or compatible EV 

https://www.sigenergy.com/en/products/gateway

@bontwoody Thanks, that a very interesting avenue I had not thoght of!

@pipcart, good topic!

I do/did. I have a 4KW Hyundai petrol genny which can be plugged into an external socket and feeds the manual change over switch to energise the house circuit.  It covers most of the demand for the ASHP once it is running and the temperature is up but we have to ensure that all other use is severely curtailed, especially the freezers/fridge. The combined load of high heat demand and them craps out the genny. I now usually just leave the heat pump off for power cuts. If it turns into a days long outage, haven't had one of those for a while, then the plumbing was left with manual change over valves to isolate the heat pump and run the old LPG boiler to provide heating, which can be adequately powered by the genny.

Posted by: @pipcart

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@bontwoody Thanks, that a very interesting avenue I had not thoght of!

Having a heatpump on its own distribution board is great, if you have spare space. It may become easier to add to it. 

There are plenty of other options of inverter+battery coupling that would do this. 

You have two type of systems:

1- a battery that includes an inverter (the component that is connected to the electrical supply of the house). This may help if you just want a small 5kw to keep the heat pump from freezing

2- an inverter that charges and discharges one or several batteries. Typically with three 16kw batteries you can run a heatpump for a day. Some of these would sell for £4 or 5k + labour and certification

You may also benefit from option 2 having sufficient storage to run the heatpump on a cheap ASHP tariff. If your heatpump is working more efficiently during the day, your electricity 

I have a Solis inverter and started a thread on this that gives you a better idea of what is involved at https://renewableheatinghub.co.uk/forums/energy-storage/solis-s6-eh1p8k-l-plus-why-i-chose-it-and-what-ive-learned-so-far/paged/1/

My system costed about half+labour (I only have one 16kw battery) and is able to keep the whole house power going for a day and a half of power outage. 

Beware of horror stories about lithium batteries. The ones we are discussing here are safe. This may help https://renewableheatinghub.co.uk/forums/energy-storage/lifepo4-lithium-battery-fires-and-explosions/paged/3/#post-54522

@abernyte Many thanks for taking the time to reply. It's good to know that it is possible.

@batpred Thanks again. Lots to consider 🙂

@abernyte 

Thank you for sharing. 

Just wanted to make sure you are aware that feeding power into an RCD protected circuit may burn the solenoid in the RCD/RCBO. This could mean the circuit is no longer protected as expected. 

There´s a thread here that goes into more detail on a typical solution https://renewableheatinghub.co.uk/forums/energy-storage/buying-large-amp-bidirectional-rcd-and-rcbo/#post-51433

Thanks...the sparky handled all the technical bits and bobs and out here he does lots of off grid and change over stuff. I trust him.  I also have a complete wired 13amp generator only board and circuit in the house, which doesn't touch the change over switch or any of the grid fed circuits, with genny only sockets along side the key appliances. It has an external socket to plug the genny into, near where the genny runs outside and of late we have just been using that. 

It would be fine if I could get a smart meter signal then I might invest in a battery to make all of this redundant!

@batpred Thanks for the warning. definately a job for a qualified professional!

Posted by: @pipcart

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@batpred Thanks for the warning. definately a job for a qualified professional!

Definitely and professionals sometimes miss it.

I had a similar situation when my EV charger was fit. It is not bi-directional ready, but I remember it being discussed...