It was a fair challenge, particularly in light of research suggesting that a hybrid - or “heat pump add-on” - can reduce heating bills compared with both a gas boiler-only system and a heat pump-only system.

So, here goes.

During the recent Labour Party Conference, I heard several speakers argue that solar PV and battery storage are sound investments that can cut household energy bills. A DESNZ official made much the same point a few months earlier. That may well be true, although I would still like to see the evidence. What caught my attention was the leap they made next.

The argument was that households adopting solar PV and batteries would then be more likely to install a heat pump. I am far less convinced by that claim. Beyond the obvious financial hurdle - these are two substantial investments - I struggle to see the connection, other than that both are labelled low-carbon technologies.

For the majority of homes connected to the gas grid, installing solar panels and a battery will not automatically make a heat pump the next logical purchase. If the existing gas boiler works and the solar investment is already saving money, why would it?

A hybrid system offers a more credible pathway. Adding a heat pump alongside an existing boiler allows a household to become familiar with the technology and build confidence that it can heat their home effectively. In time, that experience may give the consumer the confidence to dispense with the boiler altogether. Crucially, the proposition is directly about heat and hot water; solar PV and batteries are not.

That is why I see a stronger logic in supporting hybrids as a practical way to accelerate low-carbon heating. This question will become more pressing if the Warm Homes Fund supports solar PV and batteries - which it should, where they demonstrably save consumers money. Public funding is finite. If households are helped to invest in one low-carbon technology but are no more likely to adopt low-carbon heating as a result, less funding will remain to support heat pump installations. DESNZ should therefore distinguish between technologies that cut electricity bills and those that provide a realistic transition route for home heating. Policy should follow the evidence, not rely on a leap of faith.