There is one question that anyone, especially a Social Landlord, should answer first when they begin to determine a retrofit strategy. But at the moment, nobody is asking it.

The question is “how much do you want your residents’ energy bills to drop by?”.

It’s not being asked because, for many years, we’ve approached retrofit as an exercise in energy demand reduction from a primarily technical standpoint (and twenty years ago, I’d have been arguing that too!). This has been fuelled by the transfer of terms like “fabric first” from the new build world, where it’s broadly sensible, to the retrofit world, where its’ broadly not.

It’s also been built from the understanding that energy reduction means carbon reduction, which for many decades was generally true. This mindset is still embedded in much of our regulation and even some leading practice, where we’re still measuring in energy not the carbon it produces.

To prevent the most severe impacts of climate change, our future must be zero carbon—but it doesn’t have to be zero energy. In fact, one could argue it doesn’t even need to be ‘low energy,’ provided we are prepared to invest in significant infrastructure upgrades for large-scale generation and storage of zero-carbon energy. The practical approach lies in striking a balance: reducing energy consumption to a reasonable degree to help offset the costs of scaling up such infrastructure.

In this context, retrofitting our homes to become zero carbon is simple – electrify them. Electricity is the only widely used energy ‘source’ that can achieve zero carbon emissions. With the progress to date, and government plans, it seems likely that it will be zero carbon for some periods of most days in the 2030s. Homes that aren’t “smart” enough to just use the zero carbon electricity by shifting their demands will be low carbon and probably remain there for some years to come. Those that can move their demand (by storage in or near the home), will be able to be zero carbon during the 2030s.

Electricity can generate enough heat, hot water, and plug-in power to make any home of any size comfortable, or for that matter, any building. That’s true for electric powered heat pumps, but also for direct electric alternative heating sources. It’s really only a question of sizing the heating source, and ensuring the distribution and emission of that heat into the homes is also designed to suit whatever system is preferred. The only question is how much electricity will be needed to achieve it?

Combining all of the above means every home will electrify and become zero carbon. Whether it becomes zero carbon in the 2030s or 2060s will likely depend on how “smart” the home is within this timeframe. The challenge of decarbonising homes will therefore naturally complete once all homes have fully electrified. From this perspective, if their energy bills are no higher than they were when they were burning fossil fuels, this could be argued as being acceptably “out of scope” of the climate emergency: Bill parity with past costs could be seen as the point when retrofit stops being about the climate emergency.

For Social Landlords and many beyond, the issue of fuel poverty is heartbreakingly real, and a national outrage. Hence “bill parity” might tackle climate change, but it misses an opportunity to tackle fuel poverty.

This is why the first question for any retrofit strategy is “how much do you want your residents’ energy bills to drop by?”. Achieving net zero is a given (eventually), but tackling fuel poverty isn’t. Setting a number on this question sets your pathway for homes, for example, a 10% energy bill reduction will likely use broadly cost effective retrofit measures, and leave room to leverage private investment. Conversely, a 50% energy bill reduction for your residents is commendable (for fuel poverty), but will drive expensive deep fabric improvements and leave no room for recycling investment with shared benefits to fund future works.

If you’re setting your retrofit strategy, first get your whole organisation to agree if, and by how much, you’re reducing your residents’ energy bills. Everything afterwards is just maths and physics…