Legalise AC

Clean energy abundance should mean sweating less indoors

On a hot sunny day in 2035, Britain will face an unusual challenge: solar farms alone will produce more electricity in a single hour than the entire grid currently generates in 90 minutes. Factoring in wind and nuclear, Britain will be generating 15 GW more than today’s peak power demand. In 2035, for a little while, Britain will have abundant clean energy.

If grids don’t balance, bad things happen. Britain’s National Energy Systems Operator (NESO) is counting on a surge in demand from green hydrogen, data centres, and electric vehicles. They may be right, but Britain will still be relying on France (or Denmark or Holland) not to have a similar surplus of power so they can buy ours via interconnectors. Even then, we will need some solar farms to switch off despite the fact that solar power is essentially free to produce at the margin.

Spain is effectively a decade ahead of Britain on solar. Even though they’ve only got 30GW or so installed—about half of Britain’s target—a combination of sunny skies, tilting panels, and a smaller population means Spaniards are getting roughly the same amount of solar power per capita that Brits will get in 2035.

Spain is a way-off the green hydrogen and EV uptake levels that NESO are banking on for Britain. But, one thing that is helping mop up that extra demand is AC. Around two-fifths of Spanish households have air-conditioning. If Britain saw the same level of uptake (about 12m households with AC) then it’d halve our 15GW surplus. Instead of paying solar farms to switch off, Brits would pay pennies (or even less) to cool their homes.

AC isn't without issues. Demand peaks in the evening, just after solar generation declines. However, that’s not as big of a problem as it first seems:

• Homes can be 'pre-cooled' during the day when solar power is abundant.

• Battery storage, increasingly affordable, can also smooth out demand.

Opponents of AC usually oppose it out of a reflexive anti-consumption environmentalism. In their eyes, comfort can never come ahead of tackling climate change. To quote one Guardian article: “When it’s 26C outside, the average British home simply doesn’t need air-conditioning. It might feel nicer, but making you a little more comfortable isn’t the government’s job.”

But, there’s two key reasons why ‘green’ opposition to aircon is misguided.

1. Britain’s grid is going green. Britain’s last coal power station closed last year. And from 2030, at least 95% of our electricity will come from green sources. On those hot sunny days when aircon is most useful, Britain will have a surplus of clean power.

2. Aircon could be the secret to getting consumers to make other green switches. The potential for air-to-air heat pumps to cool, as well as heat, our homes could be key to persuading consumers to get off gas and switch to greener flexible electricity tariffs.

For smart tariffs, AC is a gamechanger. Running AC on full-blast isn’t cheap on a standard variable tariff. One hot week can set you back £20. But, if you were to use a smart tariff like Agile (Octopus) then you could take advantage of what they call plunge pricing. That’s where you are literally paid to turn on your washing machine, dishwasher, and, yes, your AC. There were around 110 one-hour periods where electricity was cheaper than free last year. As we put more wind and solar onto the grid, the number of ‘plunge pricing’ periods is set to grow massively. In fact, by 2027 analysts reckon there will be more than 1,000 each year. The public tends to be sceptical of time-of-use pricing. Most consumers are unlikely to swap stable predictable prices for the opportunity to save a tiny bit of cash by changing when they run their washing machine. The opportunity to save £150 each summer on AC, on the other hand, just might be the trigger.

If persuading people to switch to smart tariffs is a hard task, then getting them to rip out their boilers is on a whole other level. Big grants–up to £7,500 under the Boiler Upgrade Scheme–are available to deal with the upfront cost of buying and installing a heat pump. Even with the UK’s high electricity prices, heat pumps are so much more efficient than gas boilers that electrifying your home heating should mean long-term bill reductions. But that’s a lot of disruption for a relatively small saving even after accounting for the generous support on offer.

But, there’s another reason to electrify your heating system. Some heat pumps, specifically the air-to-air variety have another use. They don’t just pump heat from the outside in. They can pump inside heat out. In other words, they’re air conditioners. But there’s a problem, air-to-air heat pumps do not benefit from the Government’s two main pro-heat pump policies. They’re cut out from the Clean Heat Market Mechanism, which forces boiler manufacturers to sell a growing share of heat pumps, and they don’t get the substantial Boiler Upgrade Scheme (BUS) grants.

Why are air-to-air heat pumps excluded? There’s two key reasons. To start, there’s a desire to only subsidise necessary carbon cuts. Grants for air-to-air heat pumps would, in essence, be subsidising ‘optional comfort’ as well. But, more importantly, air-to-air heat pumps are compatible with keeping a gas boiler for hot water. Running a hybrid system (electric for heating and gas for heating) will still be lower carbon than gas-for-everything, but it won’t deliver the same emissions reductions.

If you look around the world at countries with high rates of heat pump adoption, Britain’s approach is an outlier.

• Norway has the highest heat pump adoption rate in the world. Almost all of them (85%) are of the air-to-air variety.

• Japan, where humid summers make aircon essential, has an even higher heat pump uptake. In practice not all households use their air-to-air pumps for heating owing to high electricity costs. Policy is now focused on persuading (and incentivising) households to also buy a separate stand-alone heat pump water heater.

• 7.5m French households use an air-to-air heat pump. Demand for cooling from air-to-air heat pumps paired with tech-neutral subsidy schemes are driving consumers to electrify home heating.

At the moment, just 5% of households have AC. That’s extremely low by international standards. In Germany, the rate is almost four times higher and in France, five times as many households have AC. Britain’s AC units are typically inefficient mobile units that, crucially, can’t be used for efficient home heating.

Britain may lack Norway’s cheap hydro power and Japan’s humid summers, but rising temperatures are leading more Brits to look into getting AC. The Government predicts that by the end of the century AC usage will be the norm in large parts of Britain. In the South, where most people live, they reckon four-fifths of households will have AC by 2091. Admittedly, that’s a long way off but there’s a clear direction of travel. Why not piggy-back off that trend to get consumers to switch to a technology that most experts believe is essential if we are to get anywhere near hitting Net Zero by 2050?

There’s some progress on this front. One major barrier to getting consumers to install reversible heat-pumps has been removed and the Government is consulting on removing another is under threat.

Until recently, households looking to install a heat pump to heat and cool their home were required to apply for planning permissions. By contrast, heat pumps solely used for heating were considered permitted development in most cases. A recent expansion of PD rights for heat pumps, which allows them to be installed in more locations without getting planning permission, also expanded the right to heat pumps that “may provide cooling as well as heating”.

That’s one big hurdle removed, but cost is another. There may be progress on this front. DESNZ recently closed a consultation on extending the Boiler Upgrade Scheme (BUS) to air-to-air reversible heat pumps. Options included allowing buyers to access grants if they paired them with a heat pump water-heater or offered 50% BUS grants for reversible A2A units paired with gas boilers. Britain’s current approach to ‘clean heat’ has assumed that Whitehall is able to pick the best technology. They may be right this time, but the government's track record of picking technologies is far from spotless. Making these changes would, like other countries, put consumers back in control.

Yet, some barriers still remain.

How building regulations are holding back reversible heat pumps

‘Part O’ Building Regulations cover overheating.

Among other things, they are the cause of the proliferation of extremely ugly tiny windows in new builds around Britain. Big windows let more sunlight in. In general, this is a good thing and a reason why basement flats are typically cheaper than second floor flats. In fact, planning permission is often refused because of its impact on another households' right to light. Yet, there’s one drawback from more sunlight. Your house gets hotter and on the hottest days of the year, unpleasantly so.

Part O attempts to deal with this by restricting total glazing levels. If you live in a ‘high-risk’ area such as London, and lack cross-ventilation then at most 11% of your most glazed facade can be glazed – and just 30% of the floor area of the most glazed room can be glazed. Northerners get a bit less light from the sun, so to compensate they get a fifth more glazing.

It’s hard to grasp what this means in practice. So let’s use some pictures. In the picture below, around a third to two-fifths are glazed.

To comply with Part O regulation, at least every other window would need to be blocked up.

There’s a caveat. This is what’s known as the simplified method. In theory, developers can pay experts, who apply something known as the comfort criteria, to include bigger windows. Expensive dynamic modelling can be used to account for the use of shutters and awnings, window orientation, and the practice of opening windows.

After all, windows don’t just warm places up. They also allow us to cool them down. This is not without risk. It is entirely possible to fall out of an open window. Russia has a particularly bad problem with this. Many of Putin’s leading critics and rivals have died this way. To prevent this, building regulations mandate that all window sills are at least 1.1m high or alternatively use metal guards/balustrades of the same height. Doing the latter is expensive, so the end result typically looks something like this.

I suspect most people would prefer to live somewhere like the first property. The Building Regulations ‘experts’ at MHCLG disagree. I am told when Michael Gove attempted to change this – one departmental planner replied: “People think they want big windows, but they don’t.”

In theory, developers could meet the requirement by using air conditioning. But, air conditioning is only allowed as a last resort.

“The building should be constructed to meet requirement O1 using passive means as far as reasonably practicable. It should be demonstrated to the building control body that all practicable passive means of limiting unwanted solar gains and removing excess heat have been used first before adopting mechanical cooling. Any mechanical cooling (air-conditioning) is expected to be used only where requirement O1 cannot be met using openings.”

As a result, almost all new builds in Britain are built without air-conditioning.

National policy is hostile to AC (and I’d add: good design), but it could be worse. Britain is an anti-AC jurisdiction, but nowhere is more anti-AC than London.

In London, all major developments are forced to produce expensive heat modelling – even when they’re following Part O’s simplified approach. On top of this, there’s a requirement to maximise what’s known as dual-aspect. In layman’s terms, having windows on different walls to improve airflow.

The main reason why Part O is bad is that it produces ugly facades and less comfortable AC-less homes. The London Plan is bad in a different way: it doesn’t just make new homes ugly, it makes them smaller too.

The diagram below, from Centre for Cities’ excellent report ‘Breaking the Bottlenecks’, shows how the requirement to maximise dual aspect cuts internal floorspace for a given plot of land. The Centre for Cities cites data from Ireland, which showed that strict passive cooling requirements added €25,000 to the cost of building an apartment.

There’s another problem. The last Government stupidly brought in new building safety rules requiring all new buildings taller than 18 metres to have a second staircase. This is bad for many reasons–the Government’s own impact assessment suggested the policy’s costs outweigh the benefits by a factor 294–but one important reason is the way it interacts with the mandate to maximise dual aspect.

In fact, the building regulator’s own diagrams (reproduced by Centre for Cities) show how the easiest way to meet the second staircase requirement is in a slab building with a long hotel style-corridor. Yet dual aspect rules do not allow this type of construction. Taken together, dual aspect and two staircases sacrifice even more of a building’s floorspace.

Developers are, in effect, required to carry out extensive–and expensive–design tweaks to avoid installing air-conditioning. Yet, as the Centre for Cities notes, passive cooling has a hard ceiling. When outside temperatures climb above about 25 °C, the normal toolkit of shading, cross-ventilation and night-time “purge” airflow can no longer drag indoor temperatures down to comfortable levels. Opening windows at night or relying on daytime cross-flows only works when the air outside is cooler than the air you’re trying to expel. As a result, we’re seeing growing demand for inefficient mobile AC units and fans even in new-builds designed to maximise passive cooling.

The Greater London Authority recently consulted on scrapping the London Plan’s additional overheating rules and falling back on Part O instead. Increasingly, they recognise the dogmatic pursuit of dual-aspect is making it harder to build the homes London desperately needs.

This would be an improvement, but Part O is still an anti-AC document. Part O was developed under the assumption that electricity could never be low-carbon or abundant. It needs a rewrite. AC should no longer be considered a last resort to be avoided as much as reasonably practicable. It should be one of many options available to housebuilders to keep the homes they build at a comfortable temperature all year round. Developers should be free to sell homes with big windows and AC.

How energy efficiency rules discourage energy efficient cooling

Part O isn't the only bit of the building regulations that discourage the use of reversible air-to-air heat pumps. Energy efficiency standards also penalise air-to-air heat pumps.

From 2028, it will be illegal to let a property with an EPC rating of D or less. And that’s not the only reason to want a good EPC rating. Most borrowers offer cheaper mortgages for the most energy efficient homes worth around £500 a year for the average home.

The problem is installing an air-to-air heat pump, while keeping a gas boiler for hot water, can lead to a much worse EPC rating for three reasons.

1. Air-to-air heat pumps are treated as ‘secondary heating’. Only 10% of the house’s overall heating is credited to the cheaper to run heat pump. The rest is assumed to be gas.

2. Many air-to-air heat pumps aren’t included in the database used for assessing EPC ratings. As a result, they’re assumed to be around 3 times less efficient than they actually are.

3. It factors in a standard cooling load, but doesn’t account for the fact that in the future AC demand will correlate with cheap solar gluts.

And on top of all this, air-to-air heat pumps are penalised for the same reason all heat pumps are by the EPC system. It’s based not on emissions or costs for consumers, but ‘primary energy use’. What this means is using 1KWh of electricity is treated as 1.8.KWh of gas? This is a big problem when you remember that electrifying everything is at the core of Britain’s plan to cut carbon emissions.

There’s prospect for reform. In recent months, the Government has consulted on removing all three barriers to air-to-air heat pumps and changing the EPC metric from primary energy to one focused on cost and carbon emissions. Doing them should be a no-brainer and would end the absurd situation of consumers punished for making green choices.

Climate Realism

In recent years, it has felt as if politicians –Labour and Conservative alike– simply assumed the march to net zero was inevitable and that their job was just to pick the ‘best’ technologies. This was driven, in part, by the Climate Change Act, which requires five-year carbon budgets that set out technology changes in detail. In this vision of net zero, consumers were an afterthought.

Yet poll after poll makes clear, the public as a whole are up for climate action only so long as it doesn’t inconvenience them. In fact, I would go even further. People are naturally risk-averse. This isn’t a bad instinct, by the way, things often go wrong in unforeseen ways: just ask the people who are dealing with damp due to badly-installed insulation. The public will not make massive changes whether that’s swapping their petrol car for an electric one or ripping out their old gas boiler and replacing it with a heat pump unless it’s straight-forwardly better for them. Merely being ‘as good, but low-carbon’ won’t cut it.

Hairshirt environmentalism isn’t scalable. At best, it can persuade some of us to make symbolic, but ultimately pointless choices. Hitting net zero is simply not possible without consumers getting on board with electrification and ‘demand flexibility’ in a big way. Greening the grid may be hard technically, but it was surprisingly easy politically. Getting consumers to swap their boilers for heat pumps and switch to electricity tariffs where prices change every half hour will be an uphill battle.

Greens have been slow to realise this. In part, because they’re not normal. They hold views and values that are out of touch with the wider public. There’s nothing wrong with that per se. Many ‘out of touch’ views are later accepted as common sense. The problem is that when you want the public to make major lifestyle changes, you need an accurate picture of what they think, want, and fear.

What we need instead is policy driven by climate realism. Not just realism about climate science and the need for action but also realism about what consumers want. And on a 34 degree day, that’s air conditioning.