Well, here we are. The UK has decided to have an actual summer for once (with some predicted record temperatures), and while that’s great, it does come with a set of challenges for anyone who cares about fuel efficiency or EV range. Heat is not your car’s friend, and it is not your wallet’s friend either.
Whether you drive a petrol, diesel, hybrid or electric car, the heat affects you differently but it affects everyone. Here is everything you need to know to get through a hot UK summer without your fuel bill or your EV’s diminishing range ruining your day.
The Problem With Heat and Cars
Before we get into the tips, it helps to understand what is actually happening when temperatures climb.
In a petrol or diesel car, heat increases tyre pressure, thickens the fuel and puts extra load on the cooling system. The bigger issue is what most drivers do in response to heat: they blast the air conditioning. Air conditioning is an engine-driven compressor. It puts a real load on the engine and costs real fuel. In a typical petrol car, air conditioning can reduce fuel economy by up to 10 percent. On a hot motorway with the air con running flat out, that cost is measurable at the pump. With fuel prices at record levels, is being cool actually worth it?
In an electric car the picture is a little different, and there is genuinely good news in it. EVs are so efficient that they produce far less waste heat than a petrol engine, which means the air conditioning does not have to work as hard against residual engine heat to keep the cabin cool. That is one real advantage EVs have over petrol cars in summer that rarely gets mentioned.
That said, cooling an EV cabin in hot weather typically costs around 5 to 15 percent of range, and in extreme heat the battery cooling system also draws power to protect the pack, adding to the total drain. On a modest battery like the one in my Volvo EX30, 15 percent is a meaningful chunk of range, especially when you’re already disappointed by its range overall.
Electric cars perform optimally between 20 and 25 degrees Celsius, with range potentially dropping by up to 15 percent when temperatures exceed 35 degrees. We do not often hit 35 degrees in the UK, but in a heatwave we do.
The other thing worth flagging for EV drivers: at higher speeds, aerodynamic drag has a far greater effect on range than cabin cooling. Dropping from 70mph to 60mph can add 10 to 20 percent more range. In summer, limiting speed is still the single biggest lever you have, even ahead of the air conditioning.
What Hot Countries Do Differently
If you want to understand how to deal with heat and cars, it helps to look at places where this is not an occasional problem but a daily reality.
In the UAE and Saudi Arabia, where summer temperatures routinely hit 45 to 50 degrees, drivers treat their cars very differently to how most of us do here. Drivers in Dubai are advised to vent hot air by opening windows briefly before switching the air conditioning on, set climate control to a moderate 20 to 22 degrees, and consider window tinting to block solar heat and reduce the need for high air conditioning output.
Finding shaded parking is treated as a serious daily priority, not an afterthought, and tyre pressure monitoring is considered essential because hot roads and hot air cause pressure to fluctuate in ways that cost both safety and efficiency.
Drivers routinely leave car doors open for 15 to 20 seconds before getting in to allow trapped hot air to escape, use specialist reflective windscreen shields as a matter of course, and leave windows slightly cracked when parked to allow air circulation.
Most of these habits cost nothing. They just require thinking about the car as something that needs managing in the heat, not just something you get into and drive. That mindset shift is the most useful thing to take from hot-country driving culture.
Summer Tips for Petrol and Diesel Drivers
Use recirculate mode on the air conditioning. When you first get in a hot car, set the air con to draw in outside air to flush out the heat quickly. Then switch to recirculate, which cools the air already inside the cabin rather than continuously pulling in warm air from outside. You will cool the car faster and the system works less hard.
Below 40mph, open the windows instead. At lower speeds the aerodynamic drag from open windows is minimal. On a short town journey at 30mph, open windows cost you almost nothing in fuel and save you the full air conditioning load. Above 50mph, close them and use air con sparingly.
Park in the shade and think about where the sun will be when you leave. A shaded spot in the morning can be full sun by 5pm. Two minutes of thought when you park can save you getting into a car that feels like a sauna and needing to blast the air conditioning for the first ten minutes of the drive home.
Use a windscreen sunshade. The ones you fold out across the dashboard work. A parked car in direct sun can reach 60 to 70 degrees inside within an hour. A reflective sunshade keeps the cabin significantly cooler, which means less energy required to cool it when you return, and less strain on the air conditioning in the first few minutes of driving.
Dress appropriately. This sounds obvious but it makes a real difference. A light shirt means you need far less air conditioning to be comfortable than you would in office clothes on a hot day. If you are commuting, keep a spare shirt and change when you arrive.
Check tyre pressures more often. Heat increases tyre pressure. An over-inflated tyre in summer heat wears unevenly and affects handling. Check pressures when cold and adjust to the manufacturer’s recommended range. Under-inflated tyres cost you fuel. Over-inflated tyres in heat can become a safety issue.
Travel at cooler times. Early morning is the most efficient time to drive in summer. Roads are quieter, ambient temperature is lower so the air conditioning works less hard, and the engine runs more efficiently. If you can avoid driving at peak heat in the afternoon, your fuel figures will show it.
Service your air conditioning system. A poorly maintained system works harder than it needs to and costs you more fuel. If it is blowing warmer than it used to, or takes a long time to cool the cabin, get it checked. A regas typically costs £50 to £80 and can make a meaningful difference to both comfort and efficiency.
Summer Tips for EV Drivers
Pre-condition the car while it is still plugged in. This is the single most important summer tip for EV owners and the one most people ignore. If you pre-condition the cabin to a comfortable temperature before you unplug, you are using grid electricity to cool the car rather than battery power. You set off with a full battery and a cool cabin rather than depleting the battery to cool a hot interior in the first ten minutes of driving. Most EVs let you set this up via the app or a scheduled departure time.
If your EV has a heat pump, make sure it is enabled. A heat pump moves heat from outside air rather than generating cooling directly from battery power. In summer it means the air conditioning runs more efficiently and draws less from your range. My EX30 does not have a heat pump, which combined with the lack of seat ventilation makes hot days a proper trade-off between comfort and range. If you are buying an EV and live somewhere that gets genuinely hot summers, a heat pump is worth paying extra for. We cover exactly why in our EV Heat Pump FAQ.
Avoid charging to 100 percent and leaving the car in full sun. Chronic high heat is tough on batteries over time. Park in shade or a garage when you can to slow long-term degradation. This matters more over years than days, but it is a habit worth building.
Avoid DC fast charging in peak heat where possible. Fast charging generates more heat within the battery pack. When temperatures are already warm, slower charging is kinder to the battery long-term. If you are topping up at home overnight, this is not an issue. If you are using a rapid charger on a hot afternoon, try not to make it a daily habit.
Use seat ventilation over cabin air conditioning if your car has it. Ventilated seats cool the person directly and cost a fraction of the energy required to cool the entire cabin. My EX30 does not have it, which is a frustration on very hot days, but if your car does, use it.
Keep regen settings high in urban driving. In summer stop-start traffic, high regen is especially valuable because you are recovering energy at every deceleration rather than wasting it. With the air conditioning also running, keeping regen maximised helps offset the additional drain. Full guide to getting the most from regen in our Regenerative Braking guide.
Add a range buffer on very hot days. In extreme heat, add a 10 to 15 percent state of charge buffer above what your route planner suggests. That covers air conditioning use, traffic and any unexpected detours without stress.
Open windows at low speeds rather than using air con. At 30mph through a town, windows down is essentially free in range terms. Air conditioning at the same speed is taking meaningful energy from the battery. Same principle as petrol cars, but more important here because the drain is direct.
What About Battery Degradation in Heat?
High temperatures do accelerate long-term battery degradation, but the effect in UK conditions is modest. We are not in Dubai or Australia (although I wish I was in Oz!). Our summer heatwaves last days to weeks, not months.
The practical precautions are straightforward: park in shade where you can, do not leave the car sitting at 100 percent charge in full sun for days at a time, and let the battery cool before rapid charging if you have been driving hard in hot weather. Modern EVs have thermal management systems that handle most of this automatically, but being aware of it means you are not adding unnecessary stress to the pack.
If you are considering a used EV purchase, an LFP battery (lithium iron-phosphate LFP) is worth seeking out. LFP chemistry degrades less in heat than standard lithium-ion. Our Golden Time to Buy a Used EV guide covers what to look for in more detail. If you’re unsure about which EVs have blade batteries, the BYD range using their blade battery technology uses LFP.
The Summer Checklist
Before any long summer journey in any car: check tyre pressures cold, check the screen wash is topped up, make sure the air conditioning is working properly before you need it on a motorway, and keep water in the car for yourself.
For EV drivers: set a scheduled departure with pre-conditioning on, add a range buffer to your planned route, and check the battery health status in your car’s app if it shows one.
None of this is complicated. Heat is manageable with a bit of thought. Keep the speed sensible, the air conditioning on a moderate setting, and the windows down in town, and summer driving does not have to cost you significantly more than any other time of year.
Stay cool out there. I am not a fan of the heat and I’m doing everything I can to minimise its effects on my body and range. I’ve even started coming into the office a little earlier so I can beat the morning sun and get the office aircon working in advance of the hot days.
Let’s hear from you
How are you coping in the heat behind the wheel? What are your summer hypermiling / fuel saving tips. Let us know in the comments.
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