The autumn equinox: what is it and what happens at that moment?

The equinox only occurs twice a year: once in March and once today, in September. The equinox is the moment when the Sun aligns with the Earth's equator, marking the start of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.

At that instant, day and night are almost equal in length. And while the Sun has kept us company for so many hours throughout the summer, from today onwards it becomes increasingly noticeable that daylight hours will get shorter, day by day.

When does the 2026 autumn equinox take place?

In Spain, the autumn equinox took place today, 23 September, at around 2:05 a.m. The exact time varies noticeably from year to year. According to forecasts from the National Geographic Institute, this was the exact moment in 2026 when the Sun aligned with the equator of our planet.

Why do the days get shorter so quickly starting today?

By around three minutes a day. That is approximately how much daylight we will lose in Spain during the autumn season, as a result of the Earth's tilt in relation to the Sun as it moves along its orbit.

Because of this axial tilt, Spain gradually moves further away from direct sunlight at this time of year, until the reverse process starts from the winter solstice in December, the shortest day of the year.

How your home's energy consumption shifts when autumn begins

Autumn is a transitional season when, barring unforeseen circumstances, the weather is milder than in summer and winter. Therefore, with some exceptions, energy consumption for heating and cooling has less of an impact on your electricity bill.

However, just as our position relative to the Sun changes, certain types of energy consumption in your home can also vary in different ways:

You switch on more lights for longer

As the days get shorter, we use electric lighting for longer. You'll need to switch the lights on to get ready before sunrise, and you'll rely on them for much of the afternoon when you get home.

The times when you use electricity also shift

As autumn sets in, running washing machines, tumble dryers, irons and dishwashers tends to be concentrated in the late afternoon. It now becomes more common to use these appliances when you get the chance, such as when you get home from work, or when you need to use them urgently, like preparing school clothes for the next day.

You spend more time at home

In general, autumn is rainier than summer. Spending the day outdoors becomes less appealing, making way for the season’s classic ‘sofa and blanket’ routine. As a result, we spend more hours watching TV, playing video games or browsing the internet. It also means spending more time in the kitchen, preparing stews that will once again make the hob and oven a more significant part of our monthly electricity bill.

Heating starts to come into play

Today's equinox heralds the arrival of shorter days, but also colder ones. Although heating will not be used as intensively as in the depths of winter, you will gradually need to turn it on. After so many months of disuse, this could be a good time to check that your system is ready for this time of year.

Electricity uses that become more significant in autumn

Fewer hours of daylight after the equinox: how much will your consumption increase?

According to the Institute for the Diversification and Saving of Energy (IDAE), households in Spain consume almost 6.5 million kWh a year on lighting alone. In other words, around 10% of our annual electricity bill.

However, this percentage varies by season. While during the summer solstice, which occurs around 21 June, we can enjoy up to 15 hours of free daylight a day, from now on, that figure will gradually fall to just 9 hours by the end of December. That's six additional hours of artificial lighting, with a corresponding impact on your bill from month to month.

The cost will depend on the type of light bulbs you use at home, as well as the type of tariff you have signed up for. As an example, we have calculated the impact using four 10 W LED bulbs and the current price of Endesa's Conecta Light Tariff:

* Calculations based on the price of €0.109/kWh for the Conecta Light Tariff as at 18 September 2026.

The first time you switch on the heating can have a significant impact on your bill

In summer, it was air conditioning and as winter approaches, heating will take over. These are the two most significant seasonal contributors to household energy consumption in Spain. In fact, according to IDAE studies, households spend more than twice as much on heating and cooling as they do on running washing machines.

Making sure your boiler and entire heating system are in good working order is therefore one of the best energy-saving measures you can start taking today. How to do it?

1. Check the condition of your boiler to prevent problems when you switch it on for the first time.
2. Check that the thermostat and its battery are working properly.
3. Check that the system's water pressure is within recommended levels.
4. Bleed the radiators to remove any air that may have built up inside them.
5. Run a first test before the weather gets colder.

MITECO's recommendations for saving on heating

On its website, the Ministry for the Ecological Transition and the Demographic Challenge (MITECO) suggests several very simple and inexpensive measures to help reduce the impact of heating costs on your bill during autumn and winter:

• Heat each room only to the level it actually needs.
• Turn off the heating when you leave home and save up to 20%.
• Air the whole house at once by creating draughts to speed up the process.
• Keep your radiators in good working order.
• Install programmable thermostats to manage consumption more effectively.

Does the arrival of autumn affect all households in the same way?

Within Spain, different climate zones can affect the energy needs of each household. For example, coastal areas will be more affected by ambient humidity than areas with a continental climate in central Spain. This can be reflected both in the effort required from your heating system and in greater demand for your tumble dryer.

Similarly, the loss of daylight hours tends to be more noticeable in north-western areas than in Mediterranean regions, as their latitude significantly reduces daily sun exposure. As a result, you'll need to use artificial lighting slightly more the closer you live to Galicia. 

But that's not the only factor that can affect your home's energy consumption in autumn. For example, a detached house or a rural property generally require more energy than an urban flat. At the same time, an older building in a city may be less efficient when it comes to heating and cooling than a traditional home in the countryside. Other factors also play a role, such as lifestyle habits, family size, the impact of working from home or, sometimes most importantly, the price of energy depending on the type of tariff you have signed up for.

How to tell whether you are actually using more energy each day

The truth is that changes in energy consumption during mild seasons such as autumn are not necessarily noticeable from one day to the next.

However, knowing how much electricity and gas you are using is always the first step towards using energy more efficiently. In other words, towards paying less. So, what is the best way to find out in practice?

Look at the kWh you use, not the amount in euros

The price of electricity and gas can vary, sometimes significantly, from one month to the next. That's because, while energy demand depends on the reasons we've discussed, generation costs also fluctuate due to various factors: gas market prices, their impact on electricity prices, conditions for generating solar and wind power...

Therefore, rather than comparing how much you have paid each month, the more reliable approach is to compare how much energy you have used: the amount of kWh.

Compare your October bill with your September bill

As it occurs at the end of September, the autumn equinox can provide a clear turning point for your energy consumption. A good way to check this is to analyse your bills for both months. Free tools such as Endesa's InfoEnergía can help you track the exact change for each appliance in your home.

Also compare it with your October bill from the previous year

This year-on-year comparison can help you identify whether any appliance is currently using more energy than usual. This might point to reduced performance or simply a change in your need to use it. But remember that the best approach is to compare kWh with kWh for the energy consumed, rather than the total amount you have paid.

If your habits change, it may be time to review your contract

There is one thing that makes this autumn equinox different: over the past few months, driven particularly by problems with international gas supply, energy prices have risen.

This makes keeping an eye on your household energy consumption increasingly advisable. Just as importantly, you should review the times when you use energy and how this affects what you pay under your current tariff:

Which tariffs to choose if you use more energy at night and at weekends this autumn

Electricity prices are generally more affordable at night and during the weekend. If these are the times when you use the most energy, you can benefit from cheaper off-peak periods with time-of-use tariffs, such as Endesa's Conecta 3 Periods.

Which tariffs offer more protection if you don't follow a set schedule

If, on the other hand, you run the washing machine and dishwasher whenever you get the chance, and weekends are taken up with other priorities, stable-price tariffs mean you don't have to worry about how electricity prices rise and fall throughout the day. Solutions include Conecta Light for new Endesa customers, as well as the Light 24h Online, Light 24h 3-years and Light 24h 5-years tariffs.

Which tariffs are best suited to the way you use energy at home?

Finally, for households where keeping control means knowing that you only pay for what you use, the personalised monthly fee offered by tariffs such as Endesa's Única Light provides peace of mind with a fixed monthly price and no unexpected costs.

Frequently asked questions about the equinox and energy consumption

When does autumn 2026 begin?

Autumn began today, 23 September, at around 2 a.m.

What happens during the autumn equinox?

The Sun aligns perfectly with the Earth's equator, marking the start of the autumn season.

Does the autumn equinox increase your electricity bill?

Not necessarily. At the beginning of autumn, some types of energy consumption may start to increase, such as heating and lighting, while others may decrease, such as air conditioning. It depends on each household's energy consumption.

What increases energy consumption most as the days get shorter?

Increased use of artificial lighting is the main driver. As daylight hours gradually decrease, we use the lights at home for longer each day. The lack of sunlight can also mean that we start switching on the heating on colder days, as we are also exposed to less warmth from the Sun.

Is energy consumption always higher in autumn than in summer?

No. Each season means higher or lower consumption for certain uses. In fact, average energy consumption in autumn tends to be lower than in summer as air conditioning use drops off, while temperatures are not yet cold enough to require heating every day.

When do the clocks change in autumn 2026?

At 3:00 a.m. on Sunday 25 October (2:00 a.m. in the Canary Islands). The clocks will be put back by one hour, meaning that Sunday will officially be one hour longer.

How do I know whether my energy consumption is changing because of autumn?

Compare your October bill with your September bill and focus on how many kWh you have used. You can also check the differences in consumption for each appliance in your home using tools such as Endesa's InfoEnergía.

Which has a greater impact on energy costs: lighting or heating?

Lighting at the beginning of autumn, as the days are shorter and it is generally not yet cold enough to switch on the heating. As autumn progresses, heating will account for an increasing share of energy expenditure.