Together with the introduction of summer working hours across the entire week, working from home during July and August has become an increasingly popular option among Spanish companies.

Its benefits include a better work–life balance once the school holidays begin, as well as the extra free time gained by not having to commute every day.

In addition, depending on the working arrangement, Spain's Law 10/2021 on Remote Work sets out the possibility for employers to reimburse employees for certain costs associated with working from home. These costs may include, among other things, the additional electricity consumed at home.

If you're wondering how much working from home in summer increases your electricity consumption, let’s take a closer look at how much is actually due to working remotely and how much is really linked to keeping cool while you work.

The biggest cost of working from home in summer: air conditioning

Especially if you've spent the rest of the year working in the office and only switch to working from home during the summer months, your first question is probably: How much will running my computer impact my electricity bill?

It's a great question. In reality, though, its consumption is very low. If we do the maths, based on an eight-hour working day and an electricity price of €0.128 per kWh, such as Endesa's Light 24h Tariff, a typical 100 W laptop consumes just over €0.10 worth of electricity per day.

The question is whether you are willing to work for those eight hours in temperatures above 30°C, or whether you’d rather do so at a comfortable 25 or 26°C thanks to air conditioning. Because, in reality, cooling is the main source of electricity consumption when you work from home.

Using a 1,500 W air conditioning unit to keep the heat at bay can increase your electricity costs by up to 15 times compared with running your computer, adding more than €1.50 to your bill for each eight-hour working day. That is more than €30 a month, compared with the barely €2 spent on running a laptop.

Of course, it all depends on the devices you use to work from home, how you use them and your current tariff. And there is a formula you can use to calculate exactly how much electricity you will actually use this summer.

How to calculate how much electricity you use when working from home

The formula for finding out how much electricity you will use and how much it will cost is very simple:

1. Check the power consumption in watts (W) of the devices you will be using. You can do this by checking the instruction manual or, for greater accuracy, by connecting a power meter to the socket used by each device.
2. Divide the figure by 1,000 to find out how much electricity each device uses during one hour of normal operation.
3. Multiply the result by the number of hours each device will be switched on during your working day.
4. Finally, add all the figures together and multiply the total by the price per kWh on your electricity bill.

This formula will give you a fairly accurate idea of how much you will pay for working from home. However, the final impact on your bill will not be the same for everyone, as it depends on the equipment each person needs for their work and to carry it out comfortably. In areas with milder temperatures, for example, cooling will cost less, while it may result in higher costs in large, open-plan homes.

Tell me how you work from home and I’ll tell you how much electricity you use

So, we have established that cooling is the main factor when it comes to working from home, followed by your computer, fan and other smaller sources of consumption, such as your router, lighting or the occasional trip to the fridge.

They will have a greater or lesser impact on your electricity bill depending on how you combine them. To give you a rough idea, we have prepared two examples based on two possible scenarios:

Working from home in summer with a laptop and a fan.

Laptops use less energy than desktop computers with separate monitors, with the difference ranging from 50% to 85% depending on the case. Your consumption also depends on the type of applications you use. Office software requires very little energy, while video calls, design applications and video editing software require considerably more.

Fans follow a similar pattern: a USB fan for personal use consumes just 0.005 kWh, while more powerful plug-in models can exceed 0.07 kWh.

How much could each device add to your monthly bill if you work 160 hours?