It is a very important question, which will depend on two main factors. The first is the model we have, and the second is its years, since the price to replace it will be different, but above all, whether it is worth doing so or not.
Change a Mac battery?
The first thing we should do is look at the battery replacement costsince depending on the model it will have one price or another, yes, it is always advisable to do it directly through the official Apple support, since, in other places, it will be much cheaper, but it has too many disadvantages and the remedy could be worse than the disease.
If we decide on the official website, we have a link where we can see the price of each repair. A MacBook Air from 2015, which costs 185 euros, will not be the same as a MacBook Pro M3 from 2023, which will cost us 289 euros.
This in turn is related to the price of the equipment, since, obviously, a 1,000 euro Air computer cannot be worth almost 300 euros per battery, since there would be no doubt that it is not profitable. However, if the new computer is worth 2,500, then paying 289 is not such a bad investment.
That is, we will have to see the percentage of the cost with respect to the equipment we have. If this exceeds 20%, and it is already more than 5 years old, I do not think that changing the battery is a good option. However, if it is around 10% or 15% and you have not yet reached that age, it would make no sense to buy a new Mac, since we would be wasting money.
Now, also It will depend on its useful life, it is not the same that it no longer lasts at all and we have to continually charge it, than that it has been reduced by half. With 6 hours of battery life, instead of 12, I wouldn't change it either, unless I need to take it with me for an entire work day and I'm looking for that maximum autonomy.
In summary, it will depend a lot on each case, however, and As a general rule, if the equipment is less than 5 years old and we give it a lot of effort, don't hesitate, it will be very profitable for you to have a new battery. In addition, you will not only improve the autonomy, but also its performance, since a worn battery can affect it, not only at power levels.
However, if your Mac is already more than 5 years old and the cost is about 200 euros, it is still better to continue using it with a cable, waiting to purchase another one later, or even sell this one for someone who does want to make the change and have , for little money, a new Mac.