Learn Hardcore Swedish: Om han inte kan reparera den, köper vi en ny nästa sommar. - If he cannot repair it, we will buy a new one next summer.

If you start the sentence with something other than the subject (here, the om‑clause), the verb in the main clause must still be in second place. The whole first clause Om han inte kan reparera den counts as position 1, so:

Om han inte kan reparera den, köper vi en ny nästa sommar.
(Clause = position 1, köper = position 2, vi = position 3)

If you put the main clause first, normal order returns:

Vi köper en ny nästa sommar om han inte kan reparera den.

Why is it han inte kan and not han kan inte?

Because om han inte kan reparera den is a subordinate clause (introduced by om).

In Swedish:

In main clauses, the verb is in second place and inte comes after the verb:
- Han kan inte reparera den. – He cannot repair it.
In subordinate clauses, the word order is different: subject – sentence adverb (like inte) – verb:
- … att han inte kan reparera den
- Om han inte kan reparera den …

So han inte kan is the correct subordinate-clause order.

Why are kan and köper in the present tense if the action is in the future?

Swedish often uses the present tense to talk about the future when there is a time expression that makes the time clear, like nästa sommar.

Om han inte kan reparera den, köper vi en ny nästa sommar.
= If he cannot repair it, we will buy a new one next summer.

You can also use a future construction:

… ska vi köpa en ny nästa sommar.

But the simple present with a future time expression is very natural and common in Swedish.

Could you also say ska vi köpa en ny instead of köper vi en ny?

Yes:

Om han inte kan reparera den, ska vi köpa en ny nästa sommar.

This explicitly marks the future (similar to English will).
The difference is small in meaning:

köper vi – neutral, often used for planned or expected future when time is clear
ska vi köpa – slightly more explicit about intention/plan, like are going to buy / will buy

Both are correct here.

Why is it om and not när at the start?

om = if, used when you are not sure whether the condition will be fulfilled.
när = when, used when you expect something will definitely happen (or happens regularly).

Here, it’s uncertain whether he will be able to repair it, so om is correct:

Om han inte kan reparera den, köper vi en ny … – If he cannot repair it…

If you said:

När han inte kan reparera den, köper vi en ny …

it would sound like you are assuming as a fact that he will not be able to repair it.

What is the difference between reparera, laga, and fixa?

All can be translated as to repair / fix, but they differ in style and typical use:

reparera – more formal/technical, often used for machines, cars, electronics, etc.
- reparera bilen, reparera datorn
laga – more everyday and general:
- laga cykeln – fix the bike
- laga maten – cook (literally prepare/fix the food)
fixa – very colloquial, like to fix / sort out:
- Han kan fixa den – He can fix it.

In your sentence, reparera sounds slightly more formal/neutral and is very natural if “it” is some kind of device or machine.

Why is it kan reparera and not just reparerar?

kan expresses ability or possibility (can in English):

Om han inte kan reparera den … – If he cannot repair it…

If you say:

Om han inte reparerar den …

this is more about whether he does the action or not (e.g. if he refuses or forgets), not whether he is able to. So kan focuses on his ability or skill.

Why is it den and not det in reparera den?

den and det are object pronouns that replace a previously mentioned noun:

den replaces an en-word (common gender):
- en cykel → reparera den
- en bil → reparera den
det replaces an ett-word (neuter gender):
- ett hus → reparera det
- ett bord → reparera det

So den tells you that the thing being repaired is an en-word noun (like en bil, en dator, en maskin, etc.).

Why is it en ny and not something like en ny en for “a new one”?

In Swedish, you normally just say:

en ny (for en-words)
ett nytt (for ett-words)

The noun is understood from context:

Om han inte kan reparera bilen, köper vi en ny.
– If he can’t repair the car, we’ll buy a new one.

You don’t add a second en at the end (en ny en is not standard Swedish in this sense).

Why is there no preposition, just nästa sommar and not i nästa sommar?

With nästa and förra in time expressions, Swedish normally does not use a preposition:

nästa sommar – next summer
förra veckan – last week
nästa år – next year

You do use i with bare time nouns:

i sommar – this summer
i morgon – tomorrow
i år – this year

So nästa sommar is the natural form; i nästa sommar sounds wrong.

Is the comma before köper necessary?

Yes, it is standard (and recommended) to put a comma between a subordinate clause that comes first and the following main clause:

Om han inte kan reparera den, köper vi en ny nästa sommar.

If the main clause comes first, a comma is usually not used:

Vi köper en ny nästa sommar om han inte kan reparera den.

So the comma here follows normal Swedish punctuation rules.

Can I put the main clause first, and does anything else change?

Yes, you can switch the order:

Vi köper en ny nästa sommar om han inte kan reparera den.

The word order inside each clause stays the same:

Main clause: Vi köper en ny nästa sommar (subject–verb)
Subordinate clause: om han inte kan reparera den (subject–inte–verb)

Only the comma and the inversion (köper vi vs vi köper) change, depending on which clause you place first.

How would this sentence change if the object were an ett-word instead?

Two things would change:

The pronoun den → det
The implied “new one” en ny → ett nytt

Example with ett hus (a house):

Om han inte kan reparera huset, köper vi ett nytt nästa sommar.
– If he can’t repair the house, we’ll buy a new one next summer.