Nuo aurinkopaneelit ovat uusia.

Nuo means those.

A useful basic contrast is:

• nämä = these
• nuo = those
• ne = they in standard written Finnish

In everyday spoken Finnish, ne is very often also used where standard written Finnish would use nuo. So a learner may hear Ne aurinkopaneelit ovat uusia in speech, but Nuo aurinkopaneelit ovat uusia is the standard written form for Those solar panels are new.

Here is a breakdown:

• nuo = demonstrative pronoun/determiner, plural, nominative
  It points out the panels: those

• aurinkopaneelit = noun, plural nominative
  This is the subject: solar panels

• ovat = verb, present tense of olla (to be), 3rd person plural
  It matches the plural subject

• uusia = adjective uusi in the partitive plural
  It means new in a descriptive predicate construction

So the structure is basically:

Those solar panels + are + new

The ending -t marks the nominative plural.

The dictionary form is aurinkopaneeli = solar panel.
When you make it plural in the nominative, it becomes aurinkopaneelit = solar panels.

Compare:

• aurinkopaneeli = solar panel
• aurinkopaneelit = solar panels

Because the subject is plural, the verb is plural too: ovat.

Yes. Finnish very often uses compound words where English uses two separate words.

aurinkopaneeli is made from:

• aurinko = sun
• paneeli = panel

So literally it is something like sun-panel, but the natural English meaning is solar panel.

This is extremely normal in Finnish. The last part usually tells you the basic category of the word, so paneeli is the main noun here.

Because the subject is plural: nuo aurinkopaneelit = those solar panels.

The verb olla = to be changes like this in the present tense:

• on = is
• ovat = are

So:

• Aurinkopaneeli on uusi. = The solar panel is new.
• Aurinkopaneelit ovat uusia. = The solar panels are new.

In very casual spoken Finnish, people often use on even with plural subjects, but in standard Finnish this sentence correctly uses ovat.

This is one of the most common learner questions.

Uusia is the partitive plural of uusi. In sentences with olla (to be), a predicate adjective is often in the partitive plural when it simply describes a quality of plural things.

So:

• Nuo aurinkopaneelit ovat uusia. = Those solar panels are new.

This is the normal descriptive meaning.

If you used uudet, that would sound more like the new ones, or like you are identifying which panels they are, not just describing their condition.

A rough contrast:

• Ne paneelit ovat uusia. = Those panels are new.
• Ne paneelit ovat uudet. = Those panels are the new ones.

So uusia is the natural choice here.

Uusia is the partitive plural form of the adjective uusi = new.

Some useful forms are:

• uusi = new
• uutta = new (partitive singular)
• uudet = new (nominative plural)
• uusia = new (partitive plural)

In this sentence, the plural descriptive predicate uses uusia.

Not always in a simple one-to-one way.

When an adjective directly modifies a noun, they usually match very closely:

• uudet aurinkopaneelit = new solar panels

But in this sentence, uusia is not directly attached to the noun inside the noun phrase. It is a predicate adjective after ovat:

• aurinkopaneelit ovat uusia

Here, Finnish uses predicate rules, and that is why you get uusia instead of uudet.

So it is still connected to the plural subject, but it does not behave exactly like an attributive adjective would.

Because Finnish has no articles like English a/an and the.

Finnish usually expresses definiteness through:

• context
• word order
• demonstratives such as tämä, tuo, nuo
• possessive structures

So in this sentence, nuo already makes the reference specific: those solar panels.

Without nuo, the sentence Aurinkopaneelit ovat uusia could still mean The solar panels are new or just Solar panels are new, depending on context.

Yes, Finnish word order is more flexible than English word order, but not completely free.

The neutral order here is:

• Nuo aurinkopaneelit ovat uusia.

That is the most natural basic sentence.

You can change the order for emphasis or style, but then the focus changes. For example:

• Aurinkopaneelit ovat uusia.
  Neutral statement without those

• Uusia nuo aurinkopaneelit ovat.
  Marked/emphatic, something like New, those solar panels are

So for a learner, the safest pattern is:

demonstrative + noun + verb + predicate adjective

Yes.

That would still be a correct sentence:

• Aurinkopaneelit ovat uusia.

It means The solar panels are new or Solar panels are new, depending on the context.

Adding nuo makes the reference more specific and visible in the situation: those solar panels. So nuo is not required for grammar, but it adds pointing/deictic meaning.