En cuanto empieza el frío, encendemos la calefacción y el radiador del dormitorio se calienta enseguida.

En cuanto means as soon as or once.

So:

• En cuanto empieza el frío = As soon as the cold starts / Once the cold weather begins

It introduces the moment when the main action happens.

A few similar expressions are:

• cuando = when
• apenas = as soon as, hardly had
• tan pronto como = as soon as

In this sentence, en cuanto sounds very natural for talking about something that happens immediately after a change in weather.

Spanish often uses nouns where English prefers a different structure.

Here, el frío literally means the cold, so:

• empieza el frío = the cold begins

In natural English, we would usually say:

• it starts getting cold
• the cold weather starts
• the cold sets in

So this is a good example of Spanish expressing an idea in a way that sounds more noun-based than English.

Also, el frío here refers to cold weather in general, not just the abstract idea of coldness.

Spanish often uses the definite article more than English does, especially with general concepts, weather-related nouns, and body parts.

So el frío does not necessarily mean a specific cold; it can simply mean the cold weather as a general seasonal condition.

Compare:

• Me gusta el calor. = I like hot weather / heat.
• No soporto el frío. = I can’t stand cold weather / the cold.

In English, we often drop the article in these cases, but in Spanish it is usually required.

It is in the present tense because the sentence describes a habitual action or something that regularly happens.

• En cuanto empieza el frío, encendemos la calefacción...
• As soon as the cold starts, we turn on the heating...

Spanish often uses the present tense for routines, general truths, and repeated situations, just like English can:

• When winter comes, we stay inside more.
• As soon as it gets cold, we turn on the heating.

So this is not necessarily about one single moment happening right now; it is about what usually happens.

Yes. Encender means to light, to switch on, or to turn on, depending on context.

Here:

• encendemos la calefacción = we turn on the heating

Other examples:

• encender la luz = to turn on the light
• encender la televisión = to turn on the TV
• encender un cigarrillo = to light a cigarette

In Spain, encender is very common for devices, lights, heating, and anything that gets activated.

La calefacción usually means the heating or the heating system.

So:

• encender la calefacción = to turn on the heating

It does not usually mean a single heater unit. It often refers to the home’s heating as a system in general.

Related words:

• la calefacción central = central heating
• la calefacción de gas = gas heating
• la calefacción eléctrica = electric heating

In this sentence, it refers to the heating system being switched on, which then causes the radiator to warm up.

Del dormitorio means of the bedroom or, more naturally in English, the bedroom radiator.

So:

• el radiador del dormitorio = the radiator in the bedroom / the bedroom radiator

Spanish often uses de + noun where English prefers a noun used as an adjective.

Compare:

• la puerta del coche = the car door
• la ventana del salón = the living-room window
• el radiador del dormitorio = the bedroom radiator

You could say el radiador en el dormitorio, but that focuses more on location: the radiator in the bedroom.
Del dormitorio sounds like the normal way to identify which radiator we mean.

Del is a contraction of:

• de + el = del

So:

• el radiador del dormitorio literally comes from
• el radiador de el dormitorio

But Spanish does not keep de el in normal usage; it contracts to del.

This happens only with de + el:

• de el → del
• a el → al

Examples:

• la puerta del baño = the bathroom door
• voy al mercado = I’m going to the market

Note: this contraction does not happen if El is part of a proper name:

• de El Escorial stays de El Escorial

Yes, this is the verb calentarse, which literally means to warm up / to get warm.

So:

• el radiador se calienta = the radiator warms up / gets warm

This is a very common use of reflexive-style verbs in Spanish to describe a change of state:

• se enfría = it cools down
• se seca = it dries
• se rompe = it breaks
• se derrite = it melts

In English, we usually just say gets warm or warms up.
Spanish often uses se + verb for this kind of process.

It does not mean the radiator is deliberately heating itself. It just means it becomes warm.

Yes, but the meaning changes.

• El radiador se calienta = The radiator gets warm / warms up
• El radiador calienta el dormitorio = The radiator heats the bedroom

So:

• calentarse = to become warm
• calentar algo = to heat something

That is an important difference:

• La sopa se calienta. = The soup gets warm.
• Caliento la sopa. = I heat the soup.

In your sentence, the radiator itself is changing temperature, so se calienta is the natural choice.

Enseguida means right away, very quickly, or immediately/soon after, depending on context.

Here:

• se calienta enseguida = it warms up right away

It suggests that once the heating is turned on, the bedroom radiator gets hot very fast.

Other common adverbs with similar meanings:

• rápidamente = quickly
• inmediatamente = immediately
• al momento = right away

Enseguida is very common in everyday Spanish and often sounds more natural and conversational than inmediatamente.

Because Spanish often uses the present tense to talk about:

1. habits
2. general truths
3. future actions in time clauses, especially after words like cuando, en cuanto, apenas, etc.

In this sentence, the main idea is habitual:

• As soon as cold weather starts, we turn on the heating...

But even when referring to the future, Spanish often keeps the present after en cuanto:

• En cuanto llegue / llega el invierno...
• As soon as winter arrives...

For a repeated seasonal action, the present tense sounds completely normal.

Not exactly, though they can overlap.

• dormitorio = bedroom
• habitación = room, and sometimes bedroom depending on context

In Spain:

• el dormitorio clearly means the room used for sleeping
• la habitación can mean room in general, but in many contexts it can also mean bedroom

So here, el radiador del dormitorio specifically means the bedroom radiator.

If the sentence used habitación, it could still be understood, but dormitorio is more precise.

Because Spanish usually drops subject pronouns when the verb ending already shows who the subject is.

• encendemos already means we turn on
• so nosotros encendemos is usually unnecessary

The ending -emos tells you the subject is we.

Spanish only adds the pronoun when it is needed for emphasis, contrast, or clarity:

• Nosotros encendemos la calefacción, pero ellos no.
• We turn on the heating, but they don’t.

In your sentence, there is no need to say nosotros.

It sounds natural and idiomatic in Spain.

A speaker from Spain would readily understand:

• En cuanto empieza el frío = as soon as cold weather begins
• encendemos la calefacción = we turn on the heating
• el radiador del dormitorio se calienta enseguida = the bedroom radiator warms up right away

A few small variations might also be common, for example:

• En cuanto empieza a hacer frío...
• Cuando llega el frío...

But the original sentence is perfectly natural Spanish, especially in a context where people are talking about heating at home.