Elegimos la tarifa eléctrica con el comparador de ofertas.

Elegimos is the 1st person plural form of elegir (to choose).

It can mean either:

• we choose (present tense)
• we chose (preterite / simple past)

So this form is ambiguous on its own. Context tells you which meaning is intended.

Examples:

• Hoy elegimos la tarifa eléctrica. = Today we choose the electricity tariff/plan.
• Ayer elegimos la tarifa eléctrica. = Yesterday we chose the electricity tariff/plan.

Because Spanish often drops subject pronouns when the verb ending already makes the subject clear.

• Elegimos already tells you the subject is we
• So Nosotros elegimos... is possible, but usually unnecessary

You would add nosotros mainly for:

• emphasis
• contrast
• avoiding confusion

For example:

• Nosotros elegimos la tarifa eléctrica, no ellos. = We chose the electricity plan, not them.

Spanish uses articles more often than English does.

Here, la tarifa eléctrica means:

• the electricity tariff
• the electricity rate
• the electricity plan

The definite article la suggests a specific tariff/plan, or the one being discussed in context.

In English, we might sometimes say:

• We chose an electricity plan
• We chose the electricity plan

But in Spanish, using la is very normal when referring to the item selected or under discussion.

Tarifa eléctrica usually refers to the electricity pricing plan/rate/tariff offered by an energy company.

Depending on context, English translations could be:

• electricity tariff
• electricity rate
• electricity plan

It does not usually mean the bill itself.

Compare:

• tarifa eléctrica = the pricing plan/rate
• factura de la luz = the electricity bill
• precio de la electricidad = the price of electricity

In Spanish, most descriptive adjectives normally come after the noun.

So:

• tarifa eléctrica = electric tariff / electricity tariff

Also, eléctrica agrees with tarifa:

• tarifa is feminine singular
• so the adjective is eléctrica, also feminine singular

Compare:

• tarifa eléctrica
• servicio eléctrico
• ofertas eléctricas

Because adjectives in Spanish must agree in gender and number with the noun they describe.

Here:

• tarifa is feminine singular
• so the adjective must be eléctrica

If the noun were masculine, you would use eléctrico:

• el sistema eléctrico

If it were plural:

• las tarifas eléctricas

Here con means with, but in natural English it often corresponds to:

• with
• using
• by means of

So:

• Elegimos la tarifa eléctrica con el comparador de ofertas.

can be understood as:

• We chose the electricity plan with the comparison tool
• We chose the electricity plan using the offer comparison tool

Spanish often uses con to show the tool or means used to do something.

Yes, it could.

For example:

• Elegimos la tarifa eléctrica usando el comparador de ofertas.

That means essentially the same thing:

• We chose the electricity plan using the comparison tool

But con is often shorter and very natural when talking about an instrument or tool.

So both work, but con is very common and idiomatic here.

Comparador de ofertas means something like:

• offer comparison tool
• deal comparison tool
• comparison website for offers
• comparison engine for deals/plans

It refers to a tool, website, or app used to compare different offers.

In this phrase:

• comparador = comparator / comparison tool
• de ofertas = of offers / for offers

So the full idea is a tool for comparing offers.

Spanish often connects nouns with de where English might use:

• a noun + noun structure
• for
• of

So:

• comparador de ofertas literally = comparator of offers
• natural English = offer comparison tool

This is a very common pattern in Spanish:

• tarjeta de crédito = credit card
• compañía de seguros = insurance company
• comparador de precios = price comparison tool

Because the comparison tool is comparing multiple offers, not just one.

So:

• oferta = offer / deal
• ofertas = offers / deals

A comparador de ofertas is designed to look at several options and help you choose among them.

Yes, it is natural and understandable in Spain.

That said, depending on context, people might also say things like:

• Elegimos la tarifa de la luz con un comparador de ofertas.
• Elegimos la tarifa eléctrica con un comparador.
• Elegimos la tarifa con un comparador de tarifas.

A small nuance:

• comparador de ofertas focuses on comparing offers/deals
• comparador de tarifas focuses more specifically on comparing tariffs/rates/plans

So your sentence is good, but there are other very natural versions too.

The given word order is normal:

• Elegimos la tarifa eléctrica con el comparador de ofertas.

But Spanish can sometimes move parts around for emphasis.

For example:

• Con el comparador de ofertas, elegimos la tarifa eléctrica.

This puts more emphasis on how the choice was made.

The most neutral version is the original one:

• Verb + object + prepositional phrase

Normally, no. In this context, con el comparador de ofertas is understood as using the comparison tool, not together with it.

Spanish con can sometimes mean simple accompaniment, but here the meaning is clearly instrument/method because a comparador is a tool, not a person accompanying you.

So the natural interpretation is:

• We chose the electricity plan using the offer comparison tool.