Comparing electricity offers and spotting traps

Terms used

• CNMC — The CNMC is Spain's national markets and competition regulator, which runs the official electricity offer comparator.
• 2.0TD — The 2.0TD is the standard tariff access type for most households with contracted power up to 15 kW.
• CUPS — The CUPS is the code that identifies your supply point, shown on your bill and in your contract.
• PVPC — The PVPC is the regulated electricity tariff, with prices linked to the wholesale market, used as a reference for comparison.
• Permanence — A permanence clause is a minimum-stay requirement in a contract, usually with a penalty if you leave early.

Key rules

• Compare total cost: Judge each offer by its estimated annual cost and its conditions, not by the price per kWh.
• Official tool: Use the CNMC comparator, and treat its result as an estimate, not a guarantee.
• Withdrawal: If you sign at your door, by phone or online, you can withdraw within 14 days.
• Extras: Refuse add-ons you did not ask for, such as maintenance or insurance.

Compare the yearly cost, not the headline price

A low price per kWh tells you little. What matters is the estimated cost for a full year, plus the conditions attached. Use the official comparator, then read the contract terms before you sign.

Use the official comparator

The CNMC, Spain's energy and competition regulator, runs a free comparison tool called Comparador de ofertas de energía. Its web address and layout can change, so search for "CNMC comparador ofertas energía" and open the official result.

You will need:

• your postcode
• your tariff access type, which is usually 2.0TD for households
• your contracted power
• your yearly consumption by period, or your CUPS to import it

Your latest bill shows these details. The tool then lists offers with an estimated annual cost, price details, and conditions such as duration, permanence and extras.

Keep two limits in mind. The cost is an estimate based on what you entered. The list also covers only offers that suppliers have registered. The supplier's contract is what binds you, so the comparator does not replace reading it.

If you want to test different usage levels, the calculator below helps you estimate your annual cost under different offers.

Compare against the regulated tariff

The PVPC is the regulated tariff, and it works as a reference point. If a free-market offer is not clearly cheaper over a year, or its conditions are worse, you have little reason to take it.

What the supplier must tell you before you sign

You should get clear information on:

• who the supplier is and how to contact them
• the price, with energy and power terms, taxes and charges shown separately
• the contract duration and any renewal
• any permanence clause and its penalty
• how you can cancel or change the contract
• how you pay and how you are billed
• how to complain

The contract must also state how and when the price can be revised. It must show your CUPS and contracted power. If any of this is missing or vague, ask in writing before you sign.

Traps to look for

• Prices that rise. A cheap start can jump after a few months. Fixed prices are often revised when the term ends.
• Permanence and penalties. A minimum stay with an exit fee can lock you into a poor deal.
• Price changes during the contract. Some contracts let the supplier change the price with notice.
• Extras. Maintenance, insurance, gas or boiler services can be added to your bill. Decline anything you did not ask for.
• "Free" energy. It can come with a higher power charge, so the yearly total can end up higher.
• Indexed prices. They can look cheap but follow the market and vary from month to month.
• Doorstep and phone sales. Never agree to anything you do not fully understand. Contracts signed at your door or by phone or online can be withdrawn within 14 days.

The checklist and warnings below go through these steps in order.

Checklist

• Search for the CNMC comparator, Spain's official electricity offer comparison tool, and open it.

• Enter your postcode, tariff access type (usually 2.0TD for households) and contracted power.

• Enter your yearly consumption by period, or enter your CUPS (the supply point code on your bill) to import it from the distributor.

• Compare the estimated annual cost of each offer, not the headline price.

• Check each offer's duration, permanence (minimum-stay) clause and exit penalty.

• Check whether the price rises after a few months or when a fixed term ends.

• Check that the offer shows energy and power terms, taxes and charges separately.

• Compare the offer against the regulated PVPC tariff.

• Decline any unrequested extras such as maintenance, insurance, gas or boiler services.

• Check that the contract states the conditions for price revision, your CUPS and your contracted power before you sign.

What to watch out for

• Low starting prices that rise: Some offers start cheap and rise after a few months, or fixed prices get revised when the term ends. Compare the full annual cost and ask what the price will be after the first months or at renewal.

• Permanence clauses and penalties: A minimum-stay clause can charge you a penalty if you leave early. Read the duration and penalty terms before signing, and ask for them in writing.

• Unrequested extras: Maintenance, insurance, gas or boiler services can be added to your bill. Decline add-ons you did not ask for and check the bill's extra lines.

• 'Free' energy and indexed prices: A 'free' energy offer can raise the power charge, and an indexed price can look cheap but vary with the market. Judge the offer by its total annual cost.

• Contracts signed without clear consent: Doorstep or phone contracts are sometimes signed or switched without your clear consent, and suppliers can change prices with notice. Never agree on the spot. You can withdraw within 14 days, as explained in the article on salespeople who say they are your electricity company.

Estimate your annual electricity cost under different offers

Work it out

What you enter

• Yearly use in peak hours (punta) (kWh): Your last 12 months of bills or your distributor's online consumption data; peak is weekdays 10:00-14:00 and 18:00-22:00.
• Yearly use in flat hours (llano) (kWh): Your yearly consumption by period; flat is weekdays 8:00-10:00, 14:00-18:00 and 22:00-24:00.
• Yearly use in off-peak hours (valle) (kWh): Your yearly consumption by period; off-peak is weekdays 0:00-8:00 plus all weekends and national holidays.
• Contracted power (kW): Your current bill or contract, under contracted power (potencia contratada).
• Offer price per kWh in peak hours (EUR/kWh): The offer's price table, before taxes.
• Offer price per kWh in flat hours (EUR/kWh): The offer's price table, before taxes. If the offer has one flat price, enter it in all three energy prices.
• Offer power price per kW and day, peak hours (EUR/kW/day): The offer's price table, under término de potencia, before taxes.
• Monthly meter rental (EUR): Your bill's equipment rental line or the offer's conditions; enter 0 if there is none.

Figures used

• Days in a year: 365 days
• Electricity tax rate (impuesto eléctrico): 5.11 % (as of 2025)
• IVA on mainland and Balearic Islands: 21 % (as of 2025; check the current figure before you rely on it)

Worked example (with Yearly use in peak hours (punta) 900 kWh, Yearly use in flat hours (llano) 1,100 kWh, Yearly use in off-peak hours (valle) 1,500 kWh, Contracted power 4.6 kW, Offer price per kWh in peak hours 0.2 EUR/kWh, Offer price per kWh in flat hours 0.15 EUR/kWh, Offer price per kWh in off-peak hours 0.1 EUR/kWh, Offer power price per kW and day, peak hours 0.07 EUR/kW/day, Offer power price per kW and day, off-peak hours 0.03 EUR/kW/day, Monthly meter rental 0.8 EUR)

When the sum misleads

• Run the sum once per offer and compare the yearly totals, not the headline price per kWh.
• In the Canary Islands, Ceuta and Melilla, replace the IVA rate with the local tax rate (IGIC or IPSI) for your area.
• The electricity tax has minimum amounts per kWh or kW, so a very low bill may come out slightly higher than this sum.
• Offers with a fixed discount, free hours or extra service fees need those added or subtracted by hand.

Check the current tax rates for your region with the Agencia Tributaria, and use the prices written in each offer, which should already include the regulated charges.

Frequently asked questions

What details do I need to enter in the official comparator?

You need your postcode, your tariff access type, your contracted power and your yearly consumption.

Is the yearly cost shown in the comparator guaranteed?

No, the yearly cost is only an estimate based on the data you entered. The comparator also lists only offers that suppliers have registered. The supplier's contract terms are what count, so read them before you sign.

Can a 'free' energy offer still cost me more?

Yes, a 'free' energy offer can cost more if the supplier raises the power charge to make up for it. Compare the full annual cost, not the energy price alone. Indexed prices can also look cheap but move with the market.

Which details must the contract show about price changes?

The contract must state the conditions for any price revision, so look for them before signing. It must also show the CUPS and your contracted power. Check that these match your current bill.