In the wholesale market, where producers sell electricity to traders and large consumers, the average price at which electricity is sold this Monday in Portugal is around four times higher than that recorded in neighbouring Spain, according to a report by ECO.

The average price per megawatt-hour in Portugal, this Monday, is 43.94 euros, with the most expensive megawatt-hour reaching 62.73 euros and the cheapest being 30.36 euros. In contrast, on the other side of the border, the megawatt-hour averaged 10.89 euros, and the maximum price was slightly higher than the minimum price in Portugal: it was 35 euros. The lowest recorded in Spain was minus 4 euros per megawatt-hour.

Prices in the two countries are usually neck and neck, as the Iberian market is completely integrated. However, since the blackout last Monday, for security reasons, the operator of the national transmission networks, REN, decided to break the connection with Spain, stopping importing electricity produced in that country. A situation that REN expects to maintain until this Tuesday, according to the latest information communicated on the company's website.

The day after the blackout, electricity market prices were in line in the Iberian market – at 5.79 euros per megawatt-hour – but, from then on, some differences were noted, not always in Spain's favour. For example, on 30 April, the neighbouring country recorded an average price of 31.83 euros, while Portugal recorded an average price of 20.54 euros.

On 1 May, the trend reversed, with Portugal paying an average of 18.85 euros and Spain at 13.29 euros. On 2 May, the difference between the two countries dictated that Portugal would surpass Spain by 3 euros per megawatt-hour. On the 3rd, the difference was smaller, just over 1 euro. However, on the 4th, the gap reached more than 9 euros and finally, this Monday, Portugal scored four times as much.

Wholesale price differences do not have a direct impact on most invoices, which are contracted at a fixed price for 12 months. However, this can be seen on the invoice for indexed tariffs – which, however, had several days of negative prices in April, which may help to dilute the negative effects of the blackout.