The news is the latest in a run of bad publicity for the industry and its regulatory bodies.
It follows a January study by the EU which showed that electricity costs in Spain have risen by 46 percent since 2012, the second-biggest increase in Europe.
Another study in February from the Factua-Consumidores en Acción group revealed that electricity in Spain was 48 percent more expensive than in the cheapest European countries.
Last year, news that the government planned to "tax the sun" by forcing owners of solar panels to connect them to the national grid and pay VAT on the electricity they generate was widely mocked in the international press.
The new "smart meter" technology behind the current headlines will eliminate the need for electricity company operators to visit properties to read meters and determine the amount of energy consumed.
Ten percent of homes already have smart meters and they are scheduled to be fitted to every residence in Spain by 2018.
A spokesperson for the CNMC said, "The benefits are for the companies, because when they are installed and connected they will save by eliminating reading costs."
Companies will also be able to invoice customers monthly instead of bi-monthly or quarterly.
Jorge Morales, member of the Platform for a New Energy Model, told Spanish daily El Diario: "The main problem is that there's no advantage for the consumer."
"They could provide the user with a lot of information, but they don't," he added.
"They could inform consumers in the case of supply cuts, for example; they could be configured to improve consumption. That's why we've asked that the installation plan be put on hold until the end user can get information from the meter."
The legislation in Spain does not permit the fitting of meters capable of connecting to tablets or smartphones.
"I'd buy one of those," said Morales. "It would help me to know and manage my consumption much better."
"But they won't let me," he said.
He added: "When you have information, when you know what you're spending and when you're spending it, you can control it. You could know immediately how much your consumption goes up when you plug in the washing machine and choose the best moment to use it."
The CNMC noted that "there is no cost to users for the replacement of the meters as part of the plan."
But the rent charged to users for the new meters will almost double, from €0.47 to €0.81 per month.
These rates are currently under review after a supreme court ruled them to be "badly calculated" but the CNMC has yet to release new figures, despite the deadline of December 15th 2013 having expired.