Electricity billed by the hour from today for 'smart-meter' households

Effectively, this involves 24 tariffs throughout the day and, based upon bi-monthly bills covering a typical 60 days, a total of 1,440 different prices, according to utility boards.

Only customers whose electricity is supplied by the so-called 'regulated market', rather than those who have shopped around for different providers, will be affected since independent utility firms offer their own individual formulae for billing.

Presently, a total of 14 million people in Spain are 'regulated market' electricity consumers and will now be billed by the hour.

The difference between peak rates and the cheapest rate of the day can be as much as 31%, according to figures published by the national grid.

Information in real-time is sent to suppliers via the digital or 'smart' meters which are gradually being rolled out across Spain, with updates every 20 seconds.

Hourly billing is only possible for those with 'smart' meters already fitted – expected to be 16 million households by the end of this year, or 57% of the total, although only about half of these are on 'regulated market' electricity.

By the end of 2018, the government wants all homes and businesses with power supplies of up to 15kW to be on smart meters.

Fitting these does not attract a cost to the consumer, meaning if anyone tries to charge for doing so, alarm bells should ring instantly.

'Renting' the meter costs 81 cents a month, which is 40% higher than the price of renting an analogue meter.

Customers are permitted to buy their own meter if they wish, but this is an expensive option of limited investment value and will not speed up the process, since the electricity board still needs to arrange to fit it.

Also, the geographical area in question needs to have the necessary infrastructure to allow digital transmitting of data, which may not be the case in certain remote, rural parts of Spain.

Consumer societies are not sure that hourly charging will change customers' power use habits, or really save them any money since around 60% of each electricity bill is made up of taxes and standing charges, with only 40% relating to actual consumption.

But a consumer consultancy's report gives some clues on how to keep costs down.

The most expensive time of day for using electricity is between 21.00hrs and 22.00hrs on any day of the week, whilst the cheapest is between 02.00hrs and 03.00hrs.

Between 15.00hrs and 17.00hrs is also one of the most economical time slots.

Weekends are an average of 7% cheaper than weekdays, and Sunday is the most economical day, with a typical saving of 9%.

The best time of the week to carry out housework involving electricity is on Sundays during 'siesta time', or between 15.00hrs and 18.00hrs.

Where possible, avoid or reduce electricity use on Mondays between 20.00hrs and 22.00hrs.

However, even these time slots may be subject to change – a report shows that on September 11, the most expensive hour of the day was between 06.00hrs and 07.00hrs, and the cheapest between 23.00hrs and midnight.