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Do you know your cheapest time-of-use tariff hours?

Clock under lightening

About 3.9m UK households are on energy tariffs, which mean they get cheaper electricity at certain times. So you’d think it’s important to know exactly what those hours are to make sure you save as much as you can…

…but it’s not always an easy task.

Take Which? member Sue Hufton. The 58-year-old from Leicestershire thought her bills seemed high so decided to check the hours of her Economy 7 tariff.

She assumed a quick call to supplier Scottish Power would give her the answer.

But after numerous phone calls – and 39 days of watching her meter – she was still none the wiser.

She is one of a number of time-of-use tariff customers who have contacted Which? for advice on checking their tariff hours or meter clock.

The cheapest hours

Mrs Hufton said Scottish Power initially told her to contact her distribution network operator, which could not help. They then told her to call the meter manufacturer, which also could not help. Finally she said Scottish Power advised her to watch her meter to see when it changed over. She told us:

‘Over a period of 39 days, believe it or not, I kept a close eye on the meter around the time I thought that it may change over. I lost the will to live in the end.’

Mrs Hufton fears she could have paid more than she needed to by not knowing her cheaper hours.

Economy 7 generally offers seven hours of cheaper electricity overnight. But the exact hours vary between supplier, region and season.

Scottish Power apologises

After Which? intervened to help Mrs Hufton, Scottish Power said her off-peak hours were midnight to 7am GMT and 1am to 8am BST. A spokesman said: ‘We have contacted Ms Hufton and apologised.’

It has also sent Mrs Hufton some flowers by way of apology.

Ofgem says customers who can’t find their meter clock or suspect it is faulty should contact their supplier. But be warned – some charge fees if they are called out but then find the clock is correct.

Are you on a time-of-use tariff? And do you know your cheaper hours? Have you ever had trouble finding them out?


We have cheaper off-peak electricity so that heavy users can benefit from excess generating capacity overnight, when demand is lower. If meter clocks are set incorrectly, users may be using storage heaters and other high demand appliances when demand is high, meaning that more generating capacity is needed. All forms of electricity have an environmental impact and it is irresponsible for the suppliers not to keep meter clocks set correctly.

This is yet another example of incompetence by energy companies, who should be fined.


So long as the fines come off the profits and are not put on the tariffs I agree with you. There is absolutely no excuse for two-part meters not to be as accurate on time as they are supposed to be on Kwh used and the Regulator should require all supply companies to contract with their meter-reading agents to carry out a reliable time check every time they physically inspect a meter. Accurate time time recording might just persuade me that smart meters are a good idea.


John – I agree that fines should be paid for out of profits and not passed on to customers. It should be a requirement for fines to be reported in the Annual Report, hopefully with an indication of what action is to be taken to avoid future penalties.


I Googled “Scottish Power Economy 7” and it immedisately produced this very comprehensive document that gives nationwide tariffs, explains hours for white meters, describes how weather-adjusted heating is operated and so on.


That’s helpful Malcolm, and good of ScottishPower to provide this information. Some friends of ours [whom I mentioned in another Conversation about out-of-synch meters] had enormous difficulty getting their electricity supplier to give the hours when the night and day rates would operate in their apartment. All suppliers should be able to look up a meter number and quote the switch-over times [it was complicated in their case because they could not get access to the meter which was in a locked room in the block].

I note from the ScottishPower leaflet that ‘Night’ is formally defined as any period of 8.5 hours at ScottishPower’s discretion between 2200 and 0830 GMT, but in practice should be one of the following:
(a) 2300 to 0730 GMT (i.e. 0000 to 0830 BST in summer), OR
(b) 2345 to 0815 Local Time (i.e. same clock time all year), OR
(c) 0000 to 0830 Local Time at the choice of ScottishPower.
and that ‘Day’ means at all other times.

They’ve left themselves some wriggle-room so it’s still a good idea for Economy 7 consumers to ascertain the exact timings as well as check that the time-clock on their meter is both accurate and in synchrony with current time.


I was on Economy 7 for donkeys years, but as I’m slowly trying to reduce my usage, it got to the point that the standing charge on Economy 7 meant I was better off switching to a standard tariff.

If nothing I think the neighbours will probably enjoy the fact that I no longer run the washing during the night.

Alex M says:
21 April 2014

It’s not just the on/off times, are you getting the full 7 hours?
In addition to finding it difficult to obtain the on/off times for Economy 7, I also discovered that I wasn’t getting the full 7 hours lower price period, more below. Switching on my meter is by radio tele-switch. My supplier, OVO, told me to contact the local network management company who, when I eventually found out who it was, told me to talk to OVO. After several attempts I was given times but, unlike above I was told that the switching times were the same regardless of whether it was GMT or BST. I concluded that I didn’t really trust the information provided. Regarding the 7 hour low-price period and on account of the unwillingness of my provider to be clear about the on/off times, I wondered if they were less than honest about the full 7 hours. So, I did the following; I turned off all electrical power except for a one kilowatt heater which was switch on at 11pm and off at 8pm, taking meter reading immediately before and after this action, So, my nominal one kilowatt heater was on for 9 hours in which case my actual total consumption was a little under 9kWh. In this case, by starting at 11pm and finishing at 8am, I reckoned that 7 of the hours should be on economy 7, or 7/9ths of the total. Likewise the power consumption on economy 7 should be 7/9ths of the total. I divided the kWh on the low indicator by total consumption over the 9 hours to find that my Economy 7 was only active for under 6.5 hours. I repeated the experiment a few days later and recorded almost the same result. Now either the on/off times I was given (12 to 7) are very wrong or the power companies are selling us short!

David James says:
23 April 2014

Hi Brilliant articles in Which? last month and in the May issue on meters. I left a message for the team this morning with Emma and having spoken to Scottish Power a few minutes ago are updating you on progress. Like Mrs Hutton in your May page 5 article have been given the run around by Scottish Power (SP) – but unlike her I have made it known that a bunch of flowers will not help.
Thanks to your earlier article I checked the time setting on my meter and found it was running fast. I contacted SP and was given the run around – even given an incorrect start/finish time of economy 7. After a lot of persistence SP offered to change the meter but their contractor failed to show.
After more dialogue with SP an engineer called this morning and changed it, confirming that the old meter was running 45 minutes fast.
This is critical to the way we use cheap rate power – we have the washing machine and dishwasher on delay start/timeswitches set to run during the night but only use the tumble dryer when someone is around (fire risk). During winter months I usually load it at around 6.30am and run it for about an hour believing that this was within the “cheap” rate. But as the meter was 45 minutes fast and the “cheap” rate was supposed to be from 00.30 to 07.30 GMT the “normal” rate was actually commencing at 06.15 therefore the majority of the drying time was at “normal” rate rather than “cheap rate”.
I have spoken to a very helpful person at SP this morning who has taken all the details and promised to escalate the problem and call back later to let me know progress.
So, thanks for the original article pointing out the problem with meters – I will let you know progress.
David James,