British Gas customers have been struggling to submit their meter readings ahead of the price cap rise.
This comes as reports of energy suppliers including EDF, E.ON and SSE websites have crashed, according to consumer champion Which?.
According to Down Detector, 350 customers are experiencing problems logging into their E.ON accounts.
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Martin Lewis raised a concern on Twitter yesterday asking his followers if they were having problems submitting, to which over two thousands people commented, sharing the issues they are having with British Gas.
British Gas have replied to some saying that they are aware of the issue that has been occurring since February.
Some are receiving a message when trying to submit their meter readings on British Gas that say: "We're really sorry if you can't access your up to date energy usage - there are some technical issues displaying usage since 16/02/2022. We're trying to resolve as quickly as possible. Thank you for your patience."
British Gas has been contacted for comment.
And today, hundreds reported that they weer unable to log their readings to EDF.
EDF responded on Twitter: "Our website and app are experiencing extremely high traffic. Our speedy tech teams are currently working on this in the background."
This comes as March 31 marks 'meter reading day' as customers are being urged to submit their meter readings before April 1 to "draw a line in the sand" ahead of the massive price hike that will see bills rise by 54 per cent.
Already Octopus Energy have confirmed that their phone lines are dealing will a lot of heavy traffic but they say that their variable tariff doesn't change until Saturday midnight.
Which? are encouraging people who are having difficulty submit their readings online to phone suppliers and take a photo.
They tweeted: "IMPORTANT FOR #MeterReadingDay Hearing lots of reports from people struggling to submit meter readings because their energy firm's website is down. If you can't submit - take a photo of your meter reading so you can prove when it was taken.
"Some energy companies also have automated phone lines you can use to submit meter readings, people can also try calling these numbers or emailing if they can't submit readings online."
Martin Lewis has since tweeted saying that companies 'should have been prepared and adds: "If you can't get to do a meter reading today, do it tomorrow, or Sunday, or Monday. The nearer to today you do it the less chance of mis-estimates, so don't panic about missing it (either through your own or the firm's issue) just get it in as soon as you can."
Have you had issues inputting your meter readings? Let us know in the comments.