Daytime broadband usage has jumped from between 35% and 60% compared to the average day in the UK, as mobile phone companies see a drop in data use.
The peak reached 7.5 terabits per second, only around half the average evening peak.
This is still below the highest ever peak – 17.5 terabits per second – which it has seen as a result of videogame updates and football streaming in the past, the telecoms giant said.
Virgin Media reported a similar jump in broadband usage, with traffic up by as much as 50% during daytime hours, but also below regular peak evening levels.
Despite being confident that its broadband network is within manageable limits, BT said it is not complacent.
‘The Covid-19 outbreak is causing changes to the way our networks are being used,’ said Howard Watson, chief technology and information officer at BT.
‘We’re monitoring those changes carefully to make sure we can respond rapidly if needed.
‘However the UK’s communications infrastructure is well within its capacity limits, and has significant headroom for growth in demand.’
Mobile data traffic has fallen by 5%, BT said, as more people connect their smartphones to Wi-Fi.
Data usage is peaking at around 5pm, when Boris Johnson holds a daily briefing on the situation.
Meanwhile, Virgin Media has noticed a large growth in demand on its landline network, with voice calls up 80% week on week during its busiest period in the morning.
A 10am peak sees just under three million calls per hour, and people are spending nearly twice as much time on their landline phones in the early evening, with phone call minutes up by as much as 94%.
Despite assurances, both Netflix and YouTube have decided to limit video-stream quality in an effort to ease pressure on internet providers during the coronavirus outbreak.