National Grid is responsible for ensuring supply and demand are balanced in Britain's energy systems.
"Unusually low wind output coinciding with a number of generator outages means the cushion of spare capacity we operate the system with has been reduced," National Grid Electricity System Operator (ESO) said on Twitter.
The grid has a number of tools to help balance supply and demand and paid power producers such as nuclear generator EDF to reduce output over the summer when demand was weak.
"Margins remain adequate for today and we're continuing to monitor the situation for the coming days," a spokesman for National Grid said via email.
"We were in touch with providers in the market... to make sure there was as much generation available as possible to operate the system securely today," the spokesman said.
National Grid said it had not needed to issue formal system notices to the market which call on generators to ramp up or reduce electricity production.
British wholesale electricity prices for day-ahead delivery rose around 20% on Thursday to 60 pounds per megawatt hour.
Gas power plants were supplying around 55% of the country's electricity on Thursday morning, with nuclear at 16% and wind at 15%, National Grid data showed.
(Reporting by Susanna Twidale; Editing by Edmund Blair and Emelia Sithole-Matarise)
By Susanna Twidale