Bosses of the UK's energy network companies have defended the length of time it took to restore power to homes in the face of "severe, national" storms over Christmas.
Thousands of homes in Sussex were left without electricity over the festive period, with some experiencing three power cuts in a week.
Basil Scarsella, chief executive of UK Power Networks, told MPs that the combination of the storms' severity and their national reach meant that "tried and tested" plans struggled to cope.
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He said: "We have a tried and tested system that comes into play when there's an emergency such as that. You're correct, we knew that there were storms. We have a methodology that estimates the damage expected on the network based on the wind speeds.
"But the wind speed and the weather forecast escalated significantly on the Sunday and went from 40-50mph winds on the Friday to 50-60mph for our area, and escalated to 70-80mph on the Sunday.
"But notwithstanding that, we managed on the Monday when it hit to have all our workforce pretty much on deck and our estimation of the damage was pretty accurate.
"What we did not estimate accurately was the duration of strong winds which resulted in significantly more severe damage.
"The other issue was that this was a national storm and it lasted over two or three days. There is a well-tested mutual aid system which enables any of us to call on our colleagues to send additional resources.
"But because of the severity of the storm and the national nature of the storm we were not able to provide additional resources to other networks or indeed receive additional resources.
"So there's a combination of the severity of the storm and the national nature of the storm."
More than 150,000 homes were cut off after strong winds, torrential rain and flooding caused damage to power networks, with many were left without electricity for up to five days.
Energy committee chairman Tim Yeo lambasted the power bosses for failing to show "any expression of real concern for your customers".
"I have to say after 45 minutes the tone of this discussion and its contents has been utter complacency from all of you.
"The trade body can't provide the most basic information on a totally predictable question.
"You have lacked any expression of real concern for your customers. It's absolutely typical of a monopoly, particularly monopolies whose charges are not very visible to the customers who have to pay them."
Mr Yeo warned the witnesses to "step your act up" if they wanted to "impress" the committee.
Mark Mathieson, managing director of SSE's electricity networks, said: "It was just the impact of the event. It was a massive event. Certainly we haven't seen damage like this in the south back from the early 90s and even back to the great storm of 1987.
"I think the one thing I would say, and I've been in this industry for 25 years, we as an industry clean these events up much quicker than we used to. But we also recognise the impact that has on customers.
"We are sorry and I did go out to communicate with customers that we were sorry that they were off.
"To get to the area and fix faults, in some circumstances when you've got damage like that, when you've got devastation like that, it unfortunately takes time. But that's where we go the extra mile. I know it's not the same as being at home with the power on but we were offering accommodation and hot meals."
Asked if the network companies could work with other agencies to improve response times, Mr Mathieson said: "We're actually going out to every regional forum to see if lessons can be learnt. This industry has to learn lessons.
"I know it seems a long time when customers are off but you go back 20 years and that could quite easily have been two weeks. The only way we are going to improve is to learn lessons and we will learn the lessons and we will work with partners and build working relationships for the next time."