Bosses said Covid-19 costs also increased but recent high energy prices helped the group hit pre-tax profits of £907m in six months.
British Gas owner Centrica swung back into profit this year as the company enjoyed the benefits of a spike in global energy prices and completed the sale of its North American business, Direct Energy, for 3.6 billion dollars (£2.3 billion).
The pre-tax profit of £907 million in the first six months of the year, compared to a £462 million pre-tax loss in the same period last year, came despite bosses revealing British Gas customer numbers continue to fall and the company saw an increase in costs associated with the Covid-19 pandemic.
In its British Gas division, which has struggled with fleeing customers as smaller rivals eat into the market, 114,000 gas and electricity customers switched supplier – with the company saying many chose to switch following a recent increase in the energy price cap.
Around 144,000 customers also left its services business – down 4% on the same period a year ago.
The Covid-19 crisis and industrial action taken by staff also cost the business £80 million in the first six months of the year – an increase of £58 million in the same period a year ago.
But British Gas energy profits increased 121% to £172 million due to the cold weather, an increase in business usage as the economy opened up and a reduction in Covid-related costs for the division, versus the entire Centrica group.
The rising costs of energy also helped Centrica’s commodity division as it could sell the units of energy produced at a higher price due to demand increasing from businesses as the global economy opened up again.
Bosses added they still intend to exit oil and gas production and have made progress towards pursuing alternative sale options of their assets.
But they said they are reconsidering whether to sell a 20% stake in nuclear power stations, having first announced plans to leave the division in 2018.
On Thursday, the company said: “We have been reconsidering whether Nuclear can play a role for Centrica in the future… Our focus remains on the customer, and as we look to help our customers reduce their carbon emissions, our nuclear stake provides us with an important source of zero-carbon electricity. Therefore, we may decide to retain our 20% interest.”
Earlier this month, a long-running dispute at British Gas ended after workers accepted an improved pay deal.
Around 7,000 British Gas engineers staged 44 days of strike action stretching over several months.
The GMB union declared an end to the so-called “fire and rehire” dispute after its members backed an agreement by three to one.