SCOTTISH Gas owner Centrica has warned its profits for this year will be hit by a warmer than expected autumn.

The temperate weather and outages at two of its nuclear power stations were given as the main reasons for the company trimming its earnings per share forecast to between 19p and 20p, down from the 21p to 22p it had earlier predicted.

For consumers, the milder weather in recent months coupled with greater energy efficiency measures is expected to knock £100 off annual dual fuel bills.

Residential account numbers were said to have fallen by 50,000 since the end of June to around 15 million, but Centrica said it has seen a rise in customer numbers in recent weeks as a result of a new energy tariff launched in partnership with supermarket Sainsbury's.

Around 1.1 million smart meters have now been installed in the homes of UK customers and Centrica expects to have sold 150,000 smart thermostats, which can be operated remotely and through mobile device apps, by the end of this year.

Centrica also said the shut down of boilers to allow inspections to be carried out at the Heysham One and Hartlepool nuclear power stations had affected profits projections for this year.

Chief financial officer Jeff Bell said: "We've continued to see in the autumn the warm weather that we saw earlier in the year here in the UK, and that's led to lower consumption for our customers. At the same time, two of our nuclear power stations have had issues and those are only now coming back online.

"So for both of those external reasons, primarily they are the drivers of our lower earnings forecast."

The company also indicated its oil and gas exploration and production business will see a tumble in profits during 2015 if oil prices remain at current low levels. It also highlighted that certain tax breaks related to small fields would not be available next year and that would also hit earnings.

Spending on upstream projects next year is likely to come in at around £900m, from around £1bn across 2014. A further cut in exploration and production spending may also be made in 2016.

Total gas and liquids production, from North Sea and international operations, in the current calendar year are to be around 80 million barrels of oil equivalent, which is slightly down on previous estimates.

It said that the change is mainly a result of gas export pipeline constraints, which had affected its Greater Markham Area, which is run from the Netherlands.

Centrica, which paid £1.3 billion for Venture Production in 2009 and employs around 400 staff in its Aberdeen centre, said that in spite of the uncertainty over oil prices it still anticipates modest earnings growth across the group next year helped by its operations in North America and Ireland.

Mr Bell said: "There is no question that lower gas and oil prices will lower the profitability of our Centrica Energy business, both in power and gas and we would expect earnings next year to definitely be lower than they are this year.

"However, we continue to invest material amounts of money this year, about a billion pounds in sourcing new gas supply for our customers in the UK and we will be bringing on-stream in the next year or so two significant fields - Cygnus and Valemon - to help support our customers."

The Valemon field is on course to produce its first gas early next year with Cygnus expected towards the end of 2015. Shares in Centrica closed down 4.7p, or 1.6 per cent, at 293.9p.