Best Buy UK has incurred operating losses of £29m for the six months to September 30, 2010, according to Carphone Warehouse, which launched the format with US giant Best Buy in April.
Carphone Warehouse said it will continue to invest in Best Buy UK with "greater marketing activity that initially planned", with operating losses expected to be between £50m and £55m for the full year.
Carphone Warehouse Group ceo Roger Taylor said: "We have delivered a strong first half with good performances across all our businesses, and we are raising our guidance for the full year."
Commenting on Best Buy UK's result, he added: "Customer response to our first five Best Buy branded 'big box' stores has been overwhelmingly positive, with the sixth store opening in Derby today. With yesterday's launch of its transactional website, Best Buy gains national reach and is able to compete as a truly multi-channel retailer."
Best Buy Europe, which includes Carphone Warehouse in the UK and Phone House, generated an 81% increase in EBIT year-on-year, from £32m to £58m. Of this, £43m was contributed by Best Buy's mobile phone retailing operations in the US.
Best Buy UK's £29m EBIT loss reflected further investment in infrastructure and IT, together with launch costs for the first stores and online platform, said Carphone Warehouse.
Best Buy UK launched its transactional website yesterday, heating up competition with rivals Currys, Comet and Argos.
The site will offer all products that are available in store at the same price, as well as an expanded selection of products, which will also be available to purchase instore via online kiosks.
The retailer is offering free delivery to UK customers, and will also offer a Reserve & Collect facility where customers can reserve items from their nearest store, receiving notification of when their purchases are ready for collection within an hour.
Best Buy UK managing director for online deVere Forster said: "The launch of our e-commerce site on bestbuy.co.uk marks a key milestone for the business and helps to make buying technology simple, inspiring and tailored to each of our customers. We are very excited that customers from across the UK will now be able to experience the Best Buy brand for the first time."