Competition is "fierce" among the UK's energy suppliers - on a range of factors going beyond price, a new report states.
Research from market regulator Ofgem states that consumers are increasingly paying attention to environmental credentials - and providers are having to adapt their offerings for vulnerable low-income groups.
These factors are driving competition, the energy watchdog says.
And, as around ten per cent of consumers switch providers as a result of dissatisfaction with customer service levels, suppliers are making sure they improve on these parameters - and complaint levels are falling as a result, Ofgem says.
High switching rates mean the market is working well and that poor-performing companies are being "punished", according to Ofgem chief executive Alistair Buchanen.
"Suppliers are responding by cutting prices, improving service and developing new energy products to attract and retain customers. But a large number of customers are still missing out on savings of up to £100 and better customer service by not shopping around," he said.
"Customers have a choice and can switch away from suppliers who offer high prices or poor service."
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