UK's 3 bln pound green home scheme not value for money -watchdog

* Schemes cost 94 pounds for each tone of CO2 saved

* Green deal cost tax payers 240 mln pounds (Updates with details on cost savings and government comment)

LONDON, April 14 (Reuters) - A British government scheme costing energy firms 3 billion pounds to help people cut their bills and greenhouse gas emissions through measures such as subsidised loft insulation has not been value for money, a parliament watchdog said.

The report, by the National Audit Office (NAO), said "neither we nor the Department (of Energy and Climate Change) can determine the impact of the schemes on fuel poverty", while the average cost of cutting just one tonne of carbon dioxide (CO2) was around 94 pounds, almost three times the cost of earlier schemes.

The country has some of the most energy inefficient homes in Europe and the measures had been expected to help the country meet its greenhouse gas reduction targets.

The government is also under pressure to curb rising energy bills with 2.3 million of Britain's 27 million households deemed fuel poor, meaning the cost of heating their homes leaves them with income below the poverty line.

Since 2013 power suppliers are required to install energy efficiency measures such as loft insulation in some of their most vulnerable customers' homes under the government's Energy Company Obligation (ECO).

Several companies, including Centrica (LSE: CNA.L - news) and RWE (LSE: 0FUZ.L - news) 's npower have long criticised ECO as too expensive.

The NAO said ECO had cost energy suppliers 3 billion pounds ($4.3 billion) from 2013 to 2015 and improved the energy efficiency of 1.4 million homes. By the time the scheme ends on 31 March 2017 it is expected to save 34 million tonnes of CO2.

The NAO said the scheme had generated a potential saving for the households who benefited of around 6.2 billion pounds.

Under a separate initiative, The Green Deal, the government offered homeowners loans to pay for green products such as energy-efficient boilers, but uptake was slow and the project was scrapped last year.

The NAO report said the scheme cost taxpayers 240 million pounds with just 14,000 homes benefiting from improvements.

"This government is clear about the need to have firm financial controls in place to protect consumers, which is why we took action last July... stopping funding to the Green Deal Finance Company and setting up an independent review of the energy efficiency sector," a spokeswoman for the Department of Energy and Climate Change said.

"We are now designing a new scheme that will help make even more homes warmer and bring people's bills down.

($1 = 0.7034 pounds) (Reporting by Susanna Twidale; editing by Susan Thomas and David Evans)