Aug 16 (Reuters) - Europe is facing a sharp rise in power bills driven by sky-rocketing gas prices, as war in Ukraine and European sanctions on Russia heighten concerns over the security of gas supplies.

Here are some of the policies Britain and European Union member states have announced to help shield consumers (in alphabetical order):

BRITAIN

Britain has a price cap on the most widely used household energy contracts. The cap from October will be announced on Aug. 26.

Forecasting group Cornwall Insight estimates that average British annual bills for gas and electricity will jump to 3,582 pounds ($4,311) in October and 4,266 pounds in January. Earlier this year, the price cap was 1,277 pounds.

The government is facing growing calls to provide more support to households struggling with energy bills, but Prime Minister Boris Johnson has said he will leave major fiscal decisions to the new prime minister.

The Conservative Party leadership contest between Foreign Secretary Liz Truss and former finance minister Rishi Sunak runs until Sept. 5.

Truss has said she would apply a temporary moratorium on environmental and social levies added to consumers' electricity bills.

Sunak has said he is in no doubt more support will be needed to help households through the winter, and he would act as soon as it is confirmed how much bills would be increasing by.

In May the government set out a 15 billion pound support package to help households. Every household will receive a 400 pound credit to their energy bills from October.

More than 8 million low-income households receiving state benefits are also being given a further one-off 650 pound payment, with additional help for pensioners and disabled people.

BULGARIA

Bulgaria has introduced a discount of 0.25 levs per litre of petrol, diesel and liquefied petroleum gas and methane from July until the end of the year for households and scrapped excise duties on natural gas, electricity and methane.

The country, a net electricity exporter, has also kept regulated prices for electricity for households at bay, allowing only an average 3.4% annual increase as of July.

DENMARK

In June, Danish lawmakers agreed a cash handout to the elderly and other measures totalling 3.1 billion Danish crowns ($439 million) to cushion the impact of soaring inflation and high energy prices, including a cut to a power price levy.

Danish lawmakers had previously agreed on subsidies worth 2 billion Danish crowns ($288 million) to be paid to some 419,000 households hard hit by rising energy bills.

EUROPEAN COMMISION

European Union countries are largely responsible for national energy policies, and EU rules allow them to take emergency measures to protect consumers from higher costs.

The EU in July asked its member states to reduce gas demand voluntarily by 15% this winter, with mandatory cuts possible.

The bloc also aims to refill storage to 80% of capacity by Nov. 1.

FRANCE

France has committed to capping an increase in regulated electricity costs at 4%. To help do this the government has ordered utility EDF, which is 80% state owned, to sell more cheap nuclear power to rivals.

New measures announced since the Ukraine crisis - such as helping companies with the cost of higher gas and power bills - bring the total cost of the government package to 25 billion-26 billion euros ($27 billion), Finance Minister Bruno Le Maire said.

French energy regulator CRE said last month it was proposing a 3.89% increase in regulated electricity sales tariffs (TRVE). The government has the ability to oppose the regulator's proposed rate hike and set new tariffs at a lower level or reject them outright.

GERMANY

German workers and families will receive extra cash, cheaper petrol and cut-price public transport tickets.

Workers who pay income tax will receive a one-off energy price allowance of 300 euros. Families will receive a one-time bonus of 100 euros per child, which doubles for those on low incomes.

Over the next few years, some 12 billion-13 billion euros per year will be allocated to subsidise renovations to old buildings.

However, German households will have to pay almost 500 euros ($510) more a year for gas after a levy was set to help utilities cover the cost of replacing Russian supplies.

The levy, introduced to help Uniper and other importers cope with soaring prices, will be imposed from Oct. 1 to April 2024.

GREECE

Greece has spent about 7 billion euros on power subsidies and other measures since September.

Subsidies, which will be incorporated into power bills, will come in at about 1.136 billion euros in August and absorb up to 90% of the rise in monthly power bills for households and 80% of the rise for small and medium-sized firms.

Greece has imposed a cap on payments to power producers to reflect their real production costs, effectively scrapping a surcharge on electricity bills, with proceeds earmarked to help it finance power subsidies.

HUNGARY

Hungary has capped retail fuel prices at 480 forints ($1.23) per litre since November, well below current market prices. The measure led to such an increase in demand that the government was forced to curb eligibility for the scheme.

Sharp rises in gas and electricity prices have also forced Hungary's government to curtail a years-long cap on retail utility bills, setting the limit at national average consumption levels, with market prices applying above that.

Hungary has also imposed an export ban on fuels and recently loosened logging regulations to meet increased demand for solid fuels such as firewood.

ITALY

The country in early August approved an around 17 billion euro aid package to help shield firms and families from surging energy costs and rising consumer prices.

That comes on top of some 35 billion euros budgeted since January to soften the impact of sky-high electricity, gas and petrol costs.

Under the package, Rome extended to the fourth quarter existing measures aimed at cutting electricity and gas bills for low-income families as well as reducing so-called "system-cost" levies.

A cut in excise duties on fuel at the pump scheduled to expire on Aug. 21 is set to be extended to Sept. 20.

Rome is also considering preventing energy companies from making unilateral changes to electricity and gas supply contracts until April 2023, according to draft measures approved by the government in early August.

NETHERLANDS

The Netherlands has cut energy taxes for its 8 million households.

NORWAY

Norway has been subsidising household electricity bills since December and currently covers 80% of the portion of power bills above a certain rate. This is due to increase to 90% from September, with the scheme to remain in place until at least March 2023.

POLAND

Poland has announced tax cuts on energy, petrol and basic food items, as well as cash handouts for households. It has also extended regulated gas prices for households and institutions like schools and hospitals until 2027.

The government in July agreed a one-off payment of 3,000 zlotys ($648) to households to help cover the rising cost of coal. Prime Minister Mateusz Morawiecki has said the total cost of curbing energy prices in Poland will reach around 50 billion zlotys.

ROMANIA

Romania's coalition government has implemented a scheme capping gas and electricity bills for households and other users up to certain monthly consumption levels, and compensating energy suppliers for the difference. The scheme is due to be in place until March 2023.

Romanian Prime Minister Nicolae Ciuca estimated in February the support scheme will cost around 14.5 billion lei ($3.27 billion), but analysts now expect it to exceed 10 billion euros.

The leftist Social Democrats, parliament's biggest party and a part of the governing coalition, support replacing the scheme with regulated prices.

SPAIN

Spain has started to temporarily subsidise fossil fuel plants' power costs in a bid to bring down high prices in the short term. The system is due to be in place until May 31, 2023.

It has also cut taxes to reduce consumer bills, and announced 16 billion euros in direct aid and soft loans to help companies and households weather energy prices.

SWEDEN

Sweden has set aside 6 billion Swedish crowns ($605 million) to compensate households worst hit by the surge in electricity prices.

(Reporting By Bozorgmehr Sharafedin, Canan Sevgili, Francesca Landini, Tsvetelia Tsolova, Gergely Szakacs, Alan Charlish, Stine Jacobsen, Ingrid Melander, Luiza Ili, Nora Buli, Susanna Twidale, Kylie MacLellan, Forrest Crellin, Isla Binnie, Kate Abnett, Joseph Nasr, Robert Muller, Giuseppe Fonte, Benjamin Mallet, Stine Jacobsen, Angeliki Koutantou, Anna Koper, Alan Charlish; Editing by Aurora Ellis, Susan Fenton, David Evans and Jan Harvey)