Energy bills are once again forecast to sky-rocket after Christmas as the government scales back the help it initially promised to households.

Despite a firm pledge from new PM Liz Truss to provide struggling households with two years of price guarantees for their gas and electric bills, new Chancellor Jeremy Hunt dramatically slashed that to no more than six months of support in his latest financial plan for the country.

The average home, using an average amount of energy is now facing bills of more than £4,000 by the spring - with further fluctuations likely - as bills return to being controlled by Ofgem's price cap next year.

So when bills go up - or come down - and when?

What is happening?

The government had initially pledged to guarantee the price of people's energy bills for the next two years - which would have been done by borrowing enough money to bridge the gap between the price households would pay for gas and electric and the actual price being charged by UK suppliers.

This lifeline came into effect on October 1 and, while homes have seen their bills rise between 25% and 30%, the move has artificially kept gas and electric bills much lower than initially forecast if it had been left to the price cap to dictate how much we pay this winter.

However this extra help, it has now been announced, will only now be available until early next year. After this, households will return to having their gas and electric prices controlled by the energy price cap and the goverment will instead only offer help after April for those it feels will need it most.

What is the price cap?

The price cap on energy bills was introduced in January 2019 as a way to ensure that homes who aren't bill-savvy, and used to switching between suppliers for better prices, are not ripped off by energy suppliers.

Energy regulator Ofgem sets the maximum price that households have to pay for every unit of gas and electricity and this cap is calculated based on the wholesale price of gas and electricity and also includes allowances for tax, charges paid to the energy networks, green levies and social payments.

It is primarily the price of energy - driven up by the war in Ukraine - combined with debt that suppliers had to take on when other energy firms went bust that has led to such sky-high rates during the last 12 months.

So when will bills rise now?

The price cap used to be assessed every six months but a decision was made earlier this year to revisit it quarterly - or every three months - instead so that prices can reflect more quickly changes in the energy market.

This means, when the government removes its help at the end of winter, homes will be returned to prices set by the price cap from April.

But with updates every quarter this means bills will not only change ready for April, but also again in July and ahead of next winter in October 2023, then January and so on.

What will I have to pay?

With such volatility in the markets - and the war in Ukraine adding additional uncertainty - it is difficult to firmly predict exactly whether bills will face rise after rise next April, July and October, or whether they're more likely to go up and come down before possibly rising again ahead of next winter.

But forecasts, released after the government announced it was pulling help for all households after March, suggest that average sized bills, for average sized homes, using average amounts of energy could go up by more than 70% to £4,350 next April when customers return to prices set by Ofgem and the price cap that come without any extra government buffer to soften the blow.

Early predictions by Cornwall Insight suggest that bills may then come down 15% in the summer to around £3,700 a year from July - while the remainder of next year and next winter remains more uncertain.

But as with all predictions, these are average forecasts to give everyone an idea of what's coming - so bigger homes using more energy will see their bills rise faster and those who use less won't be faced with paying quite as much.

What help will there be?

While admitting the government cannot cushion the cost of energy bills for everyone for two whole years, new Chancellor Jeremy Hunt has pledged to now investigate targeted support for those who will struggle to pay their bills from April when the government withdraws its help.

However consumer experts, who have likened April's predicted costs to 'a second mortgage', suggest that help may need to extend way beyond low-income households as many millions of middle-income homes will struggle to afford average annual bills of between £4,000 and £5,0000.

Until then, the £400 energy support scheme remains in place this winter for everyone, with six monthly instalments trickling through between October and March to help customers manage their bills.

While a second cost of living payment for eight million low income households is also arriving next month. This will give those claiming means-tested benefits, including Universal Credit, £324 in cash which they won't need to pay back.

Money has also been sent to those claiming disability benefits while extra help for those claiming winter fuel payments is also in the pipeline before the end of the year.