It's summer: why is your energy bill increasing?

You'd expect your biggest energy bills to be in winter, when you're tucked up indoors with the heating turned up and lights on. But if you're one of the many customers seeing their bills increase this summer, we reveal some of the reasons why.

Energy price rises are one of the main culprits. Wholesale prices are up by 50% or more compared with last year and several energy companies have increased their prices.

Changes in how we entertain might be at play, too. People rushed to buy hot tubs in last year's heat wave and electric patio heaters have been popular throughout lockdown for outdoor gatherings when indoor entertaining was off limits.

If you've spotted your bill soaring, switching to a cheaper deal will help. You could save up to £293 per year by switching if you're currently on an energy tariff in line with the price cap.

Keep reading to see the top five cheapest energy deals in June 2021.

Compare gas and electricity prices using Which? Switch, our free and independent energy comparison website, to find out how much you could save on your energy bills.

You can also phone us on 0800 410 1149 or 01259 220235.

Why are energy prices rising?

Wholesale prices (the prices energy suppliers pay when buying power and gas for their customers) have increased a huge amount since summer 2020:

• Gas wholesale prices are up 127%
• Electricity wholesale prices are up 49%.

Between August 2020 and February 2021, according to data from energy regulator Ofgem. Energy companies are reporting that prices have continued to increase since them.

At the start of this year, cold weather and lockdowns meant that we were all at home more and using more power. Other countries were in the same position, so there was more competition to buy gas, pushing up prices.

As the cold weather continued into April and May, gas supplies in Europe were left depleted.

Electricity prices are partly linked to gas prices, because we use gas to generate some of our electricity. Some nuclear power stations were offline for maintenance earlier in the year and it was also less windy than the same time in 2020.

Increased network and policy costs, and suppliers looking to recoup bad debt that customers can't pay owing to Covid-19, may also be behind rising prices.

If you have a fixed energy tariff, your rates won't change until your contract ends. If you have a variable tariff your company will notify you if it's changing its rates.

Bulb, Octopus Energy (including Affect Energy, Co-operative Energy, Ebico, M&S Energy and London Power) and Pure Planet have all announced price increases to their standard tariffs recently.

Keep reading to see the cheapest gas and electricity deals this month or see 10 more ways to save on energy bills.

How much is your hot tub costing?

Hot tubs became a popular garden feature in 2020. Some are wood-fired, while many are electric.

If you use a medium-sized electric hot tub that seats around four people three times a week, you could add at least £20 to £30 a month to your energy bills for heating costs.

With the cost per kilowatt hour (kWh) of electricity 50% more expensive with some energy deals than others, costs could spiral even faster.

Keep costs in check by:

• Using an insulated cover - around 60% of the heat will escape through the surface
• Adding insulation between the shell and cabinet if it's not already there
• Cleaning the filters - your tub will have to work harder if filters are dirty.

See more tips to cut the running costs of your hot tub.

Pricey electric patio heaters

If you've bought a electric patio heater to keep warm outside until late in the evening, then this will be adding to your electricity bill.

They're typically 2kW or 3kW, meaning that they will use this amount of electricity per hour. For comparison, a 55-inch OLED TV uses around 115W per year (based on four hours' watching per day), according to our testing.

Run your 3kW heater while friends are round for the evening and it could cost you £2.85 for five hours (on British Gas' standard tariff, which is set at the level of the price cap).

That might not seem like much, but if you sit out under your heater once a week in May, June, July and August, it could add around £45 to your electricity bill.

But choose the cheapest tariff and it'll cost closer to £32.

Keep costs in check by:

• Using a patio heater only if essential - grab a jumper and blanket first
• Choosing the most efficient model you can
• Don't use a heater designed for indoors outside - they work by convection, so the heat will be lost in your surroundings.

Find outif patio heaters are worth it.

Save money by switching energy supplier

All of the top five widely available deals will save at least £200 per year compared with the level of the price cap.

Savings are based on a household using a medium amount of gas and electricity. If you use more or less than this, your costs and savings will be different.

Use Which? Switch to compare gas and electricity prices using your exact usage for the most accurate savings.

Top five cheapest energy supplier deals in June 2021

All tariffs are for fixed direct debit payment and paperless bills. Data is from Energylinx and correct on 22 June 2021.*

Find out how to switch energy supplier in easy steps.

Which? energy pricing research

*Prices are based on widely available dual-fuel tariffs, paying by fixed monthly direct debit, with paperless bills.

Energy use is based on Ofgem's annual average figures for a medium user (12,000kWh gas and 2,900kWh electricity).

Comparisons are based on the current price cap, correct at 1 April 2021. Prices given are averages across regions, rounded to the nearest whole pound.