Hot water bottle or electric blanket – what's best and cheapest for keeping you warm in bed?

Turning down your heating at night has become the go-to option to help lower your energy bills, but what about those chilly nights when an extra blanket and bed socks won't keep the cold at bay?

We've number-crunched the energy costs and compared the pros and cons of hot water bottles, electric blankets and heated throws.

Should you buy a hot water bottle? 

Cost to buy: Approx. £6-£35

Cost to run: Approx. 1.1p-1.4p per hour*

*Based on the initial cost of 3.5p-4.4p to boil a kettle with enough water to fill a 1.7L hot water bottle up to two thirds of its capacity, and then using the hot water bottle for three hours.

Pros:

• Uses the least energy of the options we've compared
• Cheap to buy
• Simple and low-tech choice with no wires or plugs

Cons:

• Will cool down enough that it won't be as effective after around three hours
• Won't heat up your bed evenly
• Chance of scalding your hand while filling it up

You might have heard that kettles use a lot of energy, but you'll actually use less energy than the cost of running an electric blanket or heated throw if you use a kettle to fill your hot water bottle. That's as long as you only boil as much water as you need. Most manufacturers recommend filling hot water bottles to two thirds of their capacity.

A hot water bottle might not keep you warm throughout the night, though. Our tip from testing hot water bottles is to spend more on a thicker cover rather than splashing out on an expensive bottle. 

It's also important to wait for the boiling water to cool for at least five minutes before pouring it in. Boiling water will degrade the inside of the hot water bottle, leading to a much higher chance of the bottle bursting while you're using it.

Should you buy an electric blanket? 

Cost to buy: Approx. £40-£150

Cost to run: Approx. 2p-7p per hour

Pros:

• The best blankets distribute heat evenly
• Useful timer function means you only need to have it turned on for as long as you need

Cons:

• More costly upfront than a hot water bottle
• Our tests revealed you can feel the wires running through some blankets 

Although more expensive to run per hour than a hot water bottle, some of the electric blankets we've tested (see our reviews of the best electric blankets) aren't too heavy on energy use. Several of those we tested cost as little as 2.6p per hour to run on their hottest settings, and you can set the timer to switch off the blanket automatically after a few hours.

Electric blankets are designed to be fitted to your mattress underneath your sheet, so your bed should feel the same as usual but with extra heat coming up from underneath you.

That's if you get a good one though. Our tests found some electric blankets that distribute heat unevenly and have annoying wires you can feel through your bedsheet.

Electric blankets can cost more than £100, so it's worth doing your research first to avoid paying out more for a less-than-satisfactory night's sleep. 

Should you buy a heated throw? 

Cost to buy: Approx. £60-£115

Cost to run: Approx. 2p-5p per hour

Pros:

• Can also be used to keep you warm on the sofa
• Useful timer function means you only need to have it turned on for as long as you need
• High-quality heated throws distribute heat evenly

Cons:

• Can be pricey to buy
• Some take a long time to warm up
• You can feel the wires through some
• Short cable might not stretch from the power socket to your bed

A heated throw's main job is keeping you warm and snuggly while relaxing on the sofa, but you can also use them as a heated top blanket for your bed. You just need to lay your throw either on top of your duvet, or between your duvet and you.

Our energy-use tests found that electric throws cost less to run per hour than some electric blankets, but still cost more than boiling water for a hot water bottle.

You might find it a bit stuffy in your bed with an extra heated layer on top of you, though, and some have short cables that might not reach from the power socket to your bed. We also found some throws uncomfortable, as you can feel the wires running through them.

Find out which have long cables and which cost less to run in our pick of the best heated throws.

What's best and cheapest for keeping warm in bed?

Hot water bottles have the cheapest upfront and associated energy costs but, if you can afford it, we think a high-quality heated blanket is the best option for a cosy night's sleep. 

If you've got one of the best heated blankets fitted below your bedsheet, you won't even know it's there, and it will gently spread warmth throughout your bed for as long as you need it to.

Why you shouldn't use an electric heater while you sleep

Electric heaters have been flying off the shelves since last autumn as an alternative to central heating. You can point the heater directly towards you for maximum warmth.

We definitely wouldn't recommend using an electric heater while you sleep, though. Our tests to reveal the best electric heaters found that they're much pricier to run than all of the options above (approx. 9p-83p per hour), and also leaving them unattended can be a major fire risk.

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