Storage heaters use electricity to store heat for later. They are often used with tariffs that offer cheaper electricity at certain times, such as overnight.
How Storage Heaters Work
A normal electric heater uses electricity at roughly the same time that it produces heat.
A storage heater works differently.
It contains material that can store a large amount of heat. Electricity heats this material during a charging period.
The heater then releases the stored heat into the room later.
In simple terms:
Charge → Store → Release
This is why storage heaters are often used with off-peak electricity tariffs.
Why Do They Charge Overnight?
Many storage heaters were designed to use cheaper electricity during off-peak hours.
Economy 7 is a common example.
It gives you two electricity rates:
- a cheaper off-peak rate
- a more expensive peak rate
A storage heater can charge during the cheaper period and then release the heat during the day.
However, the exact cheap-rate hours can vary.
So, check your tariff rather than assuming when your heater should charge.
Input and Output
Older storage heaters often have two important controls:
Input and Output
Understanding these makes traditional storage heaters much easier to use.
Input
Input controls how much heat the heater stores.
Think of it as asking:
How much heat will I need tomorrow?
A higher Input setting normally means more electricity is used during the charging period and more heat is stored.
A lower setting stores less.
So, colder weather may require more Input than mild weather.
Output
Output controls how quickly the stored heat is released.
Think of it as asking:
How quickly do I want to use the heat I’ve stored?
Turning Output higher does not create more heat.
Instead, it lets the stored heat escape more quickly.
That distinction is important.
Think of a Tank
A simple way to understand an older storage heater is to imagine a tank.
Input fills the tank.
Output controls how quickly you empty it.
If you do not put enough heat in, you may run out.
However, if you release the heat too quickly, you can also run out before the end of the day.
So:
Input = how much heat you store
Output = how quickly you use it
Why Is It Cold by Evening?
Suppose your storage heater is hot in the morning but cold by early evening.
There are two common possibilities.
First, you may not have stored enough heat.
Alternatively, you may have released the stored heat too quickly.
For example, leaving the Output high all morning can release a large amount of heat early in the day.
Then, there may be much less left for the evening.
So, ask:
Did I store enough heat?
Then ask:
Did I release it too quickly?
Why Is It Too Hot?
The opposite can also happen.
If the Input is too high for the weather, the heater may store more heat than you need.
Older storage heaters cannot hold that heat perfectly. Some will escape through the casing even if the Output is low.
So, the room may become warmer than you want.
If this happens regularly, try reducing the Input gradually.
Make Small Changes
Traditional storage heaters respond slowly.
If you change the Input today, you may not properly see the result until after the next charging period.
So, avoid changing several settings at once.
Instead:
- Make one small change.
- Let the heater charge.
- See how the room feels the next day.
- Notice when the heater starts to cool.
- Adjust again if needed.
After a few days, you should have a better idea of what works in your home.
What Is Boost?
Some storage heaters have a separate boost, convector or direct-heating function.
This works differently from stored heat.
The storage part uses electricity earlier and saves the heat for later.
A direct boost uses electricity while it is producing extra heat.
So:
Storage heating = previously stored heat
Boost = electricity being used to produce heat now
This matters because the boost may use electricity at the rate that applies when you switch it on.
Therefore, don’t assume that Boost always uses cheap off-peak electricity.
Check your heater and tariff.
Modern Storage Heaters
Modern storage heaters can be much easier to control.
Depending on the model, they may have:
- electronic thermostats
- timers
- heating schedules
- automatic charging
- fans
- better insulation
- digital controls
Some models can work out how much heat to store based on the temperature and heating schedule.
So, you may not have traditional Input and Output controls at all.
If you have a modern heater, use the instructions for your exact model rather than applying settings intended for an older heater.
Check Your Tariff
The electricity tariff is an important part of a storage-heating system.
Check:
- your peak unit rate
- your off-peak unit rate
- when the off-peak period starts and ends
- whether your heating has a separate controlled supply
For example, Economy 7 normally provides seven off-peak hours, but the actual times can vary.
Learn more: Economy 7 Explained →
Don’t Assume Economy 7 Is Cheapest
Having storage heaters does not automatically mean that any Economy 7 tariff will save you money.
You normally pay a different rate for electricity outside the cheaper period.
So, the overall result depends on:
- the peak rate
- the off-peak rate
- how much electricity you use at each rate
Therefore, compare the whole tariff rather than looking only at the cheap overnight price.
Be Careful Before Changing Tariff
This is particularly important in homes with older storage-heating systems.
Some heaters and hot-water systems are linked to special meter or switching arrangements.
So, before changing tariff or meter, find out:
- what meter you have
- when your cheaper electricity is available
- how the heaters receive power
- how your hot water is heated
If you have an unusual or older setup, speak to your supplier before changing it.
Storage Heaters and Hot Water
Homes with storage heaters often use electricity for hot water too.
For example:
Storage heaters → room heating
Immersion heater → hot water
Both may be set up to use cheaper electricity at certain times.
However, they are separate systems.
So, changing a heating control does not necessarily change your hot water.
Learn more: Immersion Heaters Explained →
If Your Heater Doesn’t Charge
If a storage heater stays cold after its normal charging period, first check the simple things.
Check:
- the heater controls
- your electricity supply
- your tariff and off-peak times
- any user-accessible switches or controls
- the instructions for your model
Do not remove covers or attempt internal electrical repairs.
If the normal controls appear correct but the heater still does not charge, get suitable professional advice.
Using Storage Heaters in Summer
If you do not need space heating, there is normally little benefit in deliberately storing heat that you do not want.
However, heaters differ.
So, follow the instructions for your model when changing seasonal settings.
Also, remember that your hot-water system may still need its off-peak electricity supply.
Keep Storage Heaters Clear
Storage heaters can become very hot inside.
So:
- don’t cover them
- don’t dry clothes on them
- keep vents and grilles clear
- don’t place objects against the heater
- follow the maker’s safety instructions
Older storage heaters are also extremely heavy. Internal work should therefore be left to someone competent to do it safely.
Key Points
Storage heaters use electricity at one time and provide heat later.
With older heaters:
Input controls how much heat is stored.
Output controls how quickly that heat is released.
So, if the heater goes cold too early, you may need more stored heat or you may be releasing it too quickly.
Also, check when your cheaper electricity applies and what your peak and off-peak rates are.
Finally, modern storage heaters can work differently. So, use the instructions for your particular model.
Next: Immersion Heaters Explained →