Electric Heater on Low or High: Which Is Cheaper?

If you're wondering whether to run your electric heater on low or high, the answer depends on the heater's power settings, how long it operates and the amount of warmth your room requires.

A lower heat setting generally consumes less electricity per active heating hour when it genuinely reduces the heater's electrical wattage. However, that doesn't automatically mean using low mode will always cost less over an entire evening.

For example, a heater operating at 1000W for two hours consumes the same amount of electricity as a 2000W heater operating at full power for one hour: 2kWh.

A thermostat, room insulation, outdoor temperature and heating duration can all affect the final electricity consumption.

This guide explains how low and high heat settings work, compares UK running costs and helps you decide which mode may be more appropriate for your home.

Electric Heater on Low or High: What Changes?

When you select a different heat setting on a portable electric heater, you're usually changing the appliance's heating output.

Many portable heaters offer options such as:

• Low heat

• High heat

• Adjustable temperature

• Fan-only mode

• Automatic thermostat control

However, the exact behaviour depends on the heater.

Some appliances use separate heating elements or different electrical power levels. Others regulate heating through their thermostat or electronic controls.

For example, a heater might offer:

Low mode — 1000W

High mode — 2000W

These are illustrative figures. Your heater may have different power settings.

If the low mode operates at 1000W and the high mode at 2000W, the high setting consumes twice as much electricity during an equal period of continuous active heating.

But it also provides greater heating output.

Does a Lower Heat Setting Use Less Electricity?

Yes, when the lower setting actually reduces electrical power.

Electricity consumption is calculated using:

Power (kW) × operating time (hours) = electricity used (kWh)

For example:

A 1000W heater operating continuously for one hour consumes:

1kW × 1 hour = 1kWh

A 2000W heater operating continuously for one hour consumes:

2kW × 1 hour = 2kWh

Therefore, the lower-power setting consumes less electricity over the same active heating duration.

However, electricity use over a complete heating session may differ because the heater's thermostat can switch the heating element on and off.

For a detailed explanation of heater wattage, read our How Many Watts Does an Electric Heater Use? UK Guide.

How Much Does a Heater Cost on Low vs High?

Running cost depends on your electricity tariff.

The calculation is:

Power (kW) × operating time × electricity unit rate = estimated cost

For this example, we'll use an illustrative electricity price of 25p/kWh.

These examples assume continuous operation at the stated power.

Actual consumption may be lower when thermostat cycling reduces the time the heating element is active.

Using UK electricity rates

For a more realistic calculation, replace the illustrative rate with the unit price shown on your electricity bill.

Ofgem publishes average electricity unit rates under the energy price cap, but your actual tariff may differ depending on your supplier, region and payment method.

You can check the latest rates on the Ofgem energy price-cap unit rates and standing charges page.

For a broader discussion of running costs, explore our Are Electric Heaters Expensive to Run in the UK? guide.

1000W vs 2000W: Running Cost Comparison

Comparing 1000W and 2000W helps explain the relationship between electrical power and heating cost.

A 2000W resistance heater provides approximately twice the heating output of a 1000W resistance heater when both operate continuously at their respective rated heating powers.

However, whether the 2000W setting costs more to maintain a particular room temperature depends on how long it needs to operate.

For instance, a higher-power setting may reach the target temperature sooner and then cycle off.

That is why comparing total kWh used, rather than simply hourly wattage, provides a more meaningful picture of cost.

Does High Heat Warm a Room Faster?

Generally, a higher-power heating mode can warm a room faster than a lower-power mode, provided the heater is operating correctly and the room conditions are comparable.

A 2000W heater produces more heat per active hour than a 1000W heater.

However, several factors affect how quickly the room warms:

• Room volume

• Insulation

• Windows and glazing

• Draughts

• Outdoor temperature

• Air circulation

• Starting room temperature

• Thermostat controls

A poorly insulated room may lose heat quickly, reducing the benefit of additional heating output.

Higher wattage doesn't guarantee that every room will reach a particular temperature within a fixed time.

Can Low Heat Cost More Over a Longer Period?

Yes, a lower-power setting can consume more electricity overall if it operates for sufficiently longer.

Consider two hypothetical heating sessions.

Scenario A: Low heat

A 1000W heater operates continuously for four hours.

1kW × 4 hours = 4kWh

At 25p/kWh:

Total cost = £1.00

Scenario B: High heat

A 2000W heater operates at full power for one hour.

2kW × 1 hour = 2kWh

At 25p/kWh:

Total cost = £0.50

In these examples, the shorter high-power session costs less because it consumes fewer total kWh.

However, these sessions don't necessarily provide the same comfort over the same period. The second scenario may leave the room unheated for the remaining three hours.

To make a fair comparison, consider the total energy needed to maintain a similar comfortable temperature for the same duration.

The key principle is:

Lower wattage doesn't always mean lower total electricity consumption.

How Does a Thermostat Affect Electricity Use?

A thermostat regulates heating according to a selected temperature.

Suppose you set your heater to 21°C.

Depending on the model, the appliance may:

1. Monitor the temperature near its sensor.

2. Operate the heating element while additional heat is required.

3. Reduce or stop heating as the selected temperature is approached.

4. Resume heating when the sensed temperature falls sufficiently.

This process is commonly called thermostat cycling.

The thermostat can affect the proportion of time the heating element operates, which influences total electricity consumption.

A 2000W heater doesn't necessarily consume 2kWh during every clock hour that it remains switched on.

If its heating element is inactive for part of that hour, total energy consumption can be lower.

For more information, read our How Does a Thermostat Work on an Electric Heater? guide.

Should You Use High Heat First, Then Switch to Low?

Using high heat initially and then switching to a lower mode can be a practical approach in some situations.

For example, you might use a higher setting while bringing a cold room toward your desired temperature, then select a lower setting if it can maintain comfortable conditions.

However, this strategy doesn't guarantee electricity savings.

For a conventional resistance heater, the total energy required depends largely on how much heat the room needs and loses.

A thermostat-controlled heater may already regulate heating automatically.

When high heat may be useful

• The room is initially cold.

• Faster warming is desirable.

• The heater is designed to support the selected mode.

• The room's heating demand exceeds the lower mode's output.

When low heat may be sufficient

• The room is already comfortable.

• Heating demand is relatively modest.

• The room is well insulated.

• A lower output can maintain the desired temperature.

Follow the manufacturer's operating instructions rather than assuming every heater should use the same sequence.

Does Room Insulation Change the Best Setting?

Yes. Insulation can influence how much heat is required to maintain a comfortable room temperature.

A poorly insulated room may lose warmth through:

• External walls

• Windows

• Roofs

• Floors

• Doors

• Draughty openings

If heat escapes rapidly, a lower-power mode may struggle to maintain the selected temperature.

In a well-insulated room, the same lower-power mode may be sufficient.

This doesn't change the electrical wattage of the heating element. It changes the room's heating demand and potentially the heater's operating time.

Energy Saving Trust provides practical advice on draught-proofing your home.

For more information about heater suitability, read our What Size Electric Heater Do I Need? UK Guide.

Are Ceramic Heaters Cheaper on Low Mode?

Ceramic heaters aren't automatically cheaper to operate simply because they use ceramic heating technology.

A ceramic heater operating at 1000W consumes approximately 1kWh for every continuous hour at that power.

A conventional electric resistance heater operating at the same 1000W also consumes approximately 1kWh over the same period.

The difference between models may involve:

• Heat distribution

• Fan operation

• Thermostat controls

• Heat settings

• Noise

• Design

• User comfort

A ceramic heater with useful controls may help manage heating, but ceramic technology alone doesn't guarantee lower electricity consumption.

Read our Ceramic Heater vs Fan Heater UK Comparison for a more detailed explanation.

Which Heat Setting Is Better for a Bedroom?

The appropriate heat setting depends on the room's heating requirements and the heater manufacturer's instructions.

For example, a lower mode may provide adequate supplementary warmth while you're awake in a well-insulated bedroom.

However, heater placement and safe operation are especially important around:

• Bedding

• Pillows

• Curtains

• Clothing

• Furniture

• Carpets and rugs

Electrical Safety First recommends keeping portable heaters at least one metre away from combustible materials and advises against leaving them operating overnight or unattended.

A thermostat or timer doesn't make unattended sleeping use automatically safe.

For more guidance, read our Portable Electric Heater Safety and Placement Guide.

You can also consult Electrical Safety First's portable-heater safety guidance.

How to Avoid Unnecessary Heater Electricity Use

Choosing between low and high heat is only one part of managing electricity consumption.

Several practical habits can help avoid unnecessary heating.

Use a Comfortable Thermostat Setting

Avoid selecting a much higher temperature than you actually require.

Control Operating Time

Use the heater while supplementary warmth is needed, following its safety instructions.

Reduce Draughts

Seal avoidable gaps around windows and doors while maintaining necessary ventilation.

Improve Heat Retention

Better insulation can reduce the amount of heat required to maintain room temperature.

Use Suitable Heating Output

Choose a heater that can meet your room's heating needs without unnecessary operation.

Keep Airflow Unobstructed

Follow the manufacturer's clearance instructions and avoid blocking air intakes or outlets.

Check Your Electricity Tariff

Calculate running costs using your actual pence-per-kWh rate.

For a complete explanation, read our How to Use an Electric Heater Efficiently in Winter guide.

Shopsyde 1500W Portable Electric Heater

The Shopsyde 1500W Portable Electric Heater with Thermostat, Oscillation, Timer & Remote Control offers convenient supplementary heating with adjustable controls.

Key features

• Up to 1500W heating power

• Ceramic heating

• Digital thermostat

• Multiple heat settings

• Oscillation

• Timer

• Remote control

• Portable design

At continuous full 1500W output, the heater consumes approximately 1.5kWh per hour.

If your electricity rate is 25p/kWh, the illustrative full-power running cost is:

1.5 × £0.25 = 37.5p per hour

Actual consumption depends on operating mode and thermostat cycling.

The exact wattage of each lower heat setting should be confirmed from the product specifications.

View the Shopsyde 1500W Portable Electric Heater →

Shopsyde 2000W Portable Electric Heater With Humidifier

For customers seeking greater maximum heating output, Shopsyde offers the 2000W Portable Electric Heater with Humidifier, Thermostat, Timer & Remote Control.

Key features

• Up to 2000W heating power

• Thermostat control

• Timer

• Remote operation

• Built-in humidifier

• Portable design

At a continuous electrical draw of 2000W, electricity consumption is approximately 2kWh per hour.

Using an illustrative 25p/kWh rate:

2 × £0.25 = 50p per hour

Actual consumption may vary with operating modes, thermostat cycling and auxiliary functions.

The 2000W model provides greater maximum heating output than the 1500W model, but the right choice depends on the room's heating requirements.

View the Shopsyde 2000W Portable Electric Heater →

Explore more options in our Shopsyde Portable Electric Heaters collection.

Electric Heater Low vs High: Quick Comparison Checklist

The most useful comparison is the total kWh required to provide similar comfort over the same period, rather than simply the hourly wattage.

The Bottom Line

So, is it cheaper to run an electric heater on low or high?

Low mode generally costs less per active heating hour when it uses fewer watts. However, the cheapest way to maintain a comfortable room temperature depends on the heater's controls, total operating time and the room's heat loss.

High heat may warm a cold room faster, while low heat may be sufficient once the room is comfortable.

The key is to understand the difference between instantaneous electrical power and total electricity consumption.

Use a suitable heating mode, sensible thermostat settings and appropriate operating times rather than assuming low or high is always the cheapest choice.

For portable heating options with adjustable controls, explore the Shopsyde Electric Heaters collection.