Should You Leave Your Heating On Constantly or Use On/Off Cycles?

When it comes to home heating, one of the topics that is debated the most is whether it's best to leave your heating on constantly or turn it on and off, or turn the thermostat up and down, as needed. Homeowners often hear conflicting advice, and with rising energy costs, the stakes for making the right choice have never been higher. In this blog, we'll break down the science and the facts behind both approaches, exploring the best practices for both traditional boilers and modern heat pumps.

‍The Constant Heating vs On/Off Debate: An Overview

The core argument is simple:

Leave the heating on constantly: The idea here is that maintaining a consistent temperature avoids the energy spike required to reheat your home from cold.

Turn heating on and off as needed: This method assumes that heating only when necessary reduces energy waste.

While both sides have valid points, the right choice depends on several factors, including your heating system, home insulation, and personal preferences.

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How Traditional Boilers Handle Constant vs On/Off Heating

‍The Case for Constant Heating with Boilers

In older homes with poor insulation, maintaining a constant temperature can sometimes seem more efficient. This is because traditional boilers operate best when maintaining steady water temperatures rather than working hard to reheat cold spaces. The boiler will get a really hot water flow temperature through the system to heat the rooms quickly, but modern condensing boilers work best at lower flow temperatures when condensing is made possible (boosting the efficiency).

‍The Case for On/Off Heating with Boilers

For most well-insulated homes, turning the heating on only when needed is far more efficient. Modern condensing boilers are designed to be most efficient when operating in short bursts rather than constant low-level operation.

How Heat Pumps Handle Constant vs On/Off Heating

Air source heat pumps (ASHPs) work differently from traditional boilers. They extract heat from the outside air and transfer it into your home, operating most efficiently at lower, consistent temperatures.

The Case for Constant Heating with Heat Pumps

Heat pumps excel in maintaining a consistent temperature over time. Running them constantly at a lower temperature reduces strain on the compressor and improves efficiency.

The Case for On/Off Heating with Heat Pumps

Unlike boilers, heat pumps are less efficient when forced to cycle on and off repeatedly. However, in some cases, turning them off for extended periods (e.g., overnight) can offer savings.

Factors That Influence the Best Approach

Do Heating Zones and TRVs Really Save Energy?

Heat naturally moves from warmer spaces to cooler ones, this is the second law of thermodynamics, and this principle plays a key role in how your heating system will behave. When you turn off the heating in certain rooms or zones, using a Thermostatic Radiator Valve (TRV) or zoning controls, the heat from the actively heated areas will inevitably seep into these colder spaces, through doors, internal walls or just through open spaces or hallways. This transfer forces your heating system to work harder, to maintain the target temperature, in the heated zones, which increases the energy demand and potentially reduces or cancels out any perceived savings from turning off the heat in unused rooms.

In some cases, shutting off heating in specific rooms may result in negligible or even negative energy savings, especially in homes with poor insulation. With a heat pump, the situation becomes more complex. TRVs work by restricting water flow through a radiator in order to reduce the heat output. By restricting water flow, it disrupts the ability of the heat pump to distribute heat evenly throughout the system. This restriction not only reduces efficiency but can also place unnecessary strain on the heat pump’s compressor, potentially shortening its lifespan. 

While TRVs and zoning systems can offer benefits in well-designed heating systems, they need to be used thoughtfully to prevent unintended inefficiencies and increased energy consumption. Often the more simple the system is, the better, where this is possible. 

‍Smart Thermostats: A Game-Changer

Smart thermostats, such as Nest, Hive, or Tado, can make a significant difference to how efficiently you use your heating system. These devices are able to learn your schedule, monitor outside temperatures in some cases, and adjust your heating patterns inside the home automatically.

• Optimised Schedules: Only heats the home when it is needed.
• Remote Control: Adjust settings from your phone.
• Zoning Options: Heat specific rooms independently.

The heat pumps will come with their own smart thermostats. It is best to use the heat pump manufacturer thermostat, as it directly influences the heat pump and flow temperature. The existing thermostats for multiple zones become on/off switches when paired with the heat pump thermostat. 

Which Method is More Cost-Effective?

Energy Efficiency Tips for Both Methods

Invest in Insulation: Proper loft, wall, and floor insulation make a massive difference.

Use Smart Thermostats: Automate and monitor your heating for efficiency.

Optimise Heating Zones: Only heat the rooms you're using.

Service Your System Regularly: Regular maintenance ensures peak efficiency.

Final Thoughts

When trying to decide whether to leave your heating on constantly or use on/off cycles doesn’t have a one-size-fits-all answer unfortunately. The ideal approach depends on your heating system, insulation, and home design.

For traditional boilers, intermittent heating tends to work in well-insulated homes. For heat pumps, steady, low-temperature operation usually works best.

If you're unsure, contact our professionals who can help assess your home and heating system to recommend the most efficient and cost-effective approach, or arrange a home assessment. 

By understanding how your system operates and optimising your approach, you’ll save money, reduce energy waste, and keep your home warm and comfortable all year round.

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