Gas Boiler vs Heat Pump: Which Is Cheaper to Run?
For many Fulham homeowners, the question of whether a gas boiler or heat pump is cheaper to run is not as simple as comparing one appliance with another. Running cost depends on fuel prices, system efficiency, insulation, radiator size, hot water demand, controls and how the home is used every day. If you are reviewing your heating options or need a reliable Boiler Service in Fulham, it helps to understand the practical difference between a modern gas boiler and a heat pump before making a decision. At Citywide Plumbers, heating advice should always start with the property, not just the product.
Gas boilers are familiar, compact and still common across London homes. They heat water quickly, work well with traditional radiators and are usually cheaper to install than a full heat pump system. Heat pumps, on the other hand, use electricity to move heat from outside air or the ground into the home. They can be very efficient, but they need careful design to perform well.
The cheaper option to run will usually depend on whether the heat pump can operate efficiently enough to overcome the higher unit price of electricity compared with gas. In a well-insulated home with the right emitters and controls, a heat pump can be competitive. In a draughty property with small radiators and high flow temperature needs, a gas boiler may still be cheaper in day-to-day running costs.
Gas Boiler vs Heat Pump Infographic
Use this quick visual guide to compare gas boiler and heat pump running costs, including fuel price, efficiency, insulation, radiator size and hot water demand.
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How Gas Boilers and Heat Pumps Work
A gas boiler burns mains gas to heat water for central heating and, depending on the system type, domestic hot water. In many London homes, this will be a combi boiler that provides hot water on demand without a separate cylinder. This makes gas boilers compact and convenient, especially in flats, maisonettes and smaller terraced properties.
A heat pump works differently. Instead of creating heat by burning fuel, it moves heat from one place to another. An air source heat pump extracts heat from outside air and transfers it into your heating system. Even in cold weather, there is still heat in the air, although the system has to work harder as the outdoor temperature falls.
This difference is important because a heat pump can produce several units of heat for each unit of electricity it uses. A gas boiler cannot do this because it converts fuel into heat directly. However, electricity costs more per unit than gas, so a heat pump needs good efficiency to compete on running cost.
- Gas boilers burn gas to create heat directly
- Heat pumps use electricity to move existing heat
- Combi boilers can provide hot water on demand
- Most heat pumps need a hot water cylinder
- Boilers suit many existing radiator systems
- Heat pumps need careful system design
Why Running Cost Is Not Just Fuel Price
Many homeowners begin by looking at the price of gas and electricity. This is useful, but it does not tell the whole story. Gas is usually cheaper per kWh than electricity, but a heat pump may use fewer units of energy because it is much more efficient. The final bill depends on the balance between energy price and system performance.
For example, a gas boiler might convert most of the gas it uses into useful heat, but it still has flue losses and system losses. A heat pump may deliver multiple units of heat for every unit of electricity, but only if it is designed to run at suitable temperatures. If the system has to run too hot, efficiency drops and running costs rise.
This is why two homes can have very different outcomes. One homeowner may find a heat pump cheaper to run because the house is well insulated and the system operates at low temperatures. Another homeowner may find a gas boiler cheaper because their property needs high heating output, fast hot water recovery or significant radiator upgrades before a heat pump can work efficiently.
- Fuel price affects running cost
- System efficiency changes the final bill
- Insulation reduces heat demand
- Controls influence daily energy use
- Radiator size affects heat pump performance
- Hot water habits can change the result
Gas Boiler Running Costs
A modern gas boiler can still be a cost-effective heating option for many Fulham homes. Gas boilers are especially practical where the property already has a suitable gas supply, traditional radiators, limited outdoor space or no room for a hot water cylinder. For households that need instant hot water, a combi boiler can also be convenient.
The running cost of a gas boiler depends on the boiler’s efficiency, the condition of the heating system and how the controls are used. A poorly serviced boiler, dirty system water, unbalanced radiators or old controls can all increase energy use. Annual servicing helps keep the appliance safer, cleaner and more efficient.
Gas boilers can also be cheaper to repair than a heat pump system because the technology is familiar, parts are widely available and many engineers work with them daily. However, gas prices can change, older boilers can lose efficiency and repeated repairs may make replacement more sensible over time.
- Often cheaper to install than a heat pump
- Works well with many existing radiators
- Combi boilers provide hot water quickly
- Servicing helps maintain efficiency
- Older boilers may waste more energy
- Running cost depends on usage and controls
Heat Pump Running Costs
A heat pump can be cheap to run when the system is designed correctly. The key is low-temperature heating. Heat pumps work best when they can heat the home steadily using larger radiators, underfloor heating or well-sized emitters. This allows the system to operate efficiently rather than constantly trying to produce high-temperature water.
In a suitable home, a heat pump may use much less delivered energy than a boiler. This is why heat pumps are often described as highly efficient. However, because electricity is more expensive than gas per unit, the running cost advantage is not guaranteed in every home. The system must achieve strong seasonal performance to make the numbers work.
Heat pumps may also benefit from smart tariffs, solar panels or battery storage. If a household can use cheaper off-peak electricity or self-generated electricity, the running cost picture can improve. Without those advantages, the result depends heavily on installation quality, home insulation and the heating temperature required.
- Can be efficient in well-insulated homes
- Works best with low flow temperatures
- May need larger radiators or underfloor heating
- Usually requires space for a cylinder
- Can benefit from smart electricity tariffs
- Performance depends on design and installation
Efficiency and COP Explained
When comparing gas boilers and heat pumps, efficiency language can be confusing. A gas boiler efficiency figure describes how much fuel is converted into useful heat. A heat pump is often measured using COP or seasonal performance. COP means coefficient of performance. If a heat pump has a COP of 3, it produces around three units of heat for every one unit of electricity used.
The seasonal figure is more useful than a single moment of performance. A heat pump may perform very efficiently in mild weather and less efficiently during colder periods. What matters is the average performance across the heating season. A well-designed heat pump should keep the flow temperature as low as possible for much of the year.
For running cost, the heat pump needs to be efficient enough to offset the higher electricity price. If electricity is roughly several times the cost of gas per unit, the heat pump needs strong seasonal performance to compete. That is why design, insulation and emitter sizing are so important.
| Factor |
Gas Boiler |
Heat Pump |
| Energy source |
Mains gas |
Electricity |
| Efficiency style |
Converts fuel into heat |
Moves heat from outside into the home |
| Best performance |
Well-serviced, correctly controlled system |
Low flow temperature and good insulation |
| Hot water |
Often instant with combi boilers |
Usually stored in a cylinder |
| Running cost risk |
Gas price changes and poor efficiency |
Poor design, high flow temperatures and electricity price |
The headline efficiency number should never be the only decision point. A system that looks efficient on paper can perform poorly if it is not suitable for the property.
Property Suitability in Fulham
Fulham has a wide range of property types, from period terraces and converted flats to modern apartments and family homes. This matters because heating systems must suit the building. A heat pump may be easier to justify in a well-insulated home with space for an external unit and cylinder. A gas boiler may remain more practical in compact properties with limited space.
Older London homes can have heat loss through walls, floors, roofs, windows and draughty gaps. If heat loss is high, the system must work harder to keep rooms comfortable. A gas boiler can often deliver higher water temperatures to existing radiators, while a heat pump may require radiator upgrades or insulation improvements first.
Flats and maisonettes can present additional challenges. External unit placement, noise rules, permissions, shared walls, leasehold restrictions and cylinder space all need checking before a heat pump is selected. For many properties, the best first step is a heating assessment rather than choosing a system based only on running cost claims.
- Period homes may need insulation improvements
- Flats may have outdoor unit restrictions
- Cylinder space is important for heat pumps
- Existing radiators may need upgrading
- Gas boilers can suit compact layouts
- Heat loss should be assessed before installation
Hot Water and Radiator Performance
Hot water is one of the biggest practical differences between gas boilers and heat pumps. A combi boiler can heat water on demand, which suits many London households with limited storage space. Heat pumps usually work with stored hot water, meaning a cylinder is needed. The cylinder must be correctly sized for the household’s daily use.
Radiators also matter. Traditional radiator systems were often designed for higher water temperatures. Heat pumps work more efficiently at lower temperatures, so radiators may need to be larger to deliver the same comfort. If radiators are too small, the heat pump may have to run hotter, which reduces efficiency and increases running costs.
For homeowners comparing running costs, this is crucial. A heat pump that needs major radiator and cylinder upgrades may still be attractive long term, but the upfront work must be included in the decision. A gas boiler replacement may be simpler if the existing system is already suitable and the aim is to keep costs predictable.
- Combi boilers can provide instant hot water
- Heat pumps usually need stored hot water
- Cylinder size affects comfort and convenience
- Radiator sizing affects efficiency
- Low-temperature heating supports heat pump savings
- Controls should match household routines
Installation and Upgrade Costs
Although this article focuses on running costs, installation cost should not be ignored. A replacement gas boiler is often less expensive and less disruptive than a full heat pump installation. This can make a boiler more attractive for homeowners who need a fast, practical solution or who are replacing a failed appliance during winter.
A heat pump installation may involve a larger survey, heat loss calculations, radiator upgrades, cylinder installation, pipework changes, electrical work and careful positioning of the outdoor unit. Grants may help reduce the upfront cost, but eligibility and installation requirements must be checked properly.
When comparing lifetime value, the cheapest monthly running cost is not always the whole answer. You should also consider installation cost, maintenance, expected lifespan, repair availability, property value, carbon impact and future energy pricing. A system that is slightly cheaper to run but much more expensive to install may take time to pay back.
- Gas boiler replacement is often more straightforward
- Heat pumps may require system upgrades
- Grants can reduce heat pump installation cost
- Property suitability affects total project price
- Payback depends on fuel prices and usage
- Long-term value should include maintenance
Which Is Cheaper for Your Home?
For many households, a modern gas boiler can still be cheaper or similar to run compared with a heat pump, especially where the home is not yet heat-pump-ready. This is largely because gas remains cheaper per unit than electricity. However, a well-designed heat pump can be competitive because it uses electricity very efficiently.
A heat pump is more likely to be cheaper to run if your home is well insulated, your radiators or underfloor heating are suitable, the flow temperature can stay low and you can access a competitive electricity tariff. It may also be more attractive if you have solar panels or are planning wider home energy improvements.
A gas boiler may be cheaper to run or more practical if the home has high heat demand, limited space for a cylinder, unsuitable radiators, leasehold restrictions or a need for fast hot water on demand. In these cases, boiler servicing, controls upgrades, system balancing and radiator improvements may deliver useful savings without a full heating system change.
- Gas may suit compact or harder-to-upgrade homes
- Heat pumps suit efficient low-temperature systems
- Insulation can change the cost comparison
- Smart tariffs may improve heat pump economics
- Boiler servicing can reduce wasted energy
- A property survey gives the clearest answer
Final Advice Before You Decide
The cheapest system to run is the one that suits the home, is designed correctly and is maintained properly. A new heating system should never be chosen only because one option is described as cheaper in general. Gas boilers and heat pumps both have situations where they make sense.
Before choosing, look at the condition of your current boiler, the age of the property, insulation levels, radiator performance, hot water demand, available space and your budget. If your boiler is fairly new and efficient, servicing and controls improvements may be the most sensible short-term route. If your boiler is old, unreliable or you are planning a wider renovation, comparing boiler replacement with heat pump options may be worthwhile.
It is also worth thinking about comfort as well as cost. Some homeowners prefer the fast hot water and familiar operation of a gas boiler. Others prefer the steady, low-temperature heating style of a heat pump. The right answer depends on how you live in the property.
Whether you need annual servicing, heating advice, boiler repairs or Expert Boiler Installation, Repairs & Servicing in Fulham, working with Citywide Plumbers helps you understand the real running cost options for your home before committing to the wrong system.
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