Combi Boiler Vs System Boiler
Combi Vs System Boilers: Choosing the right hot water heater for your home.
Every home needs a hot water supply that is reliable and cost effective and the key element in all of this is the hot water boiler.
However, not all hot water boilers are the same and matching the right type of boiler to your domestic needs is an important element to consider.
System and Combi are the 2 most common water heater choices, but which is the best boiler option for your home and how much does a new or replacement boiler cost?
Here we look at the features, pros & cons of the combi boiler Vs system boiler.
Summary of content
- What is a combi boiler?
- What is a system boiler?
- Which is the best boiler option for your home?
- How much does a new boiler cost?
Differences between system & combi boilers
Q: What is a combi boiler?
A: It is a water heater that does not use a hot water storage tank and “instantly heats” cold water direct from the mains supply.
The water flow is constantly hot and, when used within the capabilities of the unit, will not run cold. You should look at both the power output of the unit and the flow rate of the water.
You can run your home heating off a combi boiler, but they are most often set to give priority to hot water, not the heating. This means if you are using a lot of taps (shower, bath etc.) you could notice your radiators drop in temperature.
Because of this, it is generally accepted that combi boilers are more suited to smaller properties, with one bath or shower. If you don’t all use hot water at the same time, then it could be feasible to use a combi boiler for a medium sized home.
The heating units are very often small enough to fit within a kitchen cabinet and so you don’t need a lot of space to house a combi.
So, in a nutshell, a combi can run your hot water or your heating, not both at the same time.
Q: What is a system boiler?
A: This water heater relies upon a storage tank and therefore you have a “reservoir” of hot water ready to use. However, the water has to first be heated within the tank. This can result in a short wait before hot water comes out of the taps.
Because the water is stored in a tank, which is refilled as water is used, you need to ensure that the tank is well insulated. Most modern tanks come with foam insulation already surrounding the cylinder.
You will need storage space for the hot water cylinder.
If you consume the hot water faster than the heating elements can raise the temperature on the incoming cold water, then your water can run colder if you are in a period of heavy use.
It is also possible to use an electric system boiler in conjunction with solar panels. The power from the solar pv panels can be used for the immersion heater, saving you using the mains supply.
A system boiler is well suited to larger properties with 2 or more bathrooms and central heating radiators and can supply both simultaneously.
Combi Boiler Vs System Boiler: Which is the best boiler option for your home?
Apart from the obvious cost considerations, there are a few factors to take into consideration.
Factors such as your water main supply pressure, likely simultaneous demand for hot water, home heating demands and even the size of your home are all elements that contribute to the decision making process.
For a combi, you need good mains water supply pressure, not so critical when you have a storage tank.
The biggest influence is really going to be the demand on the hot water supply.
If you have a family that is going to want hot water simultaneously (i.e. 2 showers running, someone washing dishes & the heating running), then even the best combi boiler is not going to be able to cope.
On the other hand, if the timing of water use is not simultaneous then there may be a case for a combi.
Where you have lighter simultaneous demands on the hot water, a combi is a very efficient machine, up to 97% efficient in some cases.
So when you ask which boiler is best for your home, what it comes down to really is supply & demand or timing.
How much does a new boiler cost?
Once more we have to take some things into consideration.
If it’s just replacing the boiler, then in both cases the cost is going to be lower than if you are relocating a boiler or having new pipework plumbed in.
For a relocation, or where there is going to be extra plumbing or electrical work, you really need to get a professional around to survey the work and produce a written quotation – we can help you with that here:
The price guides below are to give you a basic idea of the cost of the boilers without any “extra’s”.
How much do combi boilers cost?
|Manufacturer||Output||Fitted prices range|
|Alpha InTec2 25XE||25 kw, 88% efficient, B rated||from £600 to £650|
|Baxi 128 Combi||28 kw , 89.1% efficient, B rated||from £650 to £670|
|Worcester Bosch Greenstar 24i Jnr.||24 kw, 89.1% efficient, B rated||from £800 to £850|
How much do system boilers cost?
|Manufacturer||Output||Fitted prices range|
|Ariston GENUS HE 24||24 kw, 90.3% efficient, A rated||from £580 to £600|
|Potterton Ultra System 12kW||12 kw , 89.0% efficient, B rated||from £650 to £700|
|Vaillant ecoFIT pure 612||12 kw, 89.3% efficient, B rated||from £820 to £850|
To get an accurate price for the cost of your work, it’s going to require a home survey by a heating professional. We have access to a panel “Gas Safe” engineers that covers the mainland UK and can arrange free quotations.