What’s The Difference Between a Hydronic Boiler and a Hydronic Heat Pump?

Choosing the right hydronic heating solution for your home can be difficult. So many systems seem to be doing exactly the same thing and it can be hard to pick out the meaningful differences that will help you narrow down the right option. So don’t waste your time and money installing a system that won’t suit your needs, get a simple snapshot of the differences between hydronic boiler and hydronic heat pump systems with our comprehensive post below. But before you can understand the differences between the two systems it pays to know what each of them are.

What is a Hydronic Boiler?

A hydronic boiler is a heating solution at the heart of most existing hydronic heating systems. They operate using natural gas that ignites and transfers heat to water inside the boiler which is then pumped through the hydronic heating system including radiators, underfloor heating and heated towel rails.

What is a Heat Pump?

A heat pump, much like a hydronic boiler is an essential part of the hydronic heating system. Just like a boiler, it heats water which then circulates through the house, but instead of being fueled by natural or LPG gas, a heat pump uses electricity. A heat pump also works by extracting heat from the surrounding air, similar to air conditioning. You can read more about how a heat pump works here.

The Differences

Heat Sources

While hydronic boilers use gas to heat the water and electricity to pump the water around the system, heat pumps use electricity to both heat the water and circulate the water.


Boilers are smaller and hung on the wall. An average size would be 1000mm in height by 500mm wide and 350mm deep. The size of heat pumps however, can vary depending on the brand and model, but an average size is 1000mm in height, 2500mm wide and 900mm deep. Unlike a hydronic boiler, heat pumps also require an external buffer tank and will need to be installed on the ground due to their weight.

Energy Efficiency

The most efficient type of hydronic boiler is a condensing boiler. These boilers have energy efficiency up to 90%. It’s here that hydronic heat pumps blow boilers out of the water. With energy efficiency up to 600%, heat pumps generate far more heat for your home than it uses. On top of this,  heat pumps can also offset the additional energy using PV panels and batteries, helping save you money!


Boilers are usually hung externally on a wall outside the building, but can also be installed inside with the correct pipework and fluing. Heat Pumps however, must sit on the ground and must be outside. This is because their function is all about airflow.


When installed, boilers need 1000mm of clearance in front of the system and nothing above them. This is to allow the flu emissions to escape. Heat pumps however require a bit more space,  roughly 1500mm of clearance to allow the cold air to dissipate, without it being pulled back into the rear fan unit.


Boilers emit a plume of hot air and water vapour into the open air. Think of this like steam on cold mornings. Heat pumps emit a stream of cold air from the front of the unit, propelled by a fan.

Electrical Requirements

Hydronic Boilers can plug into a standard weatherproof GPO, while heat pumps require a designated 32 amp circuit wired into the fuse box.


The Ideal Logic+ Boiler is one of the only boilers in the UK to receive Quiet Mark accreditation for its quiet operation. The 18kW boiler has a quiet noise level of 41 dB(A). Hydronic heat pumps also generate some noise when running. Current models vary in sound from 48dB to 68dB, on average quieter than the average conversation between adults (60dB). 

Which One’s Better?

The right hydronic heating system will ultimately depend on the requirements of your home and your own personal preferences. However, we at Nissl Eichert would recommend installing a hydronic heat pump for a few reasons. 

The first, and arguably most important, is from the 1st of January 2024, new gas connections will be prohibited in new home builds. Essentially, if you don’t have gas connected to your home already, you’ll need to install a heat pump as part of your hydronic heating system with gas superseded.

Heat pumps are also our preferred choice as they’re more energy efficient and utilise renewable energy sources, making them the hydronic heating system of the future. In addition to this, while heat pumps cost more to install they tend to be more durable and can reduce long-term running costs with their leading efficiency. 

Thinking of Installing a Hydronic Boiler or Heat Pump?

With nearly 4 decades worth of technical and industry experience, Nissl Eichert Heating is your ideal partner for hydronic heating installation. With our own in-house team, our qualified technicians will deliver the highest quality installation with our signature customer service. You’ll even benefit from industry leading warranties. Enquire with our friendly team today for a competitive quote or contact us with any of your questions!