How to Choose the Right Hydronic Heating Boiler or Heat Pump for your System

There are options when choosing your hydronic heating boiler, however, it is important to understand the upfront costs, running costs and limitations of each.

The reason for vastly different overall costs of each type is due to

  1. The costs of the equipment required to reach a kW requirement
  2. The cost of each energy type
  3. The difference in efficiency in how each type of energy is turned into heat energy

In this article, we will cover these topics so that you can make a more informed decision.

  1. It’s All About the KW’s – how much heat energy does your home require?
  2. Which energy options are there for a hydronic heating system?
  3. Upfront cost comparison for each boiler option?
  4. Running cost comparison for each option?

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How many kW’s does your home require to heat?

At dPP Hydronics we choose to install Bosch Boilers and equipment. Having installed hundreds of boilers from such brands as Sime, Immergas, Bosch and Baxi we can confidently say that Bosch boilers are the best. Not only are they the most efficient, but we have experienced by far the fewest problems post-installation than when we installed other brands.

Keep Calm Choosing a Boiler for Hydronic Heating is all about the kW

Knowing how much heat energy your home requires to heat to a comfortable temperature in winter is the first thing you must know so that you know which boiler to choose for your hydronic heating system.

In our industry, we use kW’s (kilowatt’s) as the number that represents how much energy is required to heat a space.

We covered how to calculate this briefly in our article  – How Does a Hydronic Heating Radiator Panel System Work

While we covered this briefly previously, it’s important to note that due to many components in the construction of a home, different people can easily calculate a different kW rating. A slightly different rating will have a negligible effect on the most important result: the comfort of your home.

If you would like to know the kW’s that your home requires feel free to send through your floor plans – we can calculate this within a day and give you a price at the same time. You can then use that info to continue your research if you wish.

Hydronic Boiler Cost Comparison Graph

What energy options do you have?

Knowing what energy options you have and about how each option has its pros and cons when used with hydronic heating, will make it easy to select a boiler for your system.

Below we’ll explore the main pros and cons of each energy type.

Natural Gas

The best all-around option – especially with a high-efficiency condensing boiler. A good 90% of hydronic systems in Australia operate on natural gas. If you have natural gas this is the best option – hands down – for all hydronic heating systems.

Bottled Gas – LPG

The best option in terms of install and ongoing cost when Natural Gas is not available. While LPG can seem like hard work, most areas that don’t have town gas have a great local supplier regularly of 45kg LPG bottles – and LPG is still going to be the best solution in terms of both install and running costs. At last check, they were under $140 a bottle delivered. You should have one connected and one spare full cylinder. When you empty one you can order a replacement so that you know you aren’t going to run out in winter.

Electric Hydronic Heating Boiler

Electric Boiler

When you don’t have any form of gas an electric boiler is an option. Running costs can be high but can be offset by solar panels. Installation costs are similar to a gas boiler for a standard-sized system. A mid to large-sized system will probably require 3 phase power and will increase the install cost by a couple of grand.

Heat Pump

A heat pump can only increase the water temperature to around 50C. This is perfect for slab heating, but panels call for 70C. To use a heat pump with panels we have to double the size of the panels due to the lower temperature. A heat pump takes ambient heat from the air and increases it to around 48C. At close to or below 0C a heat pump has no heat to increase.

The choice of the cheapest running costs. – There is a catch – The upfront purchase cost is significantly higher as a large heat pump is required for a hydronic heating system. You will likely need 3 phase power but if your system is small enough single phase may suite. Considering that you may be purchasing a heat pump as part of a build/loan, keep in mind the extra ‘cost’ could be looked at as the extra interest you might pay.

Timber & Pellet Fires

A great option when you have access to large amounts of firewood and the time to manage the fire. Adding a fire powered heating unit to a hydronic heating system will add quite a few thousand dollars to your system. Most commonly they are installed on working land such as farms, up in the mountains where there are limited services or in enthusiasts homes.

To get heat from a hydronic system, you must first have built a fire to raise the water temperature enough so that the hydronic system functions. They can be backed up by a booster, but then you’ve simply invested a lot in ‘adding’ a fire to a functioning hydronic system. If you are not trying to get off the grid and have access to gas or power then we would recommend installing a standard fireplace that will complement the hydronic heating and being independent has its advantages.


Simply put Geothermal is a Heat Pump hydronic system with additional pipework in the ground. A heat pump increases available ambient heat. If it is close to or below 0C then it has no heat to increase. With geothermal, the pipework in the ground captures the warmth of around 18C even in a -0 climate, and therefore the heat pump can do its job of increasing the water temperature to around 48C. – We do not install geothermal systems.

Other Considerations with Hydronic Heating

Combi Boilers – Instant Domestic Hot Water

A Combi boiler is a boiler that can provide domestic hot water as well as water for hydronic heating. These are a great option for a small home or single bathroom, however, there are important limitations to be aware of.

A Combi boiler has a low flow rate so when they are used as an instant domestic hot water system they are only suitable for a single hot tap being on at one time. They also need to be installed as close as possible to the hot water location so the hot water reaches the outlet quickly.

Combi Boilers – Boosted Storage Domestic Hot Water

An all in one unit that provides a boiler for the hydronic heating and domestic hot water with a storage unit. Having a storage unit means that you can provide all domestic hot water with your hydronic heating boiler. This unit can provide a home with up to 3 bathrooms with its total hot water requirements, and means you don’t require a separate domestic hot water system.

Solar Heated Water

Hydronic heating is a closed circuit so solar hot water can’t be used in a hydronic heating system. However, it can be used for domestic hot water with a combi boiler as a boosted storage system.

Solar Power

Solar power can be used to offset the your power costs of an electric fired system. Hydronic heating requires a large amount of kW’s so realistically you would never be able to generate enough kW’s from solar in winter to completely cover your energy costs.

If you have any questions please write them in the comments section below.