Switching from combi boiler to heat pumps

How an energy efficient hot water system can help you on the path to net zero emissions?

A vast majority of UK residents greatly underestimate the carbon emissions from gas boilers. Home heating contributes to over 38% of all UK gas use.

The first step to going carbon free is reducing the amount of fossil fuel energy your house uses.

The UK housing stock, though, is not very energy efficient, costing both residents and the climate; residential housing contributes around a fifth to our carbon emissions.

It all starts at home.
Changing energy consumption behaviour and decarbonising heating & hot water will help to tackle climate change, given the impact of the domestic heating sector on emissions.
The UK government identifies that the prerequisite to switching to decarbonised, low-carbon technology for homeowners is improving the energy efficiency of residences first – as this would lower energy used by keeping the heat in for longer. For space heating, this means improved insulation and better draught proofing.

But what about measures to improve efficiency related to the second biggest energy expense in your home – hot water?



The need for energy efficient hot water systems to reduce energy demand

As the need to switch from gas to renewables becomes increasingly urgent, modern heat pump and solar PV technologies are the government’s preferred zero direct emissions heating systems to heat UK homes (read more about grant support & other resources currently available to support the switch to renewable systems here).

However, switching from gas boilers to renewables such as air-source & ground-source heat pumps will need additional thermal storage for heating water. As most homes use combi boilers which provide hot water on demand, currently only a third of the UK residents use a separate hot water system.

Water heating takes up about 18% of the overall household energy consumption, the second largest after space heating. So even as it is ancillary to heat pumps, with the rapid heat pump adoption there will be a significant demand for additional thermal storage, and an energy-efficient hot water system will be vital to lowering overall energy demand.

Separately, as it stands, despite a slower heat pumps rollout than the 600,000/year target, 2023 saw record high heat pump installations across the UK.

This surge in uptake directly impacts UK’s overall electricity demands. The National Grid estimates that demand could double, which naturally means a rise in consumer bills, since electricity is more expensive, which could then make it more challenging to meet the net zero agenda. Installing a solar system on a new build property will make the transition to electric heating more affordable, and should help to delay the need for expensive and cumbersome grid reinforcement measures.
So while integrating solar PV along with heat pumps in homes can help take the strain off the grid, a multi-compatible, highly energy efficient thermal energy storage system, Thermino xPlus, can help bring your home’s overall onsite emissions down to zero.

The Thermino xPlus heat battery is a smart alternative to indirect hot water cylinders, and can help you transition from gas to renewables, reducing your emissions every step of the way to net zero.



A picture of combi boiler vs. heat pumps
Switching from combi boiler to renewables?

The road to net zero

Let’s say that you’re currently on a combi-boiler heating & hot water system.  With this system, the average annual gas usage for space heating & hot water is about 9600 kWh and 2400 kWh, respectively. The total carbon emissions currently amount to 2190 kgs.

When you add a Thermino xPlus and solar PV into the system, there’s a straight 60% reduction in the amount gas used from the combi, thanks to the pre-heating provided by Thermino xPlus, and water heating demand can be met by PV-generated electricity. This step cuts the emissions by about 12% over the original combi boiler system.

Then, when you introduce off-peak electricity to this system, hot water can be entirely provided by the PV + the back-up off-peak electricity, eliminating the need for gas for hot water completely. This leads to a reduction of about 20% emissions over the combi boiler system.
Finally, when you’re ready to install a heat pump, heating for hot water for taps and baths can be provided by heat pumps + solar PV entirely, bringing the onsite carbon emissions down to zero. And when the heat pump is paired with the latest heat pump promotional tariffs, such as Cosy Octopus or Ovo’s Heat pump plus, which charge electricity at 15-19p kWh (well below the standard tariff rate of 25p kWh), the running costs come down significantly, much lower than an old gas boiler.

While on this pathway, when you’re upgrading your heating system – switching from gas to solar PV and heat pumps – the transition is now more affordable and easy as there is no need to upgrade your original xPlus heat battery to make it compatible with either solar PV or heat pump, thanks to Optimino technology.

Here are a set of illustrations to understand the journey to net zero and the carbon savings with every addition:

a) Combi-boiler system

b) Thermino with PV & off-peak back up electricity

C) Thermino paired with heat pump and PV:

If you’re private homeowner or landlord looking to install Thermino heat batteries in your house, get in touch with one of the Sunamp-certified installers near your location:
Find stockist and installer – Sunamp UK