Key takeaways

• Discover how a personal commitment to decarbonisation led to replacing a nearly new gas boiler for a bold, eco-friendly upgrade.
• Uncover the hidden emissions costs of gas heating revealed by a detailed household carbon footprint analysis.
• Learn how government incentives and long-term savings make switching to a heat pump not just green, but smart financially.
• Explore the thorough evaluation of alternatives—why waiting for hydrogen or sticking with gas wasn’t the answer.
• Get a first-hand look at real-world performance data and insights that could redefine home heating in the quest for net zero.

Decarbonisation has been a personal mission of mine for years. After recently unpacking my household carbon footprint and seeing how much gas heating dominated my emissions, I felt responsible for taking action at home. Our house was only built in late 2022 – complete with a brand-new, efficient gas boiler. Replacing a barely 2-year-old boiler isn’t a typical move, but this is part of my ongoing journey to net zero.

In this article, I’ll explain why I decided to swap out that new gas boiler for an air-source heat pump, how I weighed the alternatives (including the temptation to “wait for hydrogen”), and why I ultimately landed on a Daikin heat pump over other options. This is a personal story backed by data, and I hope it offers insight into the decision-making process for those considering a similar leap.

Why replace a (fairly) new gas boiler?

Standing in front of my gleaming gas combi boiler, I had a moment of doubt: it was only installed in 2022, running at ~92% efficiency – wasn’t it too early to retire it – or at the very least pass it on to someone who may need it? However, carbon emissions were at the forefront of my mind. Burning gas for heating our well-insulated home produces 1.3–1.5 tonnes of CO₂ per year. Over the boiler’s remaining lifetime (10-15 years), well over 10+ tonnes of CO₂ would have been emitted to keep our family warm. In contrast, a heat pump running on grid electricity would emit roughly 70–80% less CO₂ per kWh of heat (around 80 g vs 280 g), cutting our heating footprint by about 1 ton of CO₂ annually. As an early adopter of a home decarbonisation mindset, I felt those emissions were something I could start eliminating now rather than a decade from now.

There’s also the bigger picture: the UK has clear signals that gas heating’s days are numbered. The government is moving to ban gas (and even “hydrogen-ready”) boilers in newbuild homes from 2025, and has considered phasing out new gas boiler sales in the 2030s. The reason is simple – you can’t hit net zero by 2050 with millions of gas boilers still firing. Heat pumps are expected to become the default heating system in new homes. So even though my boiler was new, sticking with gas felt like clinging to a technology on borrowed time.

What is a heat pump?

A heat pump is a device that uses electricity to transfer heat from a colder place to a warmer place. Specifically, the heat pump transfers thermal energy

Another motivation was financial foresight. Right now, the Boiler Upgrade Scheme (BUS) offers a generous £7,500 grant for installing an air-source heat pump. That grant, available through 2025, dramatically lowers the upfront cost of a heat pump. I realised if I waited 5-10 years until my boiler was older, that grant might no longer exist – I’d potentially miss out on thousands of pounds of support. Plus, acting now, I could take advantage of current electricity tariffs that reward smart heating (more on that later) and avoid what could be rising carbon costs on gas. In short, replacing a fairly new boiler is counterintuitive, but it aligned with my long-term energy and climate goals (and was made easier by government incentives).

Finally, I had to acknowledge an emotional component: as someone professionally invested in decarbonisation, I want to walk the talk at home. It felt odd to raise awareness about clean energy by day and then come home to a gas-heated house at night. This upgrade is part of my personal commitment – an investment in the kind of future I believe in.

Alternatives Considered: Stick, Wait, or Switch?

Before committing, I explored all the alternatives: doing nothing (sticking with gas), waiting for hydrogen, or switching now to a heat pump. Each had pros and cons:

• Do Nothing (Keep the Gas Boiler) – The default choice was to leave the new boiler in place until end-of-life. Economically, this is easiest short-term – no immediate capital outlay and gas is still cheaper per kWh than electricity. Our boiler still works flawlessly and could last another 10-15 years. However, “doing nothing” means continuing to emit ~1.4 tons of CO₂ every year from heating.  It also means locking in ongoing reliance on fossil gas. At ~6.5 pence per kWh, gas has been relatively cheap, but prices are volatile and likely to rise with carbon taxes or reduced supply. In contrast, electricity (around 20 p/kWh for grid power currently) costs more per unit but is getting cleaner and, with smart tariffs, can be cost-competitive. Sticking with gas would save me from an upfront install headache, but at the expense of higher carbon emissions and potentially higher lifetime costs (I’ll show data on this shortly). There’s also an opportunity cost – every year I delay switching, I forego the carbon and efficiency gains a heat pump would bring. Given my net-zero target, “do nothing” felt like treading water instead of swimming forward.
• Wait for Hydrogen – What about holding out for the much-hyped hydrogen boilers? In theory, hydrogen could replace natural gas in future networks, allowing us to use similar boilers with zero-carbon fuel. My current boiler isn’t officially “hydrogen-ready”, but many modern boilers can handle a ~20% hydrogen blend. The allure here is to keep using familiar gas infrastructure and possibly just swap to a hydrogen supply later. However, after a lot of research, I grew very sceptical that hydrogen heating would be practical or affordable for homes anytime soon. A huge body of evidence (54 independent studies and counting) indicates hydrogen will have no significant role in heating buildings. It’s simply too inefficient and costly to make green hydrogen for millions of homes. Even if it were technically feasible, the cost per kWh of hydrogen would likely be several times that of natural gas or direct electricity​. One recent analysis pegs hydrogen heating as at least 2-3 times more expensive than running a heat pump, when you factor in the energy losses in producing and distributing H₂​. The UK government itself has hedged on hydrogen – cancelling most of the planned trial hydrogen towns and (in new building standards) effectively ruling out hydrogen boilers in new homes because there’s “no practical way” to reconcile them with climate goals​. Waiting for hydrogen would mean burning natural gas for many more years on the mere hope that sometime in the 2030s a hydrogen network arrives – and even then, I’d likely need to buy a new hydrogen-ready boiler. In my assessment, that strategy was a high-carbon gamble. Unless some miracle occurs in hydrogen tech, betting my home’s decarbonisation on it didn’t sit right. To put it bluntly, hydrogen is not a viable option for mainstream home heating in the foreseeable future​.
• Switch Now (Heat Pump) – The third option was to bite the bullet and install an electric heat pump now, replacing the gas boiler. This has the obvious climate benefit: immediately slashing my home heating emissions by roughly 70-80%. It also “future-proofs” my home – I’d be on the solution (electric heating) that the UK and others are pushing for net zero. Financially, the BUS grant of £7,500 would bring the upfront cost down dramatically (essentially making the heat pump free or low-cost, as I’ll show). Running costs were a crucial consideration: could I heat my home on electricity without breaking the bank? The key is efficiency. Modern air-source heat pumps can reach 300-400% efficiency in seasonal performance, meaning 1 kWh of electricity yields 3-4 kWh of heat. Even at a unit price 3x higher, the math can work out in favor of the heat pump. In fact, analyses show that if electricity costs around twice the price of gas per kWh, a typical heat pump already breaks even or saves money over a boiler in total ownership cost. In the UK we’re a bit above that ratio right now, but my heat pump would have a seasonal COP around 3.3–3.7, which makes it very competitive. And if I leverage a smart tariff (like Octopus’s “Cosy” tariff for heat pumps) to run the pump during off-peak times, the effective cost per kWh can drop closer to 15p. Additionally, I plan to add solar PV in the future, which a heat pump can take full advantage of (using excess solar to heat the house or charge a hot water cylinder). You can’t do that with a gas boiler – you can’t generate your own gas on your roof!​ All these factors made switching now appealing. The downsides? The hassle of installation (new piping to integrate the heat pump, likely installing a hot water cylinder since combi boilers don’t have one, and possible minor radiator upgrades). Also, I’d be effectively scrapping a nearly new boiler – not exactly a trivial decision or one that most homeowners would make lightly. To ease my conscience, I intend to resell or re-home the old boiler (so it doesn’t end up as waste). In the end, the argument for switching now – with strong financial support and clear environmental benefit – won out.

Having decided to pursue a heat pump, the next question was: Which heat pump, and from which provider?

Comparing Heat Pump Options: Daikin vs. Octopus Cosy vs. Panasonic

I researched and obtained quotes for a few different heat pump options before making my choice. The three contenders that emerged were:

• Octopus Energy’s “Cosy” Heat Pump system – Octopus Energy (my electricity provider) has invested heavily in heat pumps and even developed their own model, the Cosy 6, built in a new UK factory. The Cosy package includes the heat pump unit, smart controls (“Cosy” app integration), and often a hot water cylinder and up to 4 smart thermostat “pods” for zoning. It’s marketed as a quiet, efficient 6 kW unit that can handle flow temperatures up to 65 °C. Octopus offers it at a very attractive price point (thanks to their vertical integration and the BUS grant) and an 8-year warranty with ongoing support/monitoring​. Essentially, it’s a one-stop shop: they survey, install, and maintain it with their in-house team.
• Daikin Altherma 3 (Monobloc) – Daikin is one of the largest and most established heat pump manufacturers globally. Their Altherma line of air-source heat pumps has a strong reputation for reliability and performance. I was quoted for an ~4kW Daikin monobloc unit (which, like the Cosy, sits entirely outside and just plumbs into my heating system – no refrigerant work needed internally). Daikin’s unit would be installed by Octopus as well (they sometimes supply Daikin units as an alternative to their Cosy, depending on stock or if the home needs a different size). The Daikin came with similar warranty terms. However, it doesn’t have the same integrated app as Cosy – it would use Daikin’s controls (and I’d likely use a third-party smart thermostat). Daikin’s brand reliability and performance stats were a big plus, and Octopus was offering it at essentially the same cost as their own Cosy unit in my case.
• Panasonic Aquarea – I also got a quote from a local installer for a Panasonic Aquarea heat pump (Panasonic’s well-regarded line of ASHPs). Panasonic’s units actually boast slightly higher efficiency on paper than both Daikin and Cosy, and are known for quiet operation. The model in question was around 7-9 kW capacity. This option, however, seemed substantially oversized for my home and came in at a much higher upfront cost (as we’ll see) since it was a more traditional install (private installer pricing, albeit with the grant applied). Panasonic is a trusted brand and their heat pumps can perform very well, but the cost difference and the fact I wouldn’t have the integrated support from Octopus made this option less attractive in the end.

Let’s dive into the performance and cost comparisons of these options. I gathered data on their efficiency (COP), seasonal performance, noise levels, and of course detailed cost of ownership. Below is a summary of key performance metrics:

Heat Pump Performance Comparison (vs. gas boiler)

As the table shows, all the heat pumps have excellent efficiency relative to a gas boiler. Even in cold weather requiring 55 °C water (for radiators), they achieve sCOPs of ~3.0–3.5, meaning ~300-350% efficient over the season. At lower temperatures (e.g. when heating underfloor or on milder days with 35 °C flow), efficiency jumps to ~4–5×. The Panasonic edged out others in specs – boasting around 4.9 sCOP at 35 °C – likely because the quoted model was a high-performance unit. The Daikin was in the middle, and the Cosy a bit lower (around 3.36–3.98 sCOP depending on flow temp). In practical terms, this means for my estimated 7,000 kWh/year heating demand, the Cosy would consume ~2,080 kWh/year of electricity, the Daikin ~1,890 kWh, and the Panasonic ~1,700 kWh.

All three can technically supply domestic hot water; Cosy advertises up to 65 °C output which is plenty for hot water tanks (and allows periodic legionella pasteurisation). Daikin and Panasonic standard models typically run up to ~55 °C efficiently; higher temps would reduce their COP or require a boost. I’m planning to keep water flow temps as low as possible (~35-40 °C day), since our radiators will be changed and oversized by 30-50%.

On noise, the numbers are fairly close: 55–60 decibels. For context, 60 dB is about the sound of a refrigerator or conversational speech. In other words, these units are quiet. Standing a few meters away, you’d hear a gentle hum or fan whir, but nothing disruptive – and certainly a far cry from the myth of heat pumps sounding like “jet engines.” (Modern units also often have night modes to drop fan speeds further in the evenings.) The Cosy and Panasonic claim a slight advantage (mid-50s dB), whereas the Daikin unit was rated ~60 dB(A). This wasn’t a big differentiator for me, but it’s nice to know none of them will annoy us or the neighbours when running.

Physically, the Daikin unit is widest but flattest, whereas the Cosy is more of a cube. Space wasn’t a major issue in our installation, but I did note the Daikin’s slim profile could tuck against a wall more easily. The Cosy’s spec includes the “4 pods” for zoning – a cool feature, as it comes with wireless thermostats/actuators that can create up to four independent heating zones in the house. In our current setup we mostly heat the whole house together, but having built-in zoning could be a plus for saving energy (Octopus bundles those pods with the install). With Daikin or Panasonic, multiple zones would require additional plumbing/controls (and cost). However, even though Cosy supports this, zoning is usually not a good option for heat pumps as they tend to work less efficiently.

Now, onto the cost comparison, which was arguably the deciding factor in choosing Daikin. I analysed the total cost of ownership for each option – including upfront investment, the BUS grant, annual energy costs, maintenance, and subsequently the net present value (NPV) over 15 years (my chosen analysis period, roughly the pump’s expected life). I also compared these to the baseline of keeping my gas boiler, and a hypothetical future hydrogen boiler scenario. Here’s a summary of the economics:

Cost of Ownership: Gas vs Hydrogen vs Heat Pumps (15-year horizon)

Looking at the table, a few points jump out:

• The heat pumps (Cosy & Daikin) come out cheaper in total lifetime cost than sticking with the gas boiler, even in this conservative scenario. For example, the Daikin’s ~£5,600 NPV cost beats the gas boiler’s ~£6,300. This is remarkable, because it counters the old assumption that “gas is always cheaper.” Thanks to the heat pump’s high efficiency and the current grant, I’m basically getting lower heating bills and comparable (or lower) 15-year costs by switching to a heat pump. In simple terms (no discounting), gas would cost me ~£8.9k over 15 years, whereas the Daikin would cost ~£7.8k – a saving of over £1,000 in today’s money. This aligns with wider findings that at roughly a 2–3:1 electricity vs gas price ratio, heat pumps can break even on total cost or even save money. And that’s before considering any future increase in carbon pricing on gas or additional savings from smart tariffs/solar.
• The Daikin vs Cosy vs Panasonic comparison: The Daikin option edges out Cosy by a small margin in cost. Upfront, both were ~£500 to me (virtually a rounding error on a home improvement budget), since Octopus priced the Daikin unit similarly aggressively to their own. The Daikin’s better efficiency means about £40/year less in running cost than Cosy, which over 15 years gave it a roughly £400–£500 advantage in NPV. The Cosy, meanwhile, was still a close second – and certainly vastly cheaper than the Panasonic option. The Panasonic heat pump, with an out-of-pocket of £4.8k, ends up with a much higher total ownership cost (£10k NPV). In fact, opting for the Panasonic would cost about £4,000 more over the period compared to Daikin. That was too big a gap for me to justify, given that the performance differences weren’t game-changing. Essentially, Panasonic’s extra efficiency couldn’t financially overcome its steep install price in my scenario.
• Hydrogen is a clear outlier in cost, as expected, a hypothetical hydrogen heating setup would be extraordinarily expensive (~£12k NPV, nearly double Daikin’s cost). Even if my current boiler could be converted for free (which it can’t), the fuel cost of hydrogen (assumed ~15p/kWh here) makes it hugely uneconomic. This reinforces the earlier point: waiting for hydrogen would likely mean paying more to emit more CO₂, which doesn’t make sense.

It was enlightening to see that the lowest-cost path (in the long run) was actually the heat pump – specifically the Daikin. If I only looked at short-term, keeping the gas boiler has zero immediate cost, yes. But over a 15-year view, that “free” boiler turns into higher operating expenses that sum to more than the cost of a heat pump. The BUS grant really tilts the scales: without it, the heat pump options would look much less attractive (e.g. Daikin would be ~£8k upfront, which would make the 15-year cost ~£13k, clearly worse than keeping gas). With the grant, though, it’s a different ballgame – essentially a heavily subsidised upgrade that pays back in both lower bills and carbon savings.

Why I Chose Daikin: Key Factors in the Decision

After weighing all of the above, I decided to go with the Daikin heat pump, installed via Octopus Energy’s scheme.

Here’s a summary of why Daikin won me over among the heat pump choices:

• Lowest Long-Term Cost: As the tables showed, Daikin offered the best economics. With virtually no upfront cost (after grant) and lower annual energy use than the Cosy, it had the lowest total cost of ownership in my case. Essentially, I’d spend a few hundred pounds now and then enjoy slightly lower heating bills every year going forward with much better thermal comfort compared to existing gas boiler. The Cosy was a close second, but its slightly higher running cost meant it wasn’t quite as strong financially. I also didn’t want to be ‘beta’ tester for the 1st generation Cosy when it comes to my heating system, given it was only launched in 2024. Since both were offered at the same price to install, it came down to whether I value a bit of extra efficiency (Daikin) or the extra features (Cosy).
• Efficiency and Performance: Daikin’s specs and real-world track record gave me confidence that it would achieve the advertised COPs (e.g. HeatPumpMonitor.org). Daikin units have been tested by many homeowners and have a solid reputation in the field. The Panasonic actually had the best specs, but again, at a large cost premium – diminishing returns for my needs. And while Octopus’s Cosy is designed to be efficient (and even capable of high-temp operation), it’s a newer product with less field data available. Some early reports I found suggested Cosy’s real-world performance was still evolving (as Octopus refines the product). By contrast, Daikin’s Altherma line is on its 3rd generation – a mature tech.
• Reliability and Support: Daikin is a known global brand with decades in heat pumps. That gave me peace of mind about reliability, spare parts availability, and finding technicians who know the system. Octopus’s Cosy, while backed by Octopus’s support, is brand new – essentially a first-generation device from a company that, until recently, was an energy retailer, not a manufacturer. Octopus does provide an 8-year warranty and monitors the Cosy remotely
• Features and Integrations: The Cosy’s main allure (aside from cost) was its integrated features: the zoning pods and the seamless integration with Octopus’s app and smart tariff. That’s a really neat package – essentially “Nest meets Heat Pump” under one roof. For a moment, I was tempted by the gadget factor of Cosy. However, my home isn’t very large and is all on one thermostat currently; multi-zone control, while nice, isn’t a huge need for us (we don’t have unused rooms to shut off, etc.). I can replicate smart scheduling with third-party smart thermostats if needed. And Octopus’s tariffs (like the Cosy time-of-use tariff) can be used with any heat pump – you don’t strictly need their heat pump to sign up. So I figured I could still leverage smart charging of the heat pump by using smart plugs or API controls with a Daikin. Daikin’s unit also has some advanced control options (weather compensation, etc.) that I’m happy to tinker with myself. In the end, efficiency beat smart features for me, but this was a close call. If I had a bigger house with more varied heating needs, the Cosy’s integrated zoning might have weighed more heavily.
• Upfront and Aesthetic: Both Cosy and Daikin were essentially zero-cost upfront, so that was a tie. The Panasonic was eliminated largely due to its ~£4.8k net cost – hard to justify spending that when I could get a top-tier heat pump for 1/10th the price with Octopus. Appearance-wise, all units are fairly modern-looking; I don’t mind the utilitarian outdoor box. The Daikin’s form factor (wider but slimmer) actually suits the side passage of my house better than the chunkier Cosy might have. A minor point, but worth noting – the Daikin can hug the wall and not protrude too much.

• Timing and Availability: I also considered the timeline. Octopus indicated they could schedule installation within a few months. They have a growing team of installers and, by their own report, are installing heat pumps at a rapidly increasing rate (20% month-on-month growth). If I opted for the Panasonic via a local installer, I might have had to wait for an available slot and coordinate multiple parties (plumber, electrician, etc.). With Octopus handling everything, it’s more streamlined. Regarding Cosy vs Daikin availability, I did ask if there were any stock constraints – it sounded like either unit could be provided. (Octopus has its own manufacturing for Cosy now, and also stocks Daikins). So no major difference there, but it was good to know I wouldn’t be put on a long waitlist.

In the end, Daikin ticked all my boxes: it’s efficient, proven, quiet, essentially free to me after grant, and will be installed with a turnkey service. The Octopus Cosy was a very strong runner-up – I applaud what Octopus is doing, and it was almost a coin toss. What tipped me was simply the desire to maximize efficiency and minimize any unknowns. Panasonic’s quote served as a helpful benchmark (and a cautionary tale that not all heat pump installs are as cheap as the Octopus route!), but it wasn’t seriously in the running once I saw the price gap.

Conclusion & Next Steps

Making the decision to replace a 2-year-old gas boiler wasn’t easy, but I’m convinced it’s the right move for the long term. The UK’s decarbonisation path means we’ll all have to switch away from gas eventually – I’m just doing it earlier, at a time when I can take advantage of generous incentives and support. By choosing a heat pump now, I’ll immediately cut our home’s carbon emissions by around 1 tonne CO₂ per year, and I’ve likely lowered our 15-year heating costs in the process (thanks to the efficiency and the grant). It’s a satisfying feeling to align financial sense with climate sense.

The Daikin heat pump installation is now in the pipeline (quite literally!). I’ve scheduled the install for later this spring, before the next heating season. The plan is to also fit a hot water cylinder (for storing heat and providing hot water, since we’re moving away from the on-demand combi setup). I’m eager to see how the system performs in real life – I’ll be monitoring the electricity usage closely and tweaking settings to optimize comfort and efficiency. Expect a future blog update where I share the installation experience and initial performance data (perhaps “Episode #3” of this journey).

Looking further ahead, I’m exploring solar PV panels for our roof, and possibly a home battery. With those in place, the heat pump’s impact becomes even more powerful: I could run daytime heating or water heating directly from solar energy, and use battery or smart controls to minimize grid use at peak times. As one heat pump enthusiast pointed out, you can’t generate and store your own gas – but you can generate and store electricity. This synergy between renewables and electric heating is, I believe, the future of home energy.

If you’ve read this far, thanks for following along this personal case study. I hope it provides a useful perspective for anyone considering making the switch. Everyone’s situation will differ (boiler age, house insulation, finances), but the overarching trend is clear: heat pumps are rapidly becoming more accessible and economically sensible, not just environmentally sensible. In the UK, schemes like BUS effectively make heat pumps a no-brainer for many homes – if you can navigate the installation process, the outcome is a win-win.

I’ll end on a reflective note: two years ago, I moved into a new home with a brand-new gas boiler and thought, “Great, we’re set for heating for a decade or more.” I never imagined I’d be voluntarily swapping it out so soon. But the world is changing fast, and so are the solutions at our disposal. Sometimes, doing what once seemed radical (like replacing a new boiler) becomes the prudent choice when you look at the trajectory we’re on. Here’s to taking bold steps on the journey to net zero – and to a future where our homes are heated cozy and clean, with technologies that would make even our 2023 selves a little surprised.

Looking ahead

Stay tuned for the next update where I’ll report on the installation and any hiccups or victories along the way, and eventually the before/after energy performance of gas vs. heat pump in my home!

Warm regards,

Professor Dawid Hanak

Sources

• https://clade-es.com/blog/how-heat-pumps-compare-to-gas-boilers/
• https://committees.parliament.uk/writtenevidence/129631/pdf/
• https://community.openenergymonitor.org/t/octopus-survey-outcome-with-11kwh-daikin-hp/26765
• https://drhanak.com/my-household-carbon-footprint/
• https://en.wikipedia.org/wiki/Heat_pump
• https://energysavingtrust.org.uk/grants-and-loans/boiler-upgrade-scheme/
• https://heatpumpmonitor.org/system/view?id=72
• https://octopus.energy/cosy-heat-pump/
• https://www.betterhomesbc.ca/products/are-heat-pumps-loud/
• https://www.daikin.eu/en_us/product-group/air-to-water-heat-pump-low-temperature/daikin-altherma-3-m-4-8kw
• https://www.energy-transitions.org/bitesize/its-in-the-charts-heat-pump-lifetime-cost-electricity-to-gas/
• https://www.theguardian.com/business/2023/dec/13/uk-government-backs-plan-ban-gas-hydrogen-ready-boilers-newbuilds-2025