The Bumpy Road to Decarbonization: The Heat Pump Discussion

For almost everybody, it is pretty clear that our current energy system and economy need to decarbonize. There is ample evidence that we need to significantly reduce our GHG emissions to stave off potentially disastrous climate change. Evidence of this can already be seen in unusual dryness/wetness and high/low temperatures for the time of year. I genuinely believe nobody wants this to happen. But that does not make it easy to deal with the changing behavior, technology and growth outlook that this entails. A clear example of this is the discussion surrounding the heat pump that was recently started with a report by the Dutch National Environmental Database Foundation (NMD). Basically, this report stated that a heat pump is much more polluting than anybody previously thought.

This fact got taken up by a lot of people and organizations as evidence that even the prized sustainable option of the heat pump is not ‘clean’ and we should therefore go back to burning natural gas in our homes or just wait until other options like nuclear fusion are available to solve all our problems. I understand this reaction to a certain extent. We are used to specific technologies and use cases in our homes such as a natural gas boiler. These are especially prevalent in regions where natural gas was, or is, the dominant fuel like in the Netherlands, UK and Germany. Being told that we need to electrify and that this entails installing a quite expensive and bulky heat pump can be hard to digest for some, especially if it is perceived as top-down. Any evidence stating that this might potentially not be the best solution is then taken up immediately to justify waiting and not changing.

But let’s examine this claim a little further. Just a simple analysis of the workings of a heat pump compared to a natural gas boiler makes it clear that a significant CO2 reduction is just a fact. A heat pump extracts energy from its surroundings and upgrades this to useful heat with electricity. It does this with an efficiency coefficient between 3 to 5, thus generating 3 to 5 units of useful energy (heat) with 1 unit of energy input (electricity). A natural gas-fired boiler will convert 1 unit of energy input (natural gas) into 1 unit of useful energy (heat). So even if you power the heat pump completely with fossil fuel electricity, you are still more efficient by a factor of 2 or more and thus less polluting than with natural gas. Furthermore, the heat pump can be powered with renewable electricity, of which we currently have a significant share that is fast rising, while the natural gas boiler can only be powered by biomethane or hydrogen, of which we have very little and none at all at the moment. So a heat pump has a very real possibility of achieving zero emissions in the near future, which in fact it comes closer to every year, compared to the continued use of natural gas boilers.

But that is not the heart of the calculation by the NMD. The main reason why the environmental impact is high stems from the use of materials in the production process. The calculations used are giving this a factor of 11 times more impact compared to the use of materials for manufacturing a natural gas boiler, giving it a ‘weight’ of 16-37% in the Dutch new building code. This frankly makes no sense because it would mean that the materials of the heat pump used in the new building code would be the equivalent of 16-37% of the actual weight of the total building. A heat pump is a heavy machine and bulkier than a gas-fired boiler but this is simply not true. It may also use a little bit more electronics (and thus heavy and rare earth metals) in comparison but by no means is this significantly more than a normal natural gas boiler. The reason the NMD arrives at this conclusion is by assuming that the coolant used in the heat pumps is not disposed of properly and ends up completely in the environment. And because the calculations do not take into account the evident (and not denied) environmental benefit of using a heat pump as opposed to a boiler, all the negative effects of the coolant give rise to a bad score.

By itself, the coolant is indeed a quite powerful greenhouse gas. The older coolant (R410a) is 2000 times more powerful than CO2, while the newer standard used like R32 is 675 times more powerful. The future use of propane will limit this negative effect further to only 3. The study calculates completely with this R410a and, thus, the most negative case.

But is the use of even the most ‘polluting’ coolant really a problem? Not exactly. Of course, we should be careful with the use of resources and materials and enable the best possible recycling practices. This is also completely possible for heat pumps and specifically the coolant, as is now also the case with refrigerators and freezers. Assuming it all ends up in the environment is quite a stretch at best. But even if you assume the worst-case scenario, it pales in comparison with the gains over a lifetime of using a heat pump. When taking this into account, 90% of the benefit is during use. More importantly, the heat pump can be completely zero emission in a decade or so, which is very much debatable for a gas-fired boiler. So a heat pump still remains a very sustainable option to heat your home!

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Photo by Charles Black on Unsplash​