Historic Buildings
August 30, 2023

The BBC Was Right – Heat Pumps Aren’t a Silver Bullet. So Let Us Help You Choose Wisely

A recent BBC article, The truth about heat pumps and the power needed to run them, might sound like the kind of exposé a sustainable building design business like ours could do without.

But nothing could be further from the truth. We’ve long explained to our clients and to the market that achieving energy-efficient and sustainable buildings is much more complex than just installing fashionable energy-saving technologies and calling the job done. There is no silver bullet.

Indeed, installing a solution like a heat pump without regard to the thermal characteristics of the building - insulation, ventilation, airflow - and the interaction with other technologies and services can result in conflicts that actually increase energy consumption and running costs.

Here’s what you need to look out for if you’re considering investing in heat pumps (with a few myths debunked along the way!)


Rip out the radiators? Read this first!

Let’s start with room heating.

The mindset here is often that because heat pumps operate at a lower hot water flow temperature than gas boilers, you need to install larger radiators.

However, it often doesn’t work like this. Factors like existing radiators’ unused capacity, as well as the other thermal characteristics of the room, can work together to substantially accelerate a heat pump’s achievement of the desired temperature, or agree a slightly lower temperature in the room on very cold days, use less energy wearing slippers and jumpers.

But – and this, again, is where the prevailing mindset falls down – only a precise, room-by-room heat loss calculation, carried out by a qualified engineer, will determine if each radiator is or isn’t sufficient, and if not what’s its limits.


Know how heat pumps are evolving

We are now seeing heat pumps that use propane (R290), a refrigerant with a very low global warming potential (GWP), to attain a higher hot water temperature, through a heat exchange.

This enables heat pumps to directly hold their own against gas boilers, but – once again – it’s no instant panacea.

Only careful investigation and detailed calculations can ever determine whether a heat pump will be a suitably energy-efficient solution for the environment in question, in truth the hotter the heat pump water the lower its efficiency is.


Heat pumps = insulation costs: a false premise

Here, the mindset is frankly back to front.

To maximise the efficiency of any heating source – not just heat pumps - you need a well-insulated building. It’s far cheaper and more environmentally friendly to prevent heat loss in the first place than to generate heat to replace that loss, whichever method is used.

What heat pumps will highlight, however – if installed properly - is the need to understand the effectiveness of your current insulation and where it might need to be improved.

And that’s where a skilled thermal analysis of your property can potentially save you money, as it will ensure you’re not spending money unnecessarily on over-insulating that can cause overheating in the summer.


Small changes can make a big difference

Human behaviour, too, can make a big impact on the energy efficiency of any form of heating - and it’s something many installers should explain to their customers more thoroughly.

For example, closing curtains on the sunny side of the building during hot weather can minimise heat build-up during the day, while opening windows in the late evening and early morning can help cool it during hot summer spells.

Work with the technology, not against it.


Heat pumps – do they cost more to run than gas?

Guess what – it’s not black and white.

Firstly, you can power heat pumps from surplus electricity generated in your building using photovoltaic solar panels and similar. This alone swings the cost of energy consumption strongly in heat pumps’ favour.

Secondly, heat pumps generate far more heat than the electricity used to power them. When you look at the seasonal coefficient of performance, which measures efficiency of heat out versus energy in, a heat pump averages 350-400% compared to just 90-94% for a gas boiler.

And thirdly, unlike gas boilers, heat pumps work better in higher outside temperatures, so if you have a summer hot water and heating loads it pays back much quicker than gas, which is at the same efficiency all year around.

But again, a note of caution: key to ensuring heat pumps work well is making sure they are designed and installed correctly for the size of the building.

Just installing a heat pump where and how you think it might work best could cost you dearly, later on .


Low emissions (the science proves it)

Cost and performance apart, heat pumps can also dramatically reduce emissions.

Here’s the science. For a (typically) 92% efficient gas boiler, you’re looking at CO2 emissions of approximately 200 grams per kilowatt hour (kWh).

With a heat pump, working from a typical seasonal coefficient of performance of 3, and using the average grid emissions of160g/kWh, CO2 emissions would be approximately 53g/kWh. That’s a 66% reduction! AND why we must look to use them to save our planet, if possible.


An answer to all ills? Ask us first

So, heat pumps are a miracle cure for carbon emissions, right?

Wrong. Because at the risk of labouring the point, how a heat pump performs, how much it emits, and how much money it saves you, is down to how it interacts with the room, the building, and the thermal characteristics of each.

That’s what we measure to ensure we install the right heat pumps for the right environment – and sometimes decide against them – every day.

And that’s the truth about heatpumps and how much it costs to run them!


Get in touch today to find out more about how we can keep your costs down and your sustainability high by choosing the right energy-efficient heating and ventilation technologies from the start.

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