The Big Building Battle of the Century: Fossil Heating versus Heat Pumps

(Part II of Office Lighting is still in the works.  We digress for a discussion about heating.)

A battle is shaping up between heating buildings with fossil fuels versus using heat pumps. And it’s a BIG one, I’m not kidding.  It may be the biggest battle in building design this century. And it affects almost everything in buildings: carbon emissions, energy cost, maintenance, noise, building cost, aesthetics, safety (and this is a big one – I’ll explain in a minute), comfort, reliability, and more.

So here’s an early scorecard. We are finishing up a study comparing fossil v heat pumps in Tompkins County, the report will come out soon. So I’m not giving hard numbers here. If you are interested in the study, send me an email at imshapiro at

The comparison here is primarily for a type of heat pump called the air source heat pump. Geothermal heat pumps, also called ground source heat pumps, are another option but are not as common. Their characteristics are generally similar to air source heat pumps, but they are slightly more efficient (use less energy) and are more expensive to install.

The comparison is also intended to be honest. I am not seeking to favor heat pumps, I’d like to give an honest assessment. I believe in heat pumps, but I also believe that we will not succeed in their use unless we honestly discuss all their pros and cons.

So here’s my scorecard:

Carbon emissions:  Heat pumps use electricity, and electricity is increasingly derived from renewable sources.  In areas such as upstate New York, where a lot of our electricity is already renewable (thanks to hydroelectric, and growing solar), heat pumps win hands down.  Over time, as the grid becomes more and more renewable, it will not even be a contest.  Heat pumps – 1, fossil – 0.

Energy costs:  Energy costs are clearly lower for heat pumps if compared to oil or propane.  It’s something of a tie if the fossil fuel is natural gas.  In areas where electricity is cheap, heat pumps edge out natural gas. In areas where electricity is expensive, like NY City, natural gas can be lower in energy cost than electricity, although New York still uses a lot of oil, where heat pumps win. An interesting fact is that the efficiency of fossil heating systems have hit a limit, they cannot go higher, they have bumped up against the efficiency of 100%, it’s physics. However, heat pump efficiency can and will go higher as the technology improves, as much as 50% higher or more, further reducing energy costs (and carbon emissions, by the way). The score here is tough, I was going to call it a tie at 1-1, but I think heat pumps get the edge.  Heat pumps – 1, fossil – 0.

Maintenance:  Fossil systems really need to be serviced and inspected annually, due to the risks of poor combustion, which include poisoning from carbon monoxide and low energy efficiency.  So, the big question is, do heat pumps need to be serviced annually?  There is no big safety risk. There is a risk that heat exchangers and filters will get dirty, but they need to get really dirty before there is a measurable loss in efficiency, so cleaning every two years is totally fine.  (I address this issue in more detail in my book Energy Audits and Improvements in Commercial Buildings.) Furthermore, an argument could be made that this cleaning can be done by building owners, it does not need to be done by a trained service technician. Servicing and inspection of fossil systems must be done by trained technicians, primarily because what is really needed is a couple combustion tests, to make sure that the combustion is clean AND to make sure that combustion products are not leaking into a building, for example through a cracked furnace heat exchanger or other path.  I think there’s no question on maintenance complexity and maintenance costs:  Heat pumps – 1, fossil – 0.

Noise: I dunno. Hard one. Oil burners sure are loud. Residential baseboard heaters used with fossil boilers sure make a lot of nuisance ticking noises as they heat up. Old fossil-fired steam systems make lots of LOUD banging noises, gosh I still remember that from when I spent time in NY City. Gas furnaces can have loud air movement noise. But so can heat pumps. And in both cases, newer fans are quieter. Heat pump indoor units (the things hanging on the wall) are generally quiet, but they are not noise-free. Heat pump compressors can be noisy, but they are generally outdoors, and are still quiet enough that they are hard to hear indoors.  I’m going to say it’s a tie:  1-1.

Building cost:  A few years back, heat pumps were much more expensive. But their costs have dropped significantly and continue to drop.  We looked at a bunch of different examples in our county. Turns out that these days air source heat pump is right in the same range as a fossil heating system. Tie.  1-1.   Important note:  I believe heat pump costs will continue to drop, and within 5 years, this will be a 1-0 advantage for heat pumps.  And that may well be the tipping point that changes everything.

Aesthetics:  If the heat pump is ducted, it looks just like a forced air furnace system. But if the heat pump is ductless, you have those indoor things hanging off the wall. And the heat pump has an outdoor unit sitting outside.  The fossil systems need venting, so the building needs a chimney or other vent penetrations.  But I have to be honest:  Heat pumps – 0, fossil – 1.  This is probably the biggest thing that is ruling out heat pumps these days, in the big decision for many building owners.

Safety:  But we covered this already under maintenance, no?  It really deserves its own discussion. The big thing here for me is that fossil systems kill people, in at least two ways, and likely more. When fossil systems malfunction, they make carbon monoxide (CO), and that kills people. I believe the statistics are about 150 people in the U.S., per year.  That’s the very reason we’re all going out and getting CO detectors if we have fossil systems. If the fossil fuel is natural gas or propane, there’s also the risk of leaks, and so explosions.  Approximately another 20 deaths per year.  Finally, I’m guessing that there are fatalities that can be associated with air pollution, and with extraction of fossil fuels from the earth. It gets complicated, because heat pumps rely on electricity, some of which also comes from the combustion of fossil fuels. But that combustion, at power plants, is likely cleaner than all those oil and gas boilers and furnaces in buildings, on average. But nobody dies from heat pumps right in buildings, whereas many people do die from poisoning and explosions.  To me, 150-200 people per year is many.  So for me there is no question:  Heat pumps – 1, fossil – 0.

Comfort:  Another tough one. Those ductless systems, with a thermostat in each room, sure provide GREAT comfort, much better than just one thermostat per building.  But heat pumps have some comfort risks.  In cold climates, at very cold outdoor temperatures, there is a risk of not providing enough heat for a few hours on the coldest days of winter, if the system is not sized correctly. And if those indoor units are not placed in a good location, cold air can drop onto people in the summer, during air conditioning, so you don’t want to put them above desks, beds, or sofas.  I give up, I’m calling this a tie:  Heat pumps – 1, fossil – 1.

Reliability:  Which has more moving parts that could fail?  A fossil furnace or boiler has 1-2 fans or a pump. Plus newer ones have electronic controls.  Heat pumps have controls that are similar in complexity, no big difference there. For bigger parts, heat pumps have a compressor, and at least two fans.  I think I convinced myself:  There are more parts that can fail in heat pumps.  Heat pumps – 0.  Fossil – 1.

What’s the final score?  I have it as 7 for heat pumps, and 5 for fossil systems. Please count yourself to make sure I got it right. Close, but heat pumps already have the edge. And as time goes by and the cost of heat pumps come down, it will be an even more clear 7-4 in favor of heat pumps.

For many people, a single factor will trump all others. For those of us who care about carbon emissions, we will always choose heat pumps and not look back. For those who put aesthetics first, or for whom old concerns about heat pump comfort are too scary, even if we argue that these comfort issues have been overcome, fossil fuels are the less risky option.

Agree with my scoring?  Shout if not.

And here’s my prediction. I’m so confident of it that I put it right in the report we just wrote for heating systems in Tompkins County.  Within 30 years, and likely far sooner, we will no longer put fossil heating systems in new buildings. The likely lower installed cost, combined with the lower carbon emissions, combined with the lower maintenance, combined with the greater safety, will all win out, especially as people see that heat pumps can be designed and installed to deliver good comfort.


2 thoughts on “The Big Building Battle of the Century: Fossil Heating versus Heat Pumps

  1. I enjoyed this discussion and pretty much agreed with all your scoring. One question I had concerns the idea that inside ASHP units shouldn’t be above a couch or desk because of cold drafts during summer air conditioning. Is that true even if the air-stream is manually set to go out horizontally and not aimed down at the couch? The cold air is going to mix downward regardless, but is a concentrated draft dependent on how vanes and fans are aimed?


    1. You can control the discomfort a little by re-aiming the vanes. But my experience has been that the cold ultimately falls, and when it does, it’s difficult to totally avoid the feeling of a draft. I have seen this in three different buildings. If you hear of people who are able to avoid it, I’d be very eager to hear. Ian


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s