Hacker News Reader

Comment by the__alchemist | Hacker News Reader

Hey - I've been following the steady stream of articles and discussion here about heat pumps, so I have a question that is tough to answer from the articles.

Is heatpump popularity regional? My understanding was that heat pumps are the technology behind residential AC, heating, and commercial HVAC. Thermodynamic 4 step cycle of a working fluid with expansion, compression etc. Every house I've lived in has had one. The cycle is reversed to cycle between heat and AC; dumping the heat to one side of the system or the other depending on need, as controlled by the thermostat.

What is the alternative? I've seen in (new and old!) England they use natural-gas radiators sometimes, and have no AC, or window AC units. Is that it, and now areas with those are switching more to heatpumps? Or is it new, more efficient heat pumps? Or do I have a misunderstanding of the existing tech?

View on HN

The houses I've been through in the Midwestern US typically have forced-air natural-gas furnaces and cooling-only non-reversible central AC. Burning natural gas is way cheaper (ignoring externalities) to generate heat than even a heat pump, and can be easily scaled up to provide tons of heat on really cold winter days. Plus, modern heat pumps are high precision, complicated, expensive tech, a furnace is old tech: just a burner and a blower.

My natural gas cost is $0.82/CCF or $0.028/kWh. Electric is $0.161/kWh. That means a heat pump needs to be 575% efficient to break even on energy cost (assuming my furnace is 100% efficient, it's not, a lot of heat goes out the chimney).

People only get heat pumps here if they're carbon-conscious.

In my area in the midwest, nearly every house has a natural gas burning forced-air furnace for the winter and a standalone air conditioner for the summer.

Newer heat pumps have gotten a lot better, and as a result a few people are starting to use them here. Even so most heat pumps are the more expensive type that rely on geothermal coils. We have extreme seasonal temperature changes that make older heat pumps impractical. For about two weeks each winter, our overnight lows are around -20F (-29C) and we often see wind chills around -40. Summer temperatures regularly reach 100F (38C).

I would venture to guess that most residential heating in the world is provided by non-heat pump sources.

In many parts of the United States, my understanding is that it would either be natural gas fired furnaces with forced air, oil fired furnaces (with forced air? not sure), radiators (with water heated by gas or oil fired furnaces), or electric resistive heating elements (e.g. baseboard heaters).

UK is almost exclusively hot water radiators heated by natural gas boilers (or oil boilers in rural areas not on the gas grid).

There is a push by government to switch to electric heat pumps driving hot water into larger, cooler radiators (as this is more efficient for the heat pumps), backed by a £7500 grant for the pump and installation (with limited take-up).

Thanks for the info on this! It sounds like my experience has been biased by coincidence. Ie, I've only lived in a house that was wired for gas once! (Northern VA). My childhood home (Also northern VA), both places in North Carolina, and Florida have all been heat-pump based, with no gas line.

My apartment in the UK was even weirder: It had something called a "Economy 10", with an electric heater (resistance?) in a concrete slab under the floors that would run at night, then release heat slowly throughout the day. (No A/C)

In the US heat pumps have only seen widespread adoption in the last decade or so and even then mostly in new construction applications. Most houses still use either window or central AC units and then some other mechanism for heating, oil or gas furnace, electric baseboard, etc.

Reply on news.ycombinator.com