#HeatPumps #EfficientHeating #ColdWeather
Have you ever wondered why heat pumps are still more efficient for heating in cold weather than resistive electrical heating? 🤔 In colder climates, it may seem counterintuitive that a heat pump, which uses outdoor air as a heat source, can still be more efficient than traditional resistive electrical heating. However, there are a few key factors that contribute to the continued efficiency of heat pumps in cold weather.
Let’s break it down and explore why heat pumps are the better choice for heating in cold weather.
##How Heat Pumps Work
Before we delve into why heat pumps are more efficient in cold weather, let’s first understand how they work. A heat pump operates by transferring heat from one area to another using a refrigerant. In the winter, it extracts heat from the outdoor air and transfers it inside to heat the space. Even in cold temperatures, there is still heat energy present in the outdoor air that can be captured and used for heating.
##Cold Weather Performance
Now that we have a basic understanding of how heat pumps function, let’s address the question of their efficiency in cold weather. Here are the main reasons why heat pumps remain efficient for heating in cold climates:
###1. Advanced Technology
Modern air source heat pumps are equipped with advanced technology that allows them to operate efficiently even in cold temperatures. Some heat pumps are designed to continue extracting heat from outdoor air down to temperatures as low as -13°F (-25°C). This ensures that they can still provide consistent and reliable heating in cold weather.
###2. Variable Speed Compressors
Many heat pumps are now equipped with variable speed compressors, which allow them to adjust their performance based on the heating demand. This means that the heat pump can operate at lower capacities during milder temperatures, reducing energy consumption. In colder weather, the compressor can ramp up to meet the increased heating requirements, maintaining efficiency even in extreme conditions.
###3. Supplemental Heating
In extremely cold temperatures, heat pumps may rely on supplemental heating elements to provide additional warmth. This can come in the form of electric resistance heating or gas furnaces. While this does decrease the overall efficiency of the system, it ensures that the space is adequately heated during the coldest times, making heat pumps a reliable choice for cold weather heating.
##Comparing to Resistive Electrical Heating
Now that we’ve explored why heat pumps are still efficient for heating in cold weather, let’s compare their performance to resistive electrical heating:
###1. Energy Efficiency
Heat pumps are inherently more energy-efficient than resistive electrical heating. This is because they transfer heat from one location to another, rather than generating heat through electrical resistance. As a result, they can provide the same amount of heat using significantly less energy, making them a cost-effective and environmentally friendly choice.
###2. Cost Savings
Due to their energy efficiency, heat pumps can lead to substantial cost savings compared to resistive electrical heating. Especially in colder climates, where heating demands are higher, using a heat pump can result in lower energy bills and reduced operating expenses.
###3. Environmental Impact
By reducing energy consumption, heat pumps also have a positive impact on the environment. They produce fewer greenhouse gas emissions and contribute to lower overall energy usage, making them a more sustainable heating option compared to resistive electrical heating.
In conclusion, heat pumps are still more efficient for heating in cold weather than resistive electrical heating due to their advanced technology, cold weather performance capabilities, and overall energy efficiency. Despite the challenges of cold temperatures, heat pumps continue to be a reliable and sustainable choice for heating in colder climates.
When considering an HVAC system for cold weather heating, it’s clear that heat pumps are the superior choice in terms of efficiency, cost savings, and environmental impact. Whether it’s for residential or commercial heating needs, heat pumps offer a compelling solution for maintaining comfort in colder climates. So, if you’re looking for a reliable and efficient heating system for cold weather, consider the benefits of a heat pump and make the switch for long-term savings and environmental benefits.
Creating heat takes a lot of energy, which is what resistive heating does, heat pumps don’t create energy, they’re just moving it around, air condtioners do the same thing. Even 20°F air has more heat than the fluid (normally a liquid gas) that is used to move it from outdoors to indoors.
20-30F is a very good range for heat pumps to operate. They only really struggle at closer to 0F. Nearly ever place commonly habitable only hits those temperatures at night or for short periods, meaning that heat pumps work perfectly fine.
Resistive heaters are exactly 100% efficient. All the energy they use is directly turned into heat.
Heat pumps can be more than 100% efficient, because the energy they use gets turned into heat, but they also steal some of the heat from outside and put that inside. What matters is that the heat pump can get the outside radiator below the outside air temperature. That will allow it to absorb heat from the cold air.
Consider your freezer for a moment. That does the exact same thing, it absorbs heat from the cold air inside the freezer, and dumps it into your living space.
Resistive heating is 100% efficient at converting energy into heat. Heat pumps do not make heat, they use energy to move heat from outside to the inside. It requires a lot less energy to move some heat, than to create it at these temperatures.
Cold air still has a lot of heat in it. It’s only “cold” by the standards of human comfort.
Absolute zero is around -275c (-450f). Anything above that has some heat that you can extract.
This video is extremely informative on how heat pumps work, the cost efficiency arguments, and the refrigeration cycle in general which is how basically all non-resistive heating and cooling systems work. Technically, air conditioning *is* a heat pump, just a specific kind that only moves heat one direction. You’re probably referring to a system like the guy has in this video, some kind of minisplit system that moves heat in or out.
Resistive electrical heating is 100% efficient (by definition)
But heat pumps can get you more heat than the energy you spent to get that heat becuase they are stealing heat from the outside air. As long as the air outside isn’t at absolute 0, there is heat energy in it. In reality, there is higher lower limit to how much energy we can extract, but that would be on only the most extreme cold days, and that threshold is only getting pushed lower.
It’s more efficient to pump water from a really low lake to a really high lake than creating the water from scratch.
Not a perfect analogy, but even if it’s very cold outside you are still moving heat instead of creating heat. It’s just a lot harder to move it when the differential is already so big.
Electricity is really useful for making things move. That’s why it’s a great choice for cars. But it takes a lot of electricity to create heat. That’s why things like electric ovens have their own circuit in your house. A heat pump moves heat from outside the house to inside the house in the same way and AC unit moves heat from inside to outside in the summer.
Heat pumps have limitations if you live in a place where it gets very cold. That’s when a gas furnace becomes very useful. Gas creates heat very easily and works great in a furnace, especially when it gets below 0 outside.
Others have explained the way heat pumps work, but I want to add a bit about how they work.
We found these special liquids (called refrigerant). They like to suck up heat and turn to gas. They like it so much that they can do it all the way down at -15 degrees fahrenheit.
So we take these liquids and put them where we want to take heat *from*. For an air conditioner, we take heat from inside. For a heat pump, we take heat from outside. They suck up as much heat as they can and turn to a gas.
Then we pump the gas to where to want *put* the heat. Basically reverse the above. When it gets there, we put it in a machine to *squeeeeeze* it down back into a liquid. This squeezes out the heat.
So because the refrigerant can go to below zero, it can suck up heat at any temperatures above that.
In my experience heat pumps are more economical in that you will spend less to be warm enough. However if you want to be really warm anywhere in the house with no cold spots nor any temp fluctuation caused by a furnace blower motor, you want resistance electric baseboard heaters. No they aren’t cheap to run but they (and any radiant heat) are by far the most comfortable heating system out there.
There is a limit to the heating (air source) heat pumps provide. The colder it is outside, the less heating capacity it will have.
How the heck can I plug a toaster into the wall and it spits out *heat* and I can plug a fridge into the same wall and it spits out *cold*. How do we make hot or cold from electricity alone?
Imagine you have a perfect cube of air in front of you, held captive by some hyptohetical [superhero-esque energy field](https://i.redd.it/3cnyjpgzor981.jpg). Think of it as being somewhat large, let’s say 1 meter on all sides. That volume of air will have a certain amount of *heat energy* represented by something we call *temperature*. *Temperature* is just a measure of average *heat energy* in a material. *Heat energy* can’t be created or destroyed, which is pretty cool; we can exploit that fact.
Further imagine that we **crush** that cube down to a much smaller space. Let’s say, a cubic inch. Two things happen here: one, the air will become more dense, or “higher pressure,” and two, that volume of air will be a higher temperature. Mind you, it will not have gained any heat energy- you can’t create or destroy that – but rather that same heat energy from the 1m cube is being represented over a much smaller space. Same amount of energy, more concentrated.
But here’s the thing about anything rocket hot- I don’t want to hold onto it for very long. If I were holding a white-hot cube of anything, I’d start blowing on it right away, trying to cool it off. Blowing over the surface of the small cube allows for some of my breath to carry heat energy away from the cube via convection. Again, heat energy isn’t being created or destroyed, just moved from one high concentration material (the cube) to a low concentration material (my breath).
Let’s say I’m pretty effective at cooling it off, and the 1 inch cube is basically back to the same temperature we had when we started with the 1m cube… What do you think will happen if we expand the cube back to 1 meter?
Well, it’s back to its normal pressure (yay!) Again, but boy is it sure COLD! Which makes sense, because we removed some heat energy by blowing on it when it was a 1 inch cube.
This is principally how your heat pump works, same with air conditioners, refrigerators, etc. A room-temp material (refrigerant) is compressed into a higher pressure, which makes it a higher temperature. That material is fed through a radiator to bring it back down in temperature, then *reduced in pressure* and fed through the cooling system. When the pressure is reduced, that refrigerant becomes very cold, and that cold refrigerant serves to cool the surrounding materials; sometimes the items in a refrigerator, sometimes the air of a heat pump, sometimes the engine of your car.
(Now to answer your question)
To *heat* something, the process is reversed, though it often feels less intuitive. Imagine trying to grab heat energy from the air outside when outside is well below freezing! But let’s try it anyways. You feed a refrigerant outside until it reaches ~ambient temperature. Then, through a system of copper tubes, feed that chilly refrigerant into a compressor indoors. Now compress *the ever living crap out of it*. It goes from freezing, to cold. Ok, well, crap. Keep compressing I guess?
Now it goes from cold to chilly- keep going! From chilly to cool, from cool to room temp, on to warm, and eventually, up to *hot*. Now feed that hot refrigerant through your house HVAC through one system or another (usually a radiator, to blow inside air over the hot copper tubes carrying the hot refrigerant) until the material has lost most of its heat energy. Then send it outside again to decompress. When it decompresses, it will be *much, much colder* than the air outside. Think about it: all of the heat energy it previously had was just lost into your home! Now the *extremely cold* refrigerant needs to “warm up” to outdoor temps, and it does this through a radiator blowing air over that material (usually travelling through pressurized pipes).
But all of this beckons… Why would this be more efficient than resistive heating? Well the short answer is that resistive heaters will simply *pour more heat energy* into a space. Lots of heat energy. Oceans of it. And all from your electrical panel. Heat pumps quite simply *move heat energy* from one space to another (outside to inside, for example) through the use of compressors and fans, which don’t need a lot of electricity at all. In fact, the amount of heat energy a heat pump can move given the amount of electricity they use can often be many times greater than the energy used to move it! Kinda like how ants can carry way more than their body weight, heat pumps can move mountains of heat energy for not very much electricity cost.
P.s. forgive me mixing units, I just found those measurements to fit the scenario well.
Heat pumps, like the name suggests, move (or pump) heat from one place to another. Just like water wants to flow downhill, heat wants to flow from hot to cold, and it takes a pump to move it in the other direction.
It could take a lot of energy to move the heat from the very cold outdoors to the very warm indoors, but it is still less energy than to make the heat from nothing.
And as a bonus, all the energy that you use to move the heat, in the end, becomes heat.
So you have two options, use energy to just create heat, or use energy to move some existing heat inside, and create some more heat in the process. Which sounds like the better deal?
Think of them like a reverse fridge. (For heating). And fridges can get pretty damn cold. So a heat pump can work in pretty cold conditions.
Resistive heating needs to make heat
Heat pumps just need to move heat (for example from outdoors to indoors)
And it takes much less energy to move heat that already exists than to try to make the same amount of heat.