Heat Pumps BTU Production Inquiry

..."The main difference between a heat pump and a resistance heater is simple. An air source heat pump transfers heat, while a resistance heater creates heat. The reason that heat pumps are more efficient? Transferring heat is more energy efficient than creating heat."...

https://kobiecomplete.com/blog/3-reasons-why-a-heat-pump-is-the-best-heating-system-for-your-florida-home/

Of course there are other factors to consider, with a heat pump you need a second stage heat that's usually electric because the heat pump doesn't really cut it below freezing temperatures outside...and the heat pumps are more expensive initially...but if you go outside and check the amp draw on your compressor vs a 10kw heatstrip, you can see right away that the compressor draws considerably less amperage...probably less than half...

But which uses the most fuel? The furnace or the heat pump?

The furnace will use more fuel typically. The furnace burns fuel. The heat pump uses electricity typically.

Doesn't the electricity come from fuel?

Not necessarily...Reducing the heat load is more important than heating type anyway...

It's not the heat load. It's the total amount of fuel required to heat by heat pump or furnace with the same amount of heat to warm the same area.

Yeah I get what you're saying, but what I'm saying is that the most efficient means of heating a house is to reduce the heat load, that has the potential to save more money no matter what type of fuel you are using to heat the house...Insulate to save money...

No matter how much or efficient the insulation is, it's still going to need to be heated. So, which uses the less total fuel, heat pump or furnace for the same amount of space to be heated?

https://www.homeadvisor.com/r/heat-pump-vs-furnace/

All of that is just plain wrong.

<...It seems like the heat pump is a perpetual motion machine....>

That's nonsense.

Well if you have access to free wood, then a fireplace is the cheapest way to go...though it's not distributed evenly throughout the house...

https://www.woodheat.org/cord-wood.html

Solar heat.

A 10kw heat strip produces about 30,000 BTU.

A 30,00 BTU heat pump requires only about 10KW to move the same amount of heat from outside to inside as the heat strip does to produce the heat.

There are heat pumps that are designed to operate at lower temperatures,and the ground source slinky-coil type,buried in trenches, actually capture the latent heat when the soil freezes,so freezing soil is more efficient than 32F degree soil.

When all is said and done,the electricity required to run the heat pump is less than the electricity required to generate the heat on site.

Consider this for instance: A 10kw(30,000 BTU) heat strip consumes approximately 45.5 amps at 220 volts.

A heat pump moving the same number of BTU's will require approximately 13.6 amps.

It does not matter how the required KW are generated,the delivery cost to the end user is the same.

The heat pump requires less demand from the power plant, no matter the type;solar,wind,nuclear,etc.

..."Heat Pump systems operate on electricity and are ideal for homes in moderate climates. ... In most areas, electricity rates are lower than natural gas, meaning that a heat pump system will cost less to operate than a gas fired furnace. *Quietness. Hot air heat pumps do not make as much noise as a furnace."...

http://www.airmasterheatingandair.com/what-are-the-pros-and-cons-of-a-heat-pump-vs-a-gas-furnace.html

Air source heat pumps are capable of heating a house, even when the air temperature is down to -20°C, when they are designed for those temperatures.

The COP is much better when the air is warmer, but it can still be more efficient than electric resistance heating, typically 1.2.

In Sweden, most houses are heated by heat pumps, the majority are air source. The costs of getting a borehole drilled to 150+ metres down can outweigh the benefit of higher COP during the winter months.

A ground source heat pump can achieve a COP of 3-4 all year, while an air source heat pump will manage 3-4 in mild weather (10°C+) and as little as 1.2 in the coldest conditions.

Most in the European market have resistance heating as a booster for the few days a year that the heat pump may not cope. It is usually more efficient to select a heat pump to suit normal winter conditions and have a booster for extreme weather.

Think of a heat pump as a big refrigerator that you can run normally in the summer and backwards in the winter. When you compress a gas or liquid it gets hotter. When you expand a liquid or gas it gets colder. Just as water always seeks a to balance it's level with all the other water around it, anything hotter than its surroundings cools down and anything colder than it's surroundings heats up. So in a refrigerator you compress a liquid on the outside, the heat this makes is lost to the air surrounding the fridge. Then you pump the compressed liquid to the inside and allow it to expand. It goes colder and in an attempt to balance it's temperature to the surroundings it sucks heat out of the air/food inside the fridge. The liquid goes round in a continuous loop with some of it always being compressed and losing heat to the outside and some of it always expanding and sucking heat from the inside. You can run the thing backwards so that the liquid expands and sucks in heat on the outside and compresses so loses heat to the inside. The amount of energy needed pump the liquid around the loop and compress it is less than the amount you would need to burn in fuel to get the same heating effect inside your house, mainly because furnaces are inefficient and a lot of the heat they generate goes up the flue with the waste gasses. My home furnace has a flue made up of two concentric pipes. The air into the furnace is sucked down the outer pipe and recovers some of the waste heat going up the inner pipe with the exhaust gasses. The intake air arrives at the furnace already partially heated so I use less gas to get it up to the temperature I want it to be.

My take is a bit less complicated to understand; Recall that we are talking about a Heat PUMP, the machine literally moves heat from place to place, it does not generate the heat it is moving. Just like a pump moving gasoline from a tank to a car, a heat pump moves energy from a source to a user. The energy of the gasoline being pumped is not created by the pump. In this analogy the COP of the gasoline pump would be the electrical energy input to the gasoline pump as a fraction of the total energy embodied in the gasoline delivered.

There seems to be some confusion about the heat pump. The heat pump that I am referring to is the compressor type. Basically, the exhaust from an air conditioner. The geothermal heat pump is completely different and I'm not referring to it. What I want to know is how many btus or calories that it takes to produce a btu or calorie of heat out of the heat pump. The btu heats the water to steam, steam drives the turbine that drives the generator that makes the electrical power. It is sent to the heat pump to drive the compressor and fan. During all these processes, the amount of that btu gets smaller and smaller. It will be very small by the time it gets to the heat pump compressor. How many btus does it take to get a btu out of the heat pump starting from the boiler furnace?

I want it from the boiler.

They both are using the same electricity....but it is probably cheaper on an energy cost level, to deliver gas per therm than the electrical equivalent...so they probably come out about the same...

https://www.centerpointenergy.com/en-us/Services/Pages/natural-gas-electricity-cost-comparison.aspx?sa=mn&au=bus

The gas costs half as much, but you use twice as much, itsa wash....I prefer electric heat strips because they are simple, low maintenance, easy to fix when something goes wrong...KISS

Reread post #11.

efficiency effectiveness

Dear JMueller,

Thanks for the update. I will take your efficiency numbers as correct even though I suspect they may be from the furnace makers......

I think Papadoc was looking for the overall picture and this is pretty clear from your reply.

https://opentextbc.ca/physicstestbook2/chapter/applications-of-thermodynamics-heat-pumps-and-refrigerators/

IF you could develop a process to convert the heat directly to electricity at a very high efficiency,you could have a perpetual motion machine,which would violate the basic laws of physics.But then again,laws are meant to be broken....

If you used a condensing type boiler that uses the latent heat from the water vapor that goes out the exhaust for your heat the total carbon footprint of the heat would be reduced,disregarding cost.

Many years ago Lennox had a pulse combustion boiler that exploded the gas in a chamber and used a PVC exhaust pipe.It was over 90% efficient.

This was the same method that the German "Buzz bombers" V2 rockets used.

The opening and closing of the air valve and combustion created a buzz that could be heard from a long distance.

Older style boilers used small chunks of coal on a ember bed to produce steam for the generators.

Now,the coal is crushed into a fine powder,and burns more efficiently.

Fossil fuel generating stations are getting more and more efficient all the time,and there is an economy of scale involved;large boilers are more efficient.

Solar energy is being added to the grid at a furious rate and it will continue to be a supplement to the other sources of energy.Solar cell efficiency is also being improved constantly.

IF you are sourcing your electricity from the same place,it is more efficient for the energy provider to send less watts(Amps X Volts) to your house,regardless of what you are using them for.

There are heat pumps that use gas as an auxiliary heat source instead of heat strips,but you will still generate a bigger carbon footprint than using a heat pump.

I presume you are really interested in the lowest carbon footprint of the energy?

If an AC was installed in a wall that separates two rooms of equal dimensions and insulation with no additional air in and no air out and the AC is turned on and the ambient temperature of both rooms is 90 degrees F, what temperature would each room reach before stabilizing? What if the ambient temperature of both rooms is 40 degrees F?

Given enough time,the rooms will reach equilibrium at a higher temperature than 90F.,and continue to rise until the temperature reaches a higher temperature than the hot gas,higher because system inefficiencies add to the heat.

There isn't enough information to answer the question.

Size of the rooms, size of the Air conditioner. how well insulated etc

Obviously one room will become hotter and one room colder.

The total thermal energy input to the two rooms combined will be roughly 3400 BTUs per kWh of electricity consumed.

“The U. S. Department of Energy states that heat pumps can produce 1.5 to 3 times more heat energy than the electrical energy it consumes”

The problem with this statement is the word "produce". Air source heat pumps do not produce "heat energy" or thermal energy. They simply take heat from the outside air and move it inside.

If an heat pump is putting out 2 times more thermal energy than it is consuming in electrical energy, It just means it is taking the extra energy from the heat in the outside air.

That energy happens to be free and readily available in climates like Texas. There is no magic here, no smoke and mirrors, and no perpetual motion machine.

...that being said the cost of ownership should be mentioned...heat pumps are complicated, expensive, a pain in the arse to troubleshoot and repair...and any furnace worth it's salt will outlast any heat pump, require less repairs, are easy to troubleshoot, and usually somewhat easy to repair, though it can be expensive at times...Electric heat strips rarely fail and last a long time, are easy to repair, easy to troubleshoot...Gas furnaces supply hotter air than heat pumps, electric resistance heat supplies hotter air than heat pumps, but not as hot as a furnace...Up north I would go with a furnace, in the mid region, say Carolina's, Georgia, I would go with a 2-stage heat pump...and in the south, electric resistance heat....

Heat pumps, ground fed, replace running power costs with initial installment costs.

Kilometers of tubing must be buried 2 meters deep to provide a stable heat sink/source of approximately 12 degrees C.

A water bearing substance is pumped through the tubing and fed to heat exchangers in the dwelling. The water is now at 12 degrees C

A simple cooling arrangement, with potentially greater than a 4 energy index, pumps the water through a radiator in the dwelling that is inserted into a forced air ducting system.

The electricity is used to pump the water through the tubing and move the air through the radiator only.

This discussion is about AC heat pumps-not geothermal heat pumps. Geothermal pumps are completely different.