Air Source Heat Pumps

Love the idea of Air Source Heat Pumps and I've checked out their use in areas way colder than here (northwest UK) But  are they really as efficient as the salesmen claim ?

If they are, why aren't we all using them instead of gas/oil boilers for heating / hot water ??

Anyone who's got one care to share their experience - before I blow £5000. 00 

Can not speak to the UK.

In the US market the reason heat pumps do not dominate the market is economic.

Using less total energy does not draw a direct line to dollars saved.

Here where I am located, due to the rate for electric and the rate for natural gas, gas is a CHEAPER choice, in other parts of the country that is not the case and in others heating oil is cheaper than the other two so lots of folks use it.

Heat pumps are named so because they transport heat, other types of units convert energy. A lot more losses exist when you convert vs transport, but that does not mean the fuel you use to transport is cheap enough to justify.

We have an air source heat pump and love it 8 - 9 months out of the year.  It is as efficient as they say. 

Natural gas is not available in our area, so most people use propane (LP).  We decided to go with all electric instead of the propane as both are expensive, but we could use the heat pump instead of buying two different units.

The only downside is that although I can use the heat pump when it's down around 17 degrees F (which is lower than commonly thought), our winter weather gets a lot colder than that.  So we burn wood in the winter and suppliment with electric space heaters.
Now they have heat pumps with a natural gas backup system for heating, which would be ideal in a lot of areas. 

The auxiliary (or emergency) heat coil on our unit doesn't perform as well as expected, it's just like a giant toaster.  Eats plenty of power, but not enough heat for our huge house.  It's cheaper for us to just heat the rooms we're using with the space heaters and burn wood.  Our unit is 5 years old, the newer ones probably perform better.

Oh, we also bought our 5 ton unit online, installed it ourselves and called the a/c guys to check it and finish the job.  Wasn't as bad as we thought it was going to be and saved a ton of money.

Thanks for the replies ................. bit confused though

Heat pumps work like a fridge - only backwards right ? take heat from the air outside and concentrate that heat and transfer to radiators / hot water tank inside.............. The big selling point is that you're only running an electric pump and a fan ( one system even runs on  solar electricity) so surely much much cheaper than using gas, however cheap gas is

If they use comparable amounts of energy to a standard heating system then whats the point ??

Oh and 17 degrees  move South !!! jeepers thats cold 

Interesting that you installed the system yourselves - tempted to try it as i don't actually have £5000 until gardening work starts up again in the spring

Roger 

RNM35 wrote:

If they use comparable amounts of energy to a standard heating system then whats the point ??


Roger 

They do not use comparable amounts of energy, they do however us comparable amounts of dollars.

Electrical conversion is 1 watt turns into 3.14 btu's of heat. When her supplemental heat strips come on, that is the results in 100% efficient conversion which it is in reality. The thing is, that heat pump can CARRY vastly more heat than that and if you use the SEER system over there then the meaning behind a "SEER 16" unit is that it transports 16 btu's per watt of electricity used so it is far far more efficient than the actual conversion.

Natural gas produces about 1100 btu's per cubic foot, it takes a LOT of energy to get it from where it is and to your home including cleaning of the gas etc. From a pure energy view, it takes more energy to deliver the gas to your house than it does electric etc.

Heat pumps are engineered to conditions and can be done so very effectively, however this often would require significant overkill for the temp range they are used in for many folks. If it is designed for a temp of 20f it will in fact be disappointing below that temp and if that is the "balance point" it is in fact not efficient any more and consumes more energy than it transports so the strip heaters come on and the pump goes off as they are more efficient.

Its like a car/truck/tractor trailer. A car is a much better choice to efficiently move you to another place, but if you need to move you and a lot of other stuff it is no longer the right choice, however if you only use that stuff rarely, it would be kind of silly and inefficient to drive a tractor trailer around town each day.

Where I live (in east central Iowa -- say about 60 miles from the Mississippi River) we don't use air source heat pumps -- ground source only.  There is way too much variance in the local air temp and humidity to make air pump worthwhile.  We also use combination heater/heat pump units for those times when it reaches -13*F (-25*C), which isn't THAT often, but often enough you have to plan for it.

We are a NW UK based designer, manufacturer and installer of heat pumps, with several installations in the area. If you would like to see the performance that we are getting please get in touch... http://www.globalenergysystems.co.uk/index.html

Here's where we bought ours:  www.alpinehomeair.com/  .  They had a DIY unit.
Great customer service and technicians available.  My husband called them a couple times with installation questions.
Our winters get in the 0 degree F range, so there aren't too many air source heat pumps in our area.  But our electric bills are lower that most around here when we're using the a/c or heater, and our house is much larger than most around here - 3500+ sq. ft.  Our summer a/c bills are proportionally much lower than what our bills were with a new energy efficient natural gas unit when we lived in town.

Professor, you are absolutly correct.  After trying the aux heat for a couple weeks, we turned the unit off.  We also installed our own radiant heat system on the cheap, but until we get the rest of the drywall up, tile floors installed, etc, we decided not to use it.  Now  we burn wood when it's too cold to use the heat pump.

Neighbors installed a water source heat pump and had many problems over a two year period.  Cost them $20K - it's doing a good job for them now, but I wonder if they'll ever recoup all the money from lower ele bills before it's time to buy a new unit.  Others in our area have used the ground source heat pump with good results until we had an extended drought and the soil pulled away from the piping.  That was remedied by getting moisture back into the soil, but we're talking 6' down.

Once again, we love our heat pump...I'm getting tired of messing with firewood, but eventually we'll get the house finished and can use the radiant heat and suppliment with wood if we want.

OK now i get it 

But for those of us in a reasonably mild climate the maths definitely stack up  All I need to do now is find one made in the UK  -not a xenophobe but seems stupid to import an "eco friendly" product from the other side of the planet  - and earn some money !!

I guess that in areas more in need of cooling than heating a mini unit would provide hot water pretty efficiently too.
Anyone linked one to an air con unit - cool the house and heat the water ??

Roger,
Another note, I had to look up when we bought our unit, and we've been using it 3-1/2 years, so not as long as I thought.  We bought the highest SEER unit they had available at the time.  From what you posted, it sounds like they continue to make them more efficient.
A solar unit?  Wow...bet that one isn't cheap.

We have been able to use our heat pump more this winter than the previous years, but of course, not the heat strip.  I'd buy another one as long as we have the means for supplimental heat during the coldest spells. 

Sounds like your winters aren't too cold?  I bet you'd like it, too.

An air-source heat pump can provide efficient heating and cooling for your home, especially if you live in a warm climate. When properly installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes.

Roger Merry wrote:Love the idea of Air Source Heat Pumps and I've checked out their use in areas way colder than here (northwest UK) But  are they really as efficient as the salesmen claim ?

If they are, why aren't we all using them instead of gas/oil boilers for heating / hot water ??

Anyone who's got one care to share their experience - before I blow £5000. 00 

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Regards,

Ivan

WOuld love an update on the status of air-source heat pumps from a permaculture point of view.  At a recent talk in my town, and in lots of neighborhood conversations, they are touted as the way to get to net zero.  

I have some questions.

Is the total embodied energy in creating, essentially, a second refrigerator for every household in a cold climate region of the world more than remaining CO2 budget between now and 2050 can afford?
Is the risk of HCFC's--production, containment--ecologically problematic?

How does this compare to creating a rocket mass heater as far as total embodied plus lifetime use CO2 emissions, assuming that it's powered by a photovoltaic when the sun is shining?
assuming it is powered by battery when not?  (the embodied energy of the photovoltaic and the battery both need to be included in the answer to this question).

Thanks for any data or thoughts anyone cares to share.