Air Source Heat Pump v others and where to find the real economic effectiveness

[Fallowfields]

Following the Govs decision to give more time to introduce net zero. I kind of had it in my head we were to be stuck with ASHP with underfloor heating, although the installation would be hideously expensive and the usage not very much more cost effective than other heating types. 

It seems now we may not be stuck with one option given the extension and  a longer time scale to make the changes. We are quickly sliding into our pension years and im now confused as to which system (no gas available) we should employ. Is there anywhere truthful where you can compare how economic all systems are. Ive googled and thats hopeless, one says ASHP another said Electric and ive even read that oil is!!! If I ask a plumber, of course they say the systems they supply are the best. Has anyone found any honesty?

[JohnMo]

So an ASHP and electric heating both use electric. Any electric heating except heat pumps produce heat at 100% efficiency. So one kWh in, one kWh out.

 

The difference is a heat pump, takes one kWh of electricity and converts to 3 to 5 kWh.

 

You never mentioned if you are doing a conversation, renovation or new build?

[ProDave]

Remind me if this is a new build?  A house you already own? old or new?

 

In a self build new house with no mains gas I would say without a doubt UFH and ASHP.  With a new build you have one chance to get the insulation right and make the heat demand low.  Whatever system you fit, you will need UFH or radiators, so ignore that cost, that is constant regardless of heat source.

 

So it literally boils down to the cost between an ASHP and an oil or LPG gas boiler.  An ASHP is probably slightly more expensive but not a lot.

 

The running costs will be about the same at the moment.

[SteamyTea]

1 hour ago, Fallowfields said:

Is there anywhere truthful where you can compare how economic all systems are

Physics and Economics books.

[Fallowfields]

16 minutes ago, SteamyTea said:

Physics and Economics books.

 

16 minutes ago, SteamyTea said:

Physics and Economics books.

Oh Lord not my strong point!!

[Fallowfields]

1 hour ago, ProDave said:

Remind me if this is a new build?  A house you already own? old or new?

 

In a self build new house with no mains gas I would say without a doubt UFH and ASHP.  With a new build you have one chance to get the insulation right and make the heat demand low.  Whatever system you fit, you will need UFH or radiators, so ignore that cost, that is constant regardless of heat source.

 

So it literally boils down to the cost between an ASHP and an oil or LPG gas boiler.  An ASHP is probably slightly more expensive but not a lot.

 

The running costs will be about the same at the moment.

Thank You , its a new build

[Fallowfields]

2 hours ago, JohnMo said:

So an ASHP and electric heating both use electric. Any electric heating except heat pumps produce heat at 100% efficiency. So one kWh in, one kWh out.

 

The difference is a heat pump, takes one kWh of electricity and converts to 3 to 5 kWh.

 

You never mentioned if you are doing a conversation, renovation or new build?

Hi, its a new build

[ProDave]

So a new build, embrace the chance to fit a LOT of insulation, properly designed, make it air tight, fit MVHR and UFH and you will have a house that needs very little heat input.  Then a small ASHP will be all you need.  It will be cheap to run, and no oil or gas tanks to bother about and no boiler servicing.

 

While you are at it, fit some solar PV on your roof and your running costs go down even further.

[joe90]

+1 to the above, insulate, insulate, insulate (and airtight) then whatever source your heat (preferably ASHP) your running costs will me minimal.

[Gus Potter]

27 minutes ago, Fallowfields said:

Hi, its a new build

 

2 hours ago, ProDave said:

The running costs will be about the same at the moment.

 

Yes at the moment, as others often point out 1kW of electricity into an ASHP for say 3 -4 kW out.. depending on the outside air temperature but as gas is say 1/3 the cost of your electricity it ends up roughly the same.

 

@Fallowfields you have probably thought all this through but for me if you are rural then I would look at your location and altitude. For example my sister lives on the island of Tiree. Here they benefit from warm seas relatively speaking when say compared with the North sea off the East coast of Scotland or say the sea off Newcastle / Norfolk. They also get a lot of wind. The air temperature never drops that low, say -4 deg C but even then only for a short period of time due to the warm sea all round.

 

They have two ASHPs that really deliver, are economic to run.. they are delighted with them. Reports are that they never hear them having to work that hard, in other words a big drop in efficiency. But as they are rural.. well very the electricity can go off.. no heating and no hot water. The house is well insulated, pretty air tight and they have a gas hob run off bottled LPG and electric ovens. They actually find this cost efective as the hob uses not much gas although catering for a good number of people most days. They also have a wood burning stove. In other words the house has some redundancy built in.

 

Before committing to ASHP I would have a look at your location. If say Wales / North Scotland at 250 - 300m + altitude then you could experience several days where the temperature is below -10 to - 15 deg C.. and regular days when the temperature stays below zero C all day and drops further at night.. what then and what if the electricity goes off? I'm not saying don't put them in... just that your location may influence the overall performance.

 

You other option is oil fired boilers.. but I think their days are numbered (I had one in a self build out in the country and at that time it was great, oil was cheep and it ran a UF stystem over two floors of the house) in the sense that the oil is delivered by companies that don't often play fair and as demand for them drops off then probably the maintenance cost will go up and the oil price will also likely go up. Maybe in ten years time you'll get you oil delivered by an EV tanker?

 

You could maybe set up you system so it can an easily take an ASHP later, use a cheep oil boiler and tank to start with and wait for the price of ASHP's to come down? It will impact on your energy performance calcs so you may need to add more insulation ect to compensate.. but that is no bad thing.

 

Of course if you had a big plot you could have a ground source pump.. ideally a stream / burn with good all year round floor or right next to the sea so you can extract heat from that... but few of us are that lucky.

 

 

 

 

 

 

 

[IanR]

3 hours ago, Fallowfields said:

Is there anywhere truthful where you can compare how economic all systems are.

 

There isn't one answer. It depends on what you are including in you economic comparison. Just day-to-day costs? Including installation? Including maintenance? Lifetime costs?

 

As a broad fuel cost comparison per kWh:

 

Fuel		Energy price per kWh (p)		Efficiency %		Heat price per kWH (p)
Natural Gas		8.0		85		9.4
Oil		9.0		85		10.6
LPG		8.7		85		10.2
Wood Pellet		13.8		85		16.2
Coal		8.9		80		11.1
Direct Electricity		30.0		100		30.0
Low efficiency ASHP		30.0		250		12.0
High efficiency ASHP		30.0		400		7.5

 

I took the energy prices off Energy Savings Trust national average on 1st July 2023  - https://energysavingtrust.org.uk/about-us/our-data/

 

There's not much to separate Gas, Oil, LPG and ASHP (I'm ignoring coal)

 

With the benefit of a £7.5K BUS grant for the ASHP, I'd expect installation costs to be similar (assuming same heat emitters), with ASHP possibly being the cheapest.

 

If it's a forever home, maybe you should consider the ease of a replacement boiler after 2035, when FF boilers will not be available. ie. whatever you go with now should be ready for a low temperature system and at least space for a UVC, positioned close to where you would site the ASHP.

 

When it comes to the other side of the economic calculation, the amount of energy used, there you can make a much bigger difference. Building to current building regs you'd likely be in the order of 50-60kWh/m² per year energy use for your space heating. It's quite easy with some care and attention and not too much additional expense to halve that.

Edited September 21, 2023 by IanR

[SteamyTea]

1 hour ago, Fallowfields said:

1 hour ago, SteamyTea said:

Physics and Economics books.

Oh Lord not my strong point!!

Both are fairly easy, at the level needed here.

 

Think of Physics as what you already know, intuitively.

There are only 3 'units' to remember, the kilogram (kg), the metre (m) and time (s).

Just about everything comes from those 3.

So you know, from experience, that catching a small ball, gently thrown towards you is easy,  Say that ball has a velocity of 2 metres per second and a mass of 0.1 kg as you catch it (this is momentum and has the unit p, for pellere, which means push, or drive).

The momentum is p = kg.v, so p = 0.1 x 2, p = 0.2 kg.m.s^-1.

When you catch it, the equation changes to the energy equation, 1/2 mass times velocity squared, E = 1/2.kg.(m.s)², E = 0.1 x (2)², E = 0.1 x 4, E = 0.4.

Energy what is called a derived unit, the joule (J), this is important as ANY energy, be it a moving mass, electrical energy, thermal energy stored energy, gravitational energy, can me expressed in joules.  The main thing is to remember that a joule is very small, the force needed to move a mass.  This force is known as a newton (N) and is equal, in everyday life a mass (kg) x acceleration (m.s²).

As you can see, those basic units of kg, m and s, keep appearing.

As a J is a very small unit, we tend to multiply them by 1,000,000 and talk in mega joules (MJ).  An MJ is still quite small, and in the domestic setting, we talk about kilo watt hour (kWh).

The kWh is a dreadful unit and causes lots of problems, but can easily be broken down into the base International System of Units (SI).

So let's try it.

k = 1000

W = J.s^-1 (joule per second)

h = hour, which is 3,600 s.

Multiply that lot together

1000 x 1 x 3,600 = 3,600,000 J

So there are 3.6 MJ in a kWh.

 

Say you buy 2 kWh of electricity.  That will be, 1000 x 2 x 3600 = 7,200,000 J, or 7.2 MJ.

As a J is mass times acceleration, and if we assume, for simple arithmetic that we start with that ball of mass 0.1 kg, then to get to 7,200,000 we have to throw it quite fast.

E = 7,200,000 (J)

7,200,000 = 0.1 (kg) x ?² (m.s^-1) (we normally use x where I have used ? to save confusion with the multiply sign, which is normally a period, .).

Let us rearrange so that ? becomes the subject (as they say in arithmetic lessons).

7,200,000 / 0.1 = ?²

72,000,000 = ?²

72,000,000^0.5 = ?, which is 8485.28 m.s^-1, which is really fast, about 19,000 MPH.  If you are wondering how I went from ?² to 72,000,000^0.5, ^0.5 is the same a taking the square root.

 

The Economics bit is really just accountancy, if your 2 kWh of energy cost you 30p/kWh (electricity price), then that is 60p, but if 'passed though' a heat pump, you should on average, get 3 times the amount of thermal energy out, at the temperature that you want, so 6 kWh of hot water or warm air in your house.  If it is gas, and it cost 10p/kWh, you will only get, on average, about 0.9 kWh out (this does depend on the efficiency and usage of the boiler, you can get close to 1.1 kWh out on a condensing boiler).

So a heat pump would work out at 60 (p) / 6 (kWh) = 10p/kWh.

Gas 10 (p) / 0.9 (kWh) = 11.1p/kWh and 10 (p) / 1.1 (kWh) = 9.1p/kWh.

 

The real Economics bit is double guessing where the electricity and gas prices will be in a few years times, and how they are impacted by not only supply and demand (we have good historic data on that side) and government intervention (currently electricity is priced by the gas price).

If there is one thing that is certain, it is that government intervention is unreliable and inconsistent.

 

I hope that helps explain what Energy actually is, and from it you can quite easily work out the energy to heat things up, move things, change things etc.  Just think of it as a mass moving and going from moving to rest, quickly.

 

(disclaimer, it is late and I have had a busy day, and it is strange for me to work during the day and do the fun stuff on here in the evening, had 15 years of having the day free and working the evenings, so may have made an arithmetic error.)

Edited September 21, 2023 by SteamyTea

[Fallowfields]

On 21/09/2023 at 20:44, SteamyTea said:

Both are fairly easy, at the level needed here.

 

Think of Physics as what you already know, intuitively.

There are only 3 'units' to remember, the kilogram (kg), the metre (m) and time (s).

Just about everything comes from those 3.

So you know, from experience, that catching a small ball, gently thrown towards you is easy,  Say that ball has a velocity of 2 metres per second and a mass of 0.1 kg as you catch it (this is momentum and has the unit p, for pellere, which means push, or drive).

The momentum is p = kg.v, so p = 0.1 x 2, p = 0.2 kg.m.s^-1.

When you catch it, the equation changes to the energy equation, 1/2 mass times velocity squared, E = 1/2.kg.(m.s)², E = 0.1 x (2)², E = 0.1 x 4, E = 0.4.

Energy what is called a derived unit, the joule (J), this is important as ANY energy, be it a moving mass, electrical energy, thermal energy stored energy, gravitational energy, can me expressed in joules.  The main thing is to remember that a joule is very small, the force needed to move a mass.  This force is known as a newton (N) and is equal, in everyday life a mass (kg) x acceleration (m.s²).

As you can see, those basic units of kg, m and s, keep appearing.

As a J is a very small unit, we tend to multiply them by 1,000,000 and talk in mega joules (MJ).  An MJ is still quite small, and in the domestic setting, we talk about kilo watt hour (kWh).

The kWh is a dreadful unit and causes lots of problems, but can easily be broken down into the base International System of Units (SI).

So let's try it.

k = 1000

W = J.s^-1 (joule per second)

h = hour, which is 3,600 s.

Multiply that lot together

1000 x 1 x 3,600 = 3,600,000 J

So there are 3.6 MJ in a kWh.

 

Say you buy 2 kWh of electricity.  That will be, 1000 x 2 x 3600 = 7,200,000 J, or 7.2 MJ.

As a J is mass times acceleration, and if we assume, for simple arithmetic that we start with that ball of mass 0.1 kg, then to get to 7,200,000 we have to throw it quite fast.

E = 7,200,000 (J)

7,200,000 = 0.1 (kg) x ?² (m.s^-1) (we normally use x where I have used ? to save confusion with the multiply sign, which is normally a period, .).

Let us rearrange so that ? becomes the subject (as they say in arithmetic lessons).

7,200,000 / 0.1 = ?²

72,000,000 = ?²

72,000,000^0.5 = ?, which is 8485.28 m.s^-1, which is really fast, about 19,000 MPH.  If you are wondering how I went from ?² to 72,000,000^0.5, ^0.5 is the same a taking the square root.

 

The Economics bit is really just accountancy, if your 2 kWh of energy cost you 30p/kWh (electricity price), then that is 60p, but if 'passed though' a heat pump, you should on average, get 3 times the amount of thermal energy out, at the temperature that you want, so 6 kWh of hot water or warm air in your house.  If it is gas, and it cost 10p/kWh, you will only get, on average, about 0.9 kWh out (this does depend on the efficiency and usage of the boiler, you can get close to 1.1 kWh out on a condensing boiler).

So a heat pump would work out at 60 (p) / 6 (kWh) = 10p/kWh.

Gas 10 (p) / 0.9 (kWh) = 11.1p/kWh and 10 (p) / 1.1 (kWh) = 9.1p/kWh.

 

The real Economics bit is double guessing where the electricity and gas prices will be in a few years times, and how they are impacted by not only supply and demand (we have good historic data on that side) and government intervention (currently electricity is priced by the gas price).

If there is one thing that is certain, it is that government intervention is unreliable and inconsistent.

 

I hope that helps explain what Energy actually is, and from it you can quite easily work out the energy to heat things up, move things, change things etc.  Just think of it as a mass moving and going from moving to rest, quickly.

 

(disclaimer, it is late and I have had a busy day, and it is strange for me to work during the day and do the fun stuff on here in the evening, had 15 years of having the day free and working the evenings, so may have made an arithmetic error.)

I think my head just exploded 🤪 You clever clog

[Marvin]

Hi @Fallowfields

 

We have no mains gas available for our bungalow of about 100m2 floor area which we insulated to the most recent standards. 

We have a mechanical ventilation heat recovery system(MVHR), ASHP and PV on the roof. A new build is very suited to an ASHP in my opinion because of its standard of insulation and airtightness. 

We started with bottled gas and a gas boiler with radiators, and later converted to an ASHP. The real benefit with an ASHP for us is using the PV generated energy to reduce the amount of energy the ASHP uses from the grid. This you cannot do with a gas boiler. Its different to use - like the difference say between an AGA and a gas boiler, as in, you need to understand how to get the best from your system.

 

Choose your emitters (radiators or underfloor heating or what ever way to get the heat into the room) carefully.

 

Your thick insulation will slow the home becoming colder in winter and hotter in summer, but realise that solar gain is an important factor to take into consideration. In the mornings, in the summer, our east facing windows produce enough heat to heat the whole building in winter!  

 

Good luck.

 

Marvin

 

 

[Fallowfields]

On 03/11/2023 at 20:04, Marvin said:

Hi @Fallowfields

 

We have no mains gas available for our bungalow of about 100m2 floor area which we insulated to the most recent standards. 

We have a mechanical ventilation heat recovery system(MVHR), ASHP and PV on the roof. A new build is very suited to an ASHP in my opinion because of its standard of insulation and airtightness. 

We started with bottled gas and a gas boiler with radiators, and later converted to an ASHP. The real benefit with an ASHP for us is using the PV generated energy to reduce the amount of energy the ASHP uses from the grid. This you cannot do with a gas boiler. Its different to use - like the difference say between an AGA and a gas boiler, as in, you need to understand how to get the best from your system.

 

Choose your emitters (radiators or underfloor heating or what ever way to get the heat into the room) carefully.

 

Your thick insulation will slow the home becoming colder in winter and hotter in summer, but realise that solar gain is an important factor to take into consideration. In the mornings, in the summer, our east facing windows produce enough heat to heat the whole building in winter!  

 

Good luck.

 

Marvin

 

 

Good shout, yes, I will consider the windows positions and sizes to gain the best solar gain, thank you. FF

[Marvin]

7 hours ago, Fallowfields said:

Good shout, yes, I will consider the windows positions and sizes to gain the best solar gain, thank you. FF

Hi @Fallowfields   Bit confused. To be clear: our home quickly heats up (and can get way too hot unless we do something about it ) in the summer because of solar gain.

[Bozza]

New build with good insulation in the south, and no mains gas? No brainer ASHP, especially if funding is available.

 

In real terms, our recent leccy bill a few days ago for Oct was £157.  Standard obscene flexible tariff.  ASHP with no solar.  214 sqm.  House occupied 24/7 and wife WFH, and we get £93 per month grant to offset that.  Never been cold / always hot water.  No horrible fuel tank in the garden.

ASHP horror stories usually due to bad installation, badly insulated / unsuitable house, or settings errors.

 

We’re in an exposed location in NE Scotland.  It’s cold and windy here.   My neighbour is Norwegian they’ve been using ASHP for decades.  The non £££ bit is doing the right thing by the environment.  
 

ASHP isn’t the right or only solution but sounds like it would be right for your build TBH.