@jml

Hi Jordan, welcome to the forum.

You sound like you have done a lot of research already and that your house is well suited to low temperature heating.

You may already know that in terms of SCOP, if you can get to about 3.6 then you have reached parity with mains gas heating. Oil is a bit more difficult to judge because its price is so volatile, but in my opinion a well performing heat pump will beat it on a like for like basis.

The crucial point here is well performing. You should be able to get an SCOP of well above 4 with a good installation (see heat geek COP guarantee)  which will rival or beat oil. Notice that I also said like for like. That doesnt have to be true. The price of oil is set at current market rates and you cant drill for you own in your back yard. There are many heat pump/time of use tariffs that you can use to your advantage to get the average unit price of electricity lower. If you can run to it, solar panels will lower your bills too and a home battery even more so. If you intend to get an Electric vehicle in the future, then the average price you pay per unit will plummet. I think im paying about 12-15p per kWh on average.

Its also worth thinking ahead, the new government looks keen on bringing more renewables on line and its possible the stupid pricing system we have at the moment may be looked at (fingers crossed), so electricity prices could fall.

If a new oil boiler will cost you £6000 and you can get the £7500 grant then that should get you a good install with perhaps some left over.

I would get the heat loss estimate checked just to be sure as MCS can over estimate quite a bit. There are various ways you can sanity check their estimate if you dont mind a little maths. You also want to be looking for a quote with the lowest flow temperature you can get as that will increase your COP.

If you do decide to go down the heat pump route then you will find lots of help on here as to what to look for to get a good install. Vaillant make good heat pumps but they are plenty of other good makes around too.

Its worth pointing out too that your electricity bills would vary wildly over the year so you have to be prepared to take an average.

good luck!

Posted by: @jml

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Valliant will provide a decent COP/SCOP

Don't get to hung up on makes, they nearly all can provide around the same same cop in like for like conditions. It's the system they are connected to that makes the real difference in performance and how they are operated.

If changing all radiators aim for as low a flow temperature as possible, to get most benefit.

This site is one of the most comprehensive for what size heat pump you might need, as you may have read too big a pump can’t be less efficient 

https://energy-stats.uk/what-size-heat-pump/

There are several regular posters on the forum who have successfully moved from oil and might reassure you. Or search the site for ‘oil boiler’ if you get impatient.

Posted by: @judith

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This site is one of the most comprehensive for what size heat pump you might need, as you may have read too big a pump can’t be less efficient 

https://energy-stats.uk/what-size-heat-pump/

There are several regular posters on the forum who have successfully moved from oil and might reassure you. Or search the site for ‘oil boiler’ if you get impatient.

A few misleading facts in the attached.

Cylinder reheat time is from 10 degs, you will do that once, then after you are raising the cylinder 5 to 10 degs only depending on your heating strategy. My 6kW unit does a reheat twice per day currently at 30 to 40 mins at a time up to 50 degs.

No allowance seems to be made at the lowest design temperature to actually have enough over capacity in the heat pump to reheat the cylinder and to heat the house. Which is an omission.

Hi guys!

Thanks for getting back to me so quickly.

@johnmo Aye, thank you. I am not too concerned about the brands but rather thought it an idea just to inform of the system i may be getting. I understand all brands these days  offer close to what the others do. Also, thank you for info regarding hot water cylinder heating. I was worried i would have the extra cost of boosting with the immersion element but good to know it can be done via the heat pump heat process too. (I hope i am reading that right hence you 'does a reheat'.

@judith - Thanks for that. I have had a good look on Valliant and at their spec sheets.

@bontwoody I would get the heat loss estimate checked just to be sure as MCS can over estimate quite a bit. There are various ways you can sanity check their estimate if you dont mind a little maths. You also want to be looking for a quote with the lowest flow temperature you can get as that will increase your COP.

@bontwoody Thanks bontwoody! I did try doing the Math, and have tried to set myself up for worse case scenario regarding costings based on Heat Geeks W/m2 hierarchy.

Basically I started with worse off state to my current situation ie. Victorian property with no insulation, 50-75mm loft insulation, single glazed windows compared to my current house which is obviously far better insulation wise than that.

So, Victorian proeprty on heqt Geeks States 65-85 W/m2 I chose 75 W/m2

75W/m2 x my house area 93m2 = 6975W = 7Kw (as it happens I have been quoted a 7Kw heat pump)

As per H Geeks 7Kw x 1500 for heating = 10500Kwh

+

7Kw x 500 for Hot water = 3000Kwh

= Total 14000Kwh Demand

(Now my installer gave me HP combined performance of 2.91 SCOP at 45oC flow rate and a total demand of 14600kwh) 

I have pushed those boundaries further a little further and given myself a SCOP of 2.5 (not a great deal difference but I guess a worse case is better than an unrealistic expectation, and I can play further with these figures to project different potential spendings) 

So 14000Kwh Demand / 2.5 SCOP = 5600Kwh x Elec Unit 0.22p = £1232 Costings to power heat pump through the year.

(This of course could/well be reduced in the summer months with minimal/low usage, improving the SCOP and efficiency, not to mention the other hacks and tweaking of controls with weather compensation etc and given the fact I have already set my conditions to an old Vict property not my current one that is moderately well insulated.)  

Does this make sense and look right to you based on the math you are referring too??

Of course I have to factor in appliances but that is minimal given my usage of low wattage devices.

I also agree with you, this place seems amazing for all one needs to know, you are all so knowledgeable which makes things clear and understandable. 

If you or anyone has more info regarding the hot water cylinder that would be great? I fear I would need to fire the immersion element which would use more electricity (right?) and so if there are ways to override that so the heat pump heats house and water that would be great to know. 👍 

Again, I thank you in advance.

7Kw x 500 for Hot water = 3000Kwh

3500 not 3000

@bontwoody & @judith 

It seems you both have a nice system setup!

if only i had a decent solar array then this whole ASHP would be a no brainer!! 👍 

Posted by: @jml

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more info regarding the hot water cylinder that would be great?

Basically you store water between 45 and 50. I store at 50 and heat twice a day (210L) the cylinder volume is bigger than an oil system hot water cylinder as the energy storage volume is related to the stored temperature and volume. At 50 degs there is zero risk of legionella, as at 50 degs 90% plus of legionella dies in 2 hrs.

The other issue is heat transfer when heating the cylinder. You want the lowest flow temperature from the heat pump and this achieved with a large heating coil in the cylinder. The bigger the better, ideally 3m² plus.

The CoP of 2.9 is closer to what you would get at -3 and 45 flow temp. Most the time it's nearer 7 degs and your flow temp came down to 35 the CoP would be closer to 4.5, if you have an open system.

@jml

Posted by: @jml

↑

I have pushed those boundaries further a little further and given myself a SCOP of 2.5 (not a great deal difference but I guess a worse case is better than an unrealistic expectation, and I can play further with these figures to project different potential spendings) 

So 14000Kwh Demand / 2.5 SCOP = 5600Kwh x Elec Unit 0.22p = £1232 Costings to power heat pump through the year.

(This of course could/well be reduced in the summer months with minimal/low usage, improving the SCOP and efficiency, not to mention the other hacks and tweaking of controls with weather compensation etc and given the fact I have already set my conditions to an old Vict property not my current one that is moderately well insulated.)  

Does this make sense and look right to you based on the math you are referring too??

Of course I have to factor in appliances but that is minimal given my usage of low wattage devices.

I also agree with you, this place seems amazing for all one needs to know, you are all so knowledgeable which makes things clear and understandable. 

If you or anyone has more info regarding the hot water cylinder that would be great? I fear I would need to fire the immersion element which would use more electricity (right?) and so if there are ways to override that so the heat pump heats house and water that would be great to know. 👍 

Hi Jordan

So given all the insulation upgrades you have done, I think you might be being too pessimistic. Perhaps 50 W/m2 might be a better guide. Also the heat geek sheet is there to give you an idea, you should look at the methods described by Michael Podesta in the link and use any historical oil usage figures you might have to give you a more accurate guide.

The combined SCOP figure you have been given doesnt look very impressive and I would be getting other installers to have a look.Have a look on https://heatpumpmonitor.org/ to see other systems performance.

As mentioned, system design is key to getting a good SCOP and you dont want to be saddled with a system that is expensive to run. As well as low flow temperatures, you will be looking to avoid the use of buffer vessels (which some installers insist on putting in and which lower COP). It is also beneficial if the installer will use anti frost valves rather than antifreeze fluid. The latter reduces the capability of water to transfer heat.

Modern high temperature heat pumps negate the need for an immersion top up for legionella protection. Although there will still be an immersion in your tank for emergencies 🙂 The heat pump will either be set to heat the house or the water tank and not both at the same time as different flow temperatures are required. When you heat your DHW is largely a matter of personal choice. At night will have less impact on heating (and perhaps cheaper electricity), by day will have better COP as the outside temperature is usually higher.

Morning guys! Thanks so much for this. Very interesting.

@bontwoody

Here are the complete stats given to me. (see attached)

Regarding the pessimism of my calculation I thought that better to give me a worst case scenario.

I guess the problem I have is given my busy schedule I have actually been granted the funding and have a small window to accept the offer from energy savings trust based on the current quote I have been given from install. As the offers are in granted in conjunction with the quote I fear I would have to start the whole process again.

Based on quote they are fitting a 28mm anti freeze value and also a 25L CB Heating Expansion Vessel Is this the same as a additional heating chamber that should be avoided? I'm guessing this is similar to the normal expansion vessels we get on out oil boilers?

The CoP of 2.9 is closer to what you would get at -3 and 45 flow temp. Most the time it's nearer 7 degs and your flow temp came down to 35 the CoP would be closer to 4.5, if you have an open system

So based on my attached docs are these the sort of figures I would be looking at @johnmo, so only really low performance and scop in the expected colder months?

Not sure I entirely understand all the figures, so a little more help there would be great. When it says renewable 9000+ kWh I'm guessing that is what I a drawing receiving back in energy from the usage the HP is using?  

Look forward to reading your take on the above 👍🏼

Thanks guys

@jml Hi Jordan

I cant see an attachment? The expansion vessel is as you suppose normal and not a buffer vessel. Good that they propose anti frost valves and not antifreeze solution 🙂

Do you have any previous oil usage data?