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octopus thread .. what we use extra we pay that month currently at £150 a month dd .. all our appliance items are aa+
Soldato
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I'm considering an ASHP with Octopus. Quote was for £500 that I would have to pay, but that can change based on survey. Boiler is around 12/13 years old but unsure at this stage as it would, from what I've read, cost more to run as it's electric and not gas. Also never owned a house that has a water tank to store hot water. I'm guessing that the heat pump would run when it's cheaper rates to heat the water but what then about central heating, how does that work? Are there any calculations to work out possible cost of one against combi boiler especially over winter when it'll be on more.
The idea with heat pumps is that you keep your home space heated to perhaps a slightly lower temperature than a gas boiler central heating system might initially target, dialing in the hysteresis to keep the temp floating nicely. Tap and shower/bath hot water is handled separately.
Sometimes it's necessary to replace the radiators (and less often, some pipework) with high temperature, larger capacity units. The thermal inertia keeps the rooms at a more constant temperature; it will not heat up as quickly as a gas system. For instant hot water, you either have a hot water cylinder with immersion heater to keep it at the necessary temperature to kill legionella (>60 celsius), or a hybrid system with the ASHP for space heating and a small boiler for instant hot water.
There may be hidden costs past the initial quotation depending on the age of your system, worth getting a more detailed quote instead of a desk estimate. Insulation may be a significant extra cost depending on house age and construction.
Sometimes it's necessary to replace the radiators (and less often, some pipework) with high temperature, larger capacity units. The thermal inertia keeps the rooms at a more constant temperature; it will not heat up as quickly as a gas system. For instant hot water, you either have a hot water cylinder with immersion heater to keep it at the necessary temperature to kill legionella (>60 celsius), or a hybrid system with the ASHP for space heating and a small boiler for instant hot water.
There may be hidden costs past the initial quotation depending on the age of your system, worth getting a more detailed quote instead of a desk estimate. Insulation may be a significant extra cost depending on house age and construction.
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They still use power.
A+ on the old ratings? I think that's only D or E now. They revised them as 90% of appliances were a+.
Soldato
Octopus have given me 3 bills for September. 
(31st Aug to 22nd Sep, 23rd to 27th Sep & 28th to 29th Sep)
Why can't they just send me 1 bill covering the whole month.
(31st Aug to 22nd Sep, 23rd to 27th Sep & 28th to 29th Sep)
Why can't they just send me 1 bill covering the whole month.
Soldato
1st world problems heyOctopus have given me 3 bills for September.
(31st Aug to 22nd Sep, 23rd to 27th Sep & 28th to 29th Sep)
Why can't they just send me 1 bill covering the whole month.
Did mine in a spread sheet. Easy to do if you know how much gas you use in KWH.
Turned out to be cheaper to stick with gas for now. If electric becomes cheaper then things might change.
Soldato
Octopus have a special (maybe 2) tariffs for heat pump users
Lookup Octopus Cosy (the other one is maybe (Octopus Intelligent Cosy)
They seem to recommend 28mm piping around your home to improve efficiency, which for many folks would require major work, especially if you have for example solid floors with the pipes in them.
Octopus are supposedly releasing a heat pump solution which is uber efficient, keeps water temps hotter (so less requirement for bigger radiators) and isn't as fussy about bigger (say 28mm) plumbing.
Now that all sounds too good to be true for me, especially when anything less than a COP of about 3 for a heat pump risks it being no cheaper to run than a good traditional gas boiler. And I suspect most heat pumps fitted in regular UK homes, over a UK winter, risk being less than that (COP 3) surely?
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Soldato
Had that happen with our electric meter (Shell Energy), only found out it had stopped working at the end of our contract when i went to see what new prices were available and found a message they were bumping our DD from £70/month to £340/month.
Rang them and they told us that our meter hadn't been reporting correctly for around 8 months and it had just started transmitting and now our bill had been corrected.
My fault for not double checking the bill pdfs when they were available, i just assumed "smart meter" and they would contact me if there was anything wrong. Even had a guy come and do a manual meter reading during the time the meter wasn't transmitting and nothing flagged up on our account.
Put an extra £1100 on our outstanding bill when we were expecting to be moving to a better tariff, yay!
The size of the pipework is entirely dependent on the heat load and the SCOP you are aiming for. There is not fixed answer here and you can achieve good SCOP with narrower pipes if your heat load is lower.
You shouldn’t be accepting anything less than a SCOP of 3, that is easily achievable even with flow temps as high as 50C. Over 4 is achievable in the U.K. with lower flow temps. Anything less than 3 is a badly designed install and you should be asking for your money back.
edit: there is a whole dedicated thread on this elsewhere, I’d suggest taking this discussion there.
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Ignoring household insulation and plumbing etc, COP between summer and winter alters dramatically. ie: Your SCOP figuire. It's not unexpected over cold spells - just when you need the heating on the most - for COP to fall well below 3, and in freezing conditions we're talking potentially around 2.
Given electricy is 3-4 times the price of gas, over a cold winter we could easily imagine gas boilers being cheaper to run.
Overall, ss I type this my unit costs are, Elec:15.55 and Gas: 4.45. So I'd need a heat pump to have an SCOP of 3.88 to just cost the same as an efficient gas boiler. And I'd suggest for an avg UK house, retrofitted with a heat pump solution, when it's in use hardest in winter, that's optimistic. And if you have to go through significant plumbing/radiator upgrades/turmoil too?
I can envisage if you're building from scratch then heat pumps (ground sources?) make a good option. But for many existing homes retro-fitting seems a highly questionable choice IMHO.
ANYWAY, I'm looking forward to seeing how this new Octopus Energy Heat Pump performs given their claims about it.
EDIT for your EDIT: If you have a link that would be appreciated
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Ignoring household insulation and plumbing etc, COP between summer and winter alters dramatically. ie: Your SCOP figuire. It's not unexpected over cold spells - just when you need the heating on the most - for COP to fall well below 3, and in freezing conditions we're talking potentially around 2.
Given electricy is 3-4 times the price of gas, over a cold winter we could easily imagine gas boilers being cheaper to run.
Overall, ss I type this my unit costs are, Elec:15.55 and Gas: 4.45. So I'd need a heat pump to have an SCOP of 3.88 to just cost the same as an efficient gas boiler. And I'd suggest for an avg UK house, retrofitted with a heat pump solution, when it's in use hardest in winter, that's optimistic. And if you have to go through significant plumbing/radiator upgrades/turmoil too?
I can envisage if you're building from scratch then heat pumps (ground sources?) make a good option. But for many existing homes retro-fitting seems a highly questionable choice IMHO.
ANYWAY, I'm looking forward to seeing how this new Octopus Energy Heat Pump performs given their claims about it.
EDIT for your EDIT: If you have a link that would be appreciated
SCOP stand for Seasonal coefficient of performance. The seasonal part is really important as means the average COP over a year, which factors in the winter when it’s colder and when you use the most heat. As I said SCOP should be above 3 as a minimum, a really good retrofit will be around 4, from scratch install should be above 4.
With your calculations you need to take into account that your gas boiler is also not 100% efficient. You’ll be lucky if it’s above 90%, most are in in the low 80s%. Don’t confuse rated efficiency for actual efficiency, like cars, they’ll only get that number in absolute ideal conditions which means bigger radiators, lower flow temperatures, full weather compensation and a hot water cylinder.
Very few actually are installed in a way that can get those sorts of numbers, most are grossly oversized for heating, have too small radiators and can’t modulate down low enough for the actual heat load so they cycle which chunders through gas like no tomorrow.
This is much like heat pumps being able to achieve a SCOP of 5+ in ideal conditions, reality is more like 3-4 in a regular retrofit.
Edit: the insulation thing is a bit of a myth, it reduces running costs but it’s not a requirement to have a house with modern standards of insulation. The bigger the heat loss, the bigger the heating system. As long as heat in, is greater than heat out, the house will be warm regardless of the heat source.
The 21 page thread is in home and garden, it’s pretty active.
Heat Pumps: anyone have one/thought about it?
Right, so our boiler has decided to go to the scrap heap in the sky which has us in a rather large dilema. A replacement boiler is going to be around 3k (oh joy) or the alternative is go absolutely mad, get an air source heat pump and solar/battery array installed and hope for a payback of less...
forums.overclockers.co.uk
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Literally my very first sentence explains COP vs SCOP so I'm assuming you simply didn't read it? - "COP between summer and winter alters dramatically. ie: Your SCOP figure."SCOP stand for Seasonal coefficient of performance. The seasonal part is really important as means the average COP over a year, which factors in the winter when it’s colder and when you use the most heat. As I said SCOP should be above 3 as a minimum, a really good retrofit will be around 4, from scratch install should be above 4.
With your calculations you need to take into account that your gas boiler is also not 100% efficient. You’ll be lucky if it’s above 90%, most are in in the low 80s%. Don’t confuse rated efficiency for actual efficiency, like cars, they’ll only get that number in absolute ideal conditions which means bigger radiators, lower flow temperatures, full weather compensation and a hot water cylinder.
Very few actually are installed in a way that can get those sorts of numbers, most are grossly oversized for heating, have too small radiators and can’t modulate down low enough for the actual heat load so they cycle which chunders through gas like no tomorrow.
This is much like heat pumps being able to achieve a SCOP of 5+ in ideal conditions, reality is more like 3-4 in a regular retrofit.
Edit: the insulation thing is a bit of a myth, it reduces running costs but it’s not a requirement to have a house with modern standards of insulation. The bigger the heat loss, the bigger the heating system. As long as heat in, is greater than heat out, the house will be warm regardless of the heat source.
The 21 page thread is in home and garden, it’s pretty active.
Heat Pumps: anyone have one/thought about it?
Right, so our boiler has decided to go to the scrap heap in the sky which has us in a rather large dilema. A replacement boiler is going to be around 3k (oh joy) or the alternative is go absolutely mad, get an air source heat pump and solar/battery array installed and hope for a payback of less...
Yes, "calculations you need to take into account that your gas boiler is also not 100% efficient. You’ll be lucky if it’s above 90%" - My calculation assume a 0.9 and take that into account.
The biggest thing people seem to overlook is that elec is around 3.5x times the price of gas, which is a obviously huge amount of any proposed heat pump SCOP advantage instantly gone. ie: Over 3x of it straight away.
Thanks for the link...
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No one’s overlooking it, have a look in the heat pump thread. The heat pump will be marginally cheaper per year than a gas boiler, but that’s it. The £7.5k time limited grant makes it a no brainer to install for a lot of people that need a new boiler.
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yeah but it's not going to be 2-3x cheaper for quiet a while .. gas is not going up anytime soon ...
Soldato
Literally my very first sentence explains COP vs SCOP so I'm assuming you simply didn't read it? - "COP between summer and winter alters dramatically. ie: Your SCOP figure."
Yes, "calculations you need to take into account that your gas boiler is also not 100% efficient. You’ll be lucky if it’s above 90%" - My calculation assume a 0.9 and take that into account.
The biggest thing people seem to overlook is that elec is around 3.5x times the price of gas, which is a obviously huge amount of any proposed heat pump SCOP advantage instantly gone. ie: Over 3x of it straight away.
Thanks for the link...
From what I saw somewhere but cannot find it quickly now
Mid summer season will be the worst Cop surprisingly. Since the only real use is water at the top end of the output temp and hence the efficiency suffers.
The spring and autumn seasons the COP is highest due to the combination of some heating and water with the more ideal outside temps
Mid winter drops down some but its better than summer as whilst the conditions are less optimum, the balance being mainly heating has less impact of efficiency than in summer.
Anyway I don't think anyone is suggesting moving away from functioning gas boilers to heat pumps.
But right now the equation is that on a change being needed its pretty negligible in regards the cost benefit of either direction. For people with a suitable property.
If you have some solar and some batteries there is probably a case for heat pumps being potentially at times better than gas.
You would need to play with some numbers in regards whether an ROI would make sense in taking in cheap elec units for use later, above where you already have some capacity.
I pay 9p for units from 0:30-4:30am. I would for a bare minimum do my water heating at that time if I had a heat pump.
As someone with a modern pressurised water system I know how little the temp loss is so that window would be perfect for heating your water up, and having a tank full of hot water for the day.
The main problem is that you would need to not be on a tariff such as Cosy for that to happen and that means you would miss out on the cheaper day units.
IMO the first thing they need to do is take the green levies off elec and stick them on gas, oil, wood fuel etc. That would help level the playing field quite quickly, along with breaking the link between elec pricing and gas pricing.
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