I've been in discussion with a few people today on this one. 75degC max LWT seems to fly in the face of perceived wisdom and best practise of lowest possible maximum LWT for highest SCOP. There's only so much enthalpy in the ambient air, and to raise LWT higher requires more input energy to the compressor and more work done by the compressor. HT heat pump for DHW? Yes, absolutely. No need for immersion for Legionella cycle if you can supply DHW at 65degC to charge a cylinder up to 60degC. I do fear whether this is a [forgive the crude phrase] "pile 'em high and sell 'em cheap" pitch by Octopus. Installation cost is a barrier to roll out of ASHP, but an even bigger and unwelcome (sometimes unwitting) barrier is an unaffordable to run heating system. However efficient the Cosy 6 unit is, it'll be consuming a lot more electricity to generate water at 75degC than 55degC, and at current average energy prices be more expensive to run than a gas boiler. Octopus may have special tariffs for the product, but they are not immune to wholesale energy cost volatility, and won't be in the market to subsidise operating costs.

How many houses would HAVE to have a 75degC LWT to effectively heat the house though? Also, just because you can run it HT it doesn’t mean it has to- nothing to stop rad upgrades piecemeal down the line if the customer can’t afford the upfront cost. I’m absolutely with you on the efficiency front- I made sure mine was designed for a LWT of 35degC but not all will be able to do that and this at least gives customers the choice (and hopefully some economies of scale).

I think this is a really significant and positive development so well done to Octopus.  It doesn't really matter if 75 deg is never used in practice.  The point is that it can be claimed to be a true retrofit boiler replacement, it looks different (even if it looks like a rubbish bin to me) and it's cheap.  Real installations may end up being somewhere between a drop-in and and rip everything out-and-start-again but that doesn't matter.  With a bit of clever marketing this could be a big step forward if not a game-changer.  And if the Cosy pods/automation means we can all stop obsessing about weather compensation, delta Ts and flow rates, even better 😀 

@kev-m

What's wrong with you Kev, you can't beat a 'good dose of obsessing' to annoy the Wife. 😜 

I am looking forward to seeing the full details concerning Cosy 6.

It’ll be a RED designed heat pump, so the tech will be solid… not sure about the “room sensors that help to ensure that every room in the home is heated to the desired temperature” but it’ll be interesting to see what the final proposition is from a tech/tariff perspective.

Posted by: @chickenbig

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Octopus Energy unveils new smart heat system ‘Cosy Octopus’ at Energy Tech Summit

Sounds interesting, even if specs are TBD.

“The combination of a high-temperature heat pump (as hot as a gas boiler), Octopus smart tariffs and room sensors across your home doesn’t just open up cheaper clean heating - but more comfort too.”

Interesting to see this going against the slow-and-steady running philosophy.

Gas boilers can be run at up to 80°c but that doesn’t mean one has to run the heating at that temperature. The Cosy 6 may well reduce the COP when run at a high temperature but it also doesn’t have to be run that way. When the weather is really cold outside one might as I do, run the boiler at near 80° however normally I’d run it at 50° and boost the water temp one a week. I feel it’s better to have the ability to run the system at 80° even if it’s rarely used. Then as someone else said gradually as one can afford it upgrade the radiators to T50 or even T30. 

The Cosy 6 now has MCS certification, so you can see the SCOP figures, which seem pretty poor. Certification number HP0255/03.

Interestingly, the SCOP figures go up to 65 degrees (with a SCOP of 2.72). Presumably, this indicates that Octopus plan to design high temperature systems, at least in some cases.

@ivanopinion 2.72 is enough to beat gas on running costs, with a bit of sensible tariff selection. And that’s all that matters….

chasing high scop is great but most people just want something that costs the same as a combo swap and doesn’t cost any more than they were paying before. Tackle that and it’s an easy sell.

@HughF I agree that Octopus are probably just aiming to achieve parity with gas running costs, though I think to do this they are going to need SCOPs at least a little higher than 2.72.

Based on current price cap, gas is 6.04p, so assuming a 90% efficient gas boiler it equates to 6.7p per kWh of heat. Electric is 24.5p, so with a SCOP of 2.72 each kWh of heat is 9p. You really need the SCOP to be around 3.5. 

I appreciate that you referred to sensible tariff selection. Octopus would presumably compare with their Cosy tariff. This would bring down the price, assuming you turn off the ASHP from 4-7pm (which would impair the SCOP a little, but lets ignore that). 6 hours at 12.4p and 15 hours at 25.2p would average at 21.5p, which would mean each kWh of heat is 7.9p, so still not at parity with gas.

There are cheaper tariffs, of course, for both gas and electric. Octopus Tracker electric has averaged 18.4p over the last 3 months, so at that rate, with a SCOP of 2.72 each kWh of heat costs 6.9p. Still doesn't beat the price cap for gas. And a fairer comparison would be Octopus Tracker for gas, which has averaged 4.04p per kWh over the same period, so assuming a 90% efficient gas boiler it equates to 4.5p per kWh of heat.

To have an equivalent cost to Tracker gas, a heat pump with a SCOP of 2.72 would need to have an average cost per kWh of electric of 12.2p. I would think that the only tariff that could even theoretically achieve an average price that low is Octopus Agile. To achieve that you'd need to be using no electric from 4-7pm. 

I reckon that in order to claim parity on running costs, Octopus need SCOPs of 3.5.

(Of course, if they factor in the savings on gas standing charge, assuming the ASHP allows the customer to disconnect gas, then 2.72 might be enough for parity.)

@ivanopinion I too was disappointed to see the comparatively low SCOP of 2.72; I would have expected the Octopus team to have come up with at least 3.5 on any design they were going to put their name on. I am on Agile and would think that with a SCOP of 2.72, the only way I could be confident of even matching the gas cost would require some storage capability so as to avoid the higher rate HH’s on Agile influencing the cost. Regards, Toodles.