Octopus Cosy - new tariff for ASHP owners

[dpmiller]

6 hours ago, Dreadnaught said:

 

Off topic. I have been reading online that shower mixers need a minimum hot-water-feed temperature of 55º to 60º to function correctly. Does keeping your tank at 48º cause your shower mixers to go haywire 😄?

Our el-cheapo mixers work perfectly well down to mid-40s.

[ProDave]

9 hours ago, Dreadnaught said:

 

Off topic. I have been reading online that shower mixers need a minimum hot-water-feed temperature of 55º to 60º to function correctly. Does keeping your tank at 48º cause your shower mixers to go haywire 😄?

Never noticed a problem.

[ReedRichards]

9 hours ago, Dreadnaught said:

 

Off topic. I have been reading online that shower mixers need a minimum hot-water-feed temperature of 55º to 60º to function correctly. Does keeping your tank at 48º cause your shower mixers to go haywire 😄?

 

I keep my tank at 50 C but the output from the tank is mixed down to a lower temperature, about 42 C I think.  This is mainly because my OH deplores water that is painfully hot.  We have three shower mixers and they all work perfectly well.  

[jack]

9 hours ago, Dreadnaught said:

Off topic. I have been reading online that shower mixers need a minimum hot-water-feed temperature of 55º to 60º to function correctly. Does keeping your tank at 48º cause your shower mixers to go haywire 😄?

 

 

Not my experience. We run our tank at 50 degrees and there's no issue at all with the mixers, even as the tank draws down and the hot water temperature drops. They're Crosswater Mike, for reference.

 

Actually, we have a cheap mixer set in the downstairs shower and it's fine too.

[Dreadnaught]

Thanks all. I wonder why the instructions for the shower mixers all say something like this then…

 

(This one selected at random from Google – for "Heritage Bathrooms".)

[Gone West]

12 minutes ago, Dreadnaught said:

I wonder why the instructions for the shower mixers all say something like this then…

I'm another one who didn't have a problem. Our tank was kept at 45C and the shower mixers worked fine as did the thermostatically controlled valve on the bath.

[ReedRichards]

I have an unvented cylinder with a pressure regulator on the rising main (and, I think, another regulator on the hot water).  So hot and cold waters are at similar pressures.  Perhaps the specified "at least 10 C above the required blend temperature" is to cope with the hot water being at a much lower pressure than the cold water?

 

Now I remember, I did once have a problem with a mixer shower when the pressure regulator on the rising main was installed and set too low.  I can't remember what went wrong but I remember the solution was to increase the cold water pressure a little. 

[Dave C]

1 hour ago, Dreadnaught said:

Thanks all. I wonder why the instructions for the shower mixers all say something like this then…

 

(This one selected at random from Google – for "Heritage Bathrooms".)

 

My mixer shower says the same, but echoing the other feedback - it works fine with the hot water coming in at 48C (or realistically a bit less, given it's only 48 when the heat pump has just finished).

 

Did have to tweak the temperature adjustment on the mixer up to its maximum, though.

[George]

Interestingly my taps are too hot to put my hand under but shower is fine. Presumably loss of heat being in spray form. Run at tank at 45C, unvented so shouldn't be issues with differential pressure. 

[RichardL]

Gut feel, I didn't run precise numbers, It feels more like a winter battery tariff (or battery without solar) so you can charge up twice a day and time shift usage a little later without needing capacity for the whole day in the battery bank?

[Dave C]

That's probably fair - I have a battery, but initially made the mistake of comparing the Cosy price to my current Octopus Go prices; of course prices have gone up since my last renewal! So you get two shots per day at charging your battery, and the price is higher than Go, but less than double.

 

Working the figures out, for my battery I reckon Cosy is cheaper than Go on days where I'd use ~20kWh or more. That's essentially never during the no-heating part of the year, but during the winter ... eh. Probably a bit of a toss up: in January, that's the majority of days for me, probably about half the time in December/February - so for those three months, it's better than Go. The other 9 months of the year (especially when there's no heating going on!) it's worse. If you were willing to switch to it just for the winter months ... yeah, it could work.

[canalsiderenovation]

We have been looking at Cosy as our Go Faster 5 hour 830pm slot expires in March (the heating is coming off when our Go Faster expires I don't care what the temperate is outside)! 🥶

 

If we move to Go we are limited on the 0030-0430 times at 12p (providing rates do not go up) and their day rate is more expensive than Cosy although I'm not clear if their day rate is reduced because of the government cap. Whilst this is good for running appliances, charging etc I am not sure if I'd want to use the dishwasher and washing machine then as there is always the risk of flooding. Also running the ASHP for heating during these times isn't particular helpful as we will be asleep, rather I'd prefer it to be warmer when we are up and it's likely we will need the heating on at non Go times even more than we do now (we boost temperatures during the Go Faster times). It's demand on the heat pump for our heating, hot water and other appliances in a 4 hour slot and as others have said trying to do the heating and hot water with th ASHP at the same time doesn't work well.

 

The current go Faster slot has also been useful as we could run appliances when we were still awake, charge up things etc and as we were still very much awake at 830pm. With the normal Go times we would have to set timers for things like laptops etc to charge during the cheap rates. 

 

As someone has said, it's the winter and likely 6 months of the year that it's the heat pump demand that's the issue as our heat pump is off 6 months of the year because our solar does our hot water and normally all our appliances and charging.  With limited solar at the moment we are running large appliances during Go Faster. As we both work from home (730-4) the Cosy would work well for us, laptops running etc and with solar the peak time would only likely be an issue ok in winter when there is no solar 4-7pm.

 

We may be looking to invest in batteries next year and if we do perhaps you could use use battery in the peak time?

 

Our heat pump is set to a minimum of 18 degrees and boosts to 20.5 degrees during Go Faster and again comes on in the morning. In the cold snap it was kicking in mid afternoon again.

 

Ps I did have the temperatures higher until someone bought me an Oodie. It changed my life 😂 

 

 

 

 

Edited December 22, 2022 by canalsiderenovation
Edit

[ProDave]

13 hours ago, canalsiderenovation said:

charge up things etc and as we were still very much awake at 830pm. With the normal Go times we would have to set timers for things like laptops etc to charge during the cheap rates. 

I doubt the cost of charging small things like that is significant.  Though I would not do it during the silly early evening rip off peak.

[PhilT]

I've registered for this as it fits my situation quite well, and today called to check as I had no email acknowledgement. Good job I did as my Cosy registration triggered an automatic process to give me a new smart meter which I already have. Now they are aware of the issue hopefully it will prevent a log jam building up of unnecessary application processes to give all cosy applicants a new smart meter, whether they have one or not. But be prepared for a wait if you do register.

[willy_eckerslyke]

Something that might change your thinking, if you have solar, is that Octopus will pay 15p/kWh for export on Cosy and only 4.1p/kWh on GO/Intelligent.  For me this makes a big difference and means that Cosy would be cheaper than GO/Intelligent even though I have an EV. - I have solar + Heat Pump + EV.

 

[canalsiderenovation]

17 minutes ago, willy_eckerslyke said:

Something that might change your thinking, if you have solar, is that Octopus will pay 15p/kWh for export on Cosy and only 4.1p/kWh on GO/Intelligent.  For me this makes a big difference and means that Cosy would be cheaper than GO/Intelligent even though I have an EV. - I have solar + Heat Pump + EV.

 

Interesting! We have never exported before - do you have to sign up for it or do anything for extra? At the moment any excess is diverted to the hot water but I know at times we would have had a excess but we have never exported before so unsure what we do. We are hoping to sign up with cosy.

Edited December 24, 2022 by canalsiderenovation

[willy_eckerslyke]

You do have to sign up for it.  All the details are on the Octopus website.

[Tim Pearson]

On 21/12/2022 at 21:07, Nick Thomas said:

Hmm. I'm trying to like this tariff, but I'm not sure I can.

 

My PV generation overlaps the 1-4pm period; that's already sufficient to run the heat pump and charge the battery, so it'd only really be useful on cloudy days. Even today, winter solstice, I got a cool 7kWh out of the panels.

 

7 Kwh That’s impressive ! What capacity is your PV set up?

[Nick Thomas]

@Tim Pearson3.6kW, it was a bright sunny day. Today I harvested ~3kWh, by contrast; I think the lowest I can register is 0.1kWh, and I've seen that on occasion.

[Ferdinand]

For anyone going for this, remember that setting up an export from Octopus puts quite heavy documentation requirements on your solar setup, and can take 4-8 weeks or more.

 

Plus any time for a Smart Meter.

 

So this may be in for spring not winter.

 

F 

[PhilT]

7 hours ago, Ferdinand said:

For anyone going for this, remember that setting up an export from Octopus puts quite heavy documentation requirements on your solar setup, and can take 4-8 weeks or more.

 

Plus any time for a Smart Meter.

 

So this may be in for spring not winter.

 

F 

Cosy is working for me now but yes I'm still waiting four weeks after install for an MCS certificate before I can export using Octopus Outgoing Fixed. Fortunately I'm able to use most of what I generate at the moment running the heat pump.

[Ferdinand]

5 hours ago, PhilT said:

Cosy is working for me now but yes I'm still waiting four weeks after install for an MCS certificate before I can export using Octopus Outgoing Fixed. Fortunately I'm able to use most of what I generate at the moment running the heat pump.

 

You will also need a letter of acknowledgement of having received the MCS Certificate from your DNO, iirc.

 

I had a thread about it somewhere, titled something around Octopus Otgoing Agile.

[PhilT]

2 hours ago, Ferdinand said:

 

You will also need a letter of acknowledgement of having received the MCS Certificate from your DNO, iirc.

 

I had a thread about it somewhere, titled something around Octopus Otgoing Agile.

That may be true for Agile but for Fixed the online application only asks for the MCS number from the certificate. My PV supplier has already done the DNO application.

[Steve W]

I have Solar PV coupled to 18.5KWh of batteries and Economy 7. At this time of year the ASHP runs between 12.30am and 8.30am (and 7.30pm to 8.30pm upstairs only) and the batteries are also charged as necessary. The average temperature is around 20C when I get up, peaks around 21.5 and falls back over the evening. My average consumption for everything is around 30KW at 14p/kw. The heat pump is showing at about 13KW with  COP of just under 3 - this includes hot water and running it at night. 

 

I'll be sticking to E7 / Solar

[SteamyTea]

4 minutes ago, Steve W said:

kw

 

4 minutes ago, Steve W said:

KW

kWh