Octopus Cosy heat pump and Intelligent Octopus GO tariff

pjaj

I already own an EV and next week Octopus are installing a Cosy heat pump.

My calculations indicate that I will be better off upgrading from GO to IOG than switching to the Cosy Octopus tariff. (your mileage may vary). Obviously I would like to take advantage of any cheap periods over and above the 6 hours from 23:30 to 05:30 every day.

Has anyone any experience of doing this? How easy is it to tell the heat pump to use the variable cheap periods? Is there any way to automate this?

Netexporter

You need to install a home battery, that you charge up on the cheap overnight rate, to run the heat pump (and the rest of the house) at a low cost throughout the day. The overnight cheap period isn't directly useful, as you normally have the heating set back at night, so the heat pump is largely inactive. Set the hot water to replenish during the overnight period, obviously.

MWT

https://forums.moneysavingexpert.com/discussion/6660793/octopus-cosy-heat-pump-and-intelligent-octopus-go-tariff

As per the other post, it isn't wise to try and just start and stop the heat-pump, better to get a suitably sized battery to bridge the gaps with Cosy, or just stick with IOG and reduce the peak use if you have a larger battery…

Reed_Richards

It's easy to tell the heat pump to use the cheap periods by setting it to be off at other times. But to compensate for these off periods you would need the heat pump to operate at higher water temperatures when it is on, which would cause it to be less efficient and so use more electricity. It might also mean that your internal temperature would fluctuate uncomfortably.

QrizB

It's easy to tell the heat pump to use the cheap periods by setting it to be off at other times

OPs problem is that, apart for the 0030 2330-0530 core hours, on IOG you don't know when your "daytime" cheap rate slots will be until they've started.

It's not something you can programme in advance.

To be (mostly) foolproof you'd need some sort of home automation system that senses when the ECV s charging and then signals the heat pump to start up.

(Edit when MWT pointed out my error. I do know this, I'm on IOG myself!)

Reed_Richards

Yes, sorry, I misread the OPs plan. But what happens on IOG if your car doesn't need charging? Do you then just get the core hours?

MWT

https://forums.moneysavingexpert.com/discussion/comment/81933031#Comment_81933031

23:30-05:30 on IOG …

Also it is not unusual to have scattered HH periods and a heat-pump really isn't designed for short bursts of activity.

I still think having even a relatively small home battery would make a lot of difference as you can recharge during the low-rate periods and then extend the time the heat-pump can be using cheaper power…

Newbie_John

I think that's where it all gets complicated.

You'd be better off knowing the actual consumption and then you can compare the actual costs. Your heat pump more or less will run for half a year and car for the entire year - so as long as you're not on the fixed tariff you can switch between them.

Cosy itself isn't that good for heat pump, as if you set 22°C at low rates, 18°C at peak rates it will affect COP meaning it will use more electricity then it would have of it was set to the same temperature all day.

So I'd probably do April till October on Go, then 6 months of winter on Cosy (mostly as it's cheaper through the day). After a year of knowing your usage numbers revisit it.

MWT

https://forums.moneysavingexpert.com/discussion/comment/81933392#Comment_81933392

So much depends on the balance between EV and heat-pump as when you move to Cosy you raise the cost for the EV charging and significantly complicate how and when you charge.

I'll stay on IOG for next winter because of the low rate I'll be getting on the IOG Feb 12 month fix that cuts in next month when my current fix expires.

It will be a crazy low rate because of the 3.5p reduction hitting 1st April, and I have a large house battery.

I'll be using some peak electricity for sure, but not enough to lift the average price close to Cosy.

… but if someone is a low-mileage driver, Cosy can make sense even though I don't consider it a good way to run a heat-pump.

Newbie_John

@MWT if you're lucky to lock in that 3.5p then it's a no brainer, but I think current version of Go is 10.5p!

But yeah, it really is that ratio - in July car will use more, in January Heat Pump.. so whatever uses more switch

Qyburn

Currently Go is showing as 10.5p and IOG 9.0p. Has it been confirmed that these April price reductions will directly be applied to Go or IOG off peak rates? I'm conscious that the opposite didn't apply, my Go stayed at 8.5p through a number of price cap increases.