Tariffs for Solar plus Heat Pump

Redlander

I will shortly be having an ASHP installed (probably Vaillant AroTherm Plus 3.5 kW) and I'm also investigating getting solar PV with a battery.

I see that Octopus offer tariffs optimised for either heat pumps (Cosy Octopus) or solar+Battery (Octopus Flux or Intelligent Octopus Flux), so I'm wondering which would be best when I've got heat pump AND solar+battery. This page https://octopus.energy/octopus-smart-tariffs/ suggests it is Flux/Intelligent Flux, but a video I saw (one of Gary Does Solar) suggested that Intelligent Flux might not be suitable in a household with a heat pump, but I don't understand why.

The reason I'd like to answer this question in advance is that Intelligent Flux only works with certain batteries (currently GivEnergy and Enphase) so I need to know whether to stipulate one of these brands to my insaller.

matt_drummer

There are other suppliers than Octopus.

Why tailor your install to them?

Redlander

matt_drummer said:

There are other suppliers than Octopus.

Why tailor your install to them?

Because I've heard from several sources that Octopus is an especially good supplier and that Intelligent Octopus Flux is an especially good tariff. I would not want to unnecessarily exclude myself from that tariff.

Even if I don't go for Octopus, it would be useful to know whether it's better to optimise the tariff for solar or for the heat pump.

QrizB

That's a complicated question, since it's going to depend on the relative amounts of import and export. Intelligent Flux pays a fair bit more for export than Flux does, and the import is generally cheaper too but you miss out on the "cheap" dips.

This question might be better asked on the "Green and Ethical" forum where most of the solar geeks hang out. you can ask the mods to move it, if you want.

https://forums.moneysavingexpert.com/categories/green-ethical-moneysaving

matt_drummer

Well then,

GivEnergy or Enphase it is.

I have GivEnergy batteries and an ac inverter and Enphase micro inverters.

I would choose Enphase all day long, great stuff.

matt_drummer

But I would never choose Intelligent Flux.

I am not comfortable giving anybody total control over my stuff.

debitcardmayhem

matt_drummer said:

But I would never choose Intelligent Flux.

I am not comfortable giving anybody total control over my stuff.

I thought you were on Intelligent Go Matt?

matt_drummer

debitcardmayhem said:

matt_drummer said:

But I would never choose Intelligent Flux.

I am not comfortable giving anybody total control over my stuff.

I thought you were on Intelligent Go Matt?

I am, that's not Intelligent Flux.

Qyburn

Flux looks pretty unappealing to me. The "cheap" import is more expensive than E7, and normal export rate is lower than "Outgoing fixed". It really hinges on how much export you reckon will fall into 1600-1900 time, and whether you can avoid import at that time.

Bear in mind that when running off battery you will still import, both because the balancing act is imperfect, and if the house load exceeds inverter rating.

Reed_Richards

I have solar panels with a battery, an ASHP and an EV.  An EV tariff works well for me because I can charge my battery in winter, heat my hot water and get the house up to daytime temperature with the ASHP at the same time as charging my EV.  The Eon Next EV tariff works particularly well for me because it extends to 7am.

I've never been convinced that Cosy Octopus was a good fit to the needs of an ASHP, certainly not my system with radiators.

Petriix

Some of the E7 options are likely better, especially if your battery is sufficiently big and powerful to run the heat pump from stored cheap rate energy. Or get an EV as well then you get access to better tariffs.

Personally I'd be charging the battery to full every night at the cheap rate (even in the sunnier months) and exporting the solar generation. If you can get the house up to temperature by the end of the cheap period, the heat pump will just be ticking over to maintain the level throughout the day. I would guess 20kWh of batteries would cover that, but you might get away with less if you have good insulation (or just accept some peak rate usage in the middle of winter). 

You need to find a supplier/tariff combo that gives you access to a decent export rate. Eon Next offer 16.5p while Octopus and EDF pay 15p currently but you need to check which import tariffs are compatible with these headline export rates.