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EV+ Heat Pump Tarriff

 
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Electricity, Tariffs, Monitoring, Electrics & Providers
Last Post by Batpred 3 months ago
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 ChandyKris
(@chandykris)
Reputable Member Member
Joined: 2 years ago
Posts: 207
06/06/2026 11:55 am  

@etchedpixels Absolutely, the 4 pm to 7 pm penalty could make a difference, especially if the house is all electric and use electricity for cooking. Until recently, I didn't even realise that Octopus offers an Eco7 electricity tariff. With that tariff, it's 1.5p cheaper than Cosy during off peak, albeit it's only 7 hours and they are all in a single slot unlike Cosy. Plus there's no penalty during the evening peak slot and the day rate is about 2.5p cheaper than Cosy. This could even work better than Cosy, if you could run the big appliances like dishwasher and the washing machine during the off-peak slot. Having said that home batteries are probably the best option if one can install them coupled with an EV tariff.

My back of the envelope calculations suggest that we could run our whole house that consumes 8000 kWh per annum (including EV and an heat pump) on an average of about 20p even without solar and batteries. It's still more than double what it costs with our solar and battery setup and being on Octopus Go, but the Eco7 option would be considerably cheaper than being on a SVT.


16 * 435 watts PV
13 kWh Growatt battery
1 EV - Mercedes EQB
6 kW Aira Heat Pump
Bosch Induction Hob
Pod Point Solo 3 charger


   
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Batpred
 Batpred
(@batpred)
Noble Member Member
Joined: 2 years ago
Posts: 1151
06/06/2026 12:21 pm  

Posted by: @etchedpixels
↑

I actually think the fix for many people would just be a bigger battery but it's all about timescales and if someone tricked you into a product tied to overpriced vendor specific batteries or not. If you've got the flexibility then big batteries seem to be the winner with an EV tariff, dunno about agile.

Thanks, my impression is also that investing in a larger battery (if you are not tied into an expensive battery system) is currently the best solution for people combining EV with a heatpump. 

Hopefully grid storage will be added, enabling new tariffs that can work with small batteries.  

Posted by: @tim441
↑

Other considerations if adding a battery... do you want EPS? Emergency Power Supply may or may not be important to you. Ideally fully automated for whole home? But like everything it comes at a cost e.g. Tesla Powerwall or similar

I was lucky that I could add EPS for a very reasonable cost, as below. Solax, Sunsynk/Deye and Victron hybrid inverters have similar capabilities. 

image

The key for this type of systems is to use batteries with compatible BMS (in practice, same BMS). 

 


8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; G99: 8kW export; 16kWh Seplos Fogstar battery; Ohme Home Pro EV charger; Vaillant Arotherm Pro 7kW; 100Amp head, HA lab on mini PC


   
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