Hi, we have 16 x 365w panels, Gen 1 5.0 Hybrid inverter and 8.2kW battery. We have an EV but low mileage and a granny charger meets 95% of our needs. We are on Octopus Go and have no heat pump. We are all electric, with Harmoni wall heaters, ranging from 600W to 1.5kW. These are expensive to run and our house isn't very warm. I'm considering changing to Octopus Cosy, so we can run the heaters during the cheap sessions with the battery supplying most of our needs when the rate goes up. Does this sound realistic? The big problem we would have is the Gen1 inverter only supports one timed charge slot, so I'd need to look at a 3rd party app to cater for the three charge periods. Any advice would be appreciated.
AFAIK Cosy requires a heat pump ? Or is it for any electric heating ?
Might want to look at Tomato Energy - with an EV, they seem to quote (in my region) 5p for 6 hours overnight, and then a discounted rate 10:30 to 12:30 and from 10pm to 12pm. (I'm tempted, but haven't switched yet.) They don't do an export rate, so would have to use another provider for SEG - Octopus offer something like 4p when you don't import from them.
On using an external agent to manipulate charging slots: as long as you are not a technophobe, it's not hard to set up a raspberry pi to use the API to automate changes. That's probably cheaper long-term than using one of the online services. I think GE might be offering some sort of portal-based scheduling soon (but if it's closely integrated to a smart tariff, it might be annoying if you can't just tell it what you want explicitly.)
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#3Weasel
Octopus have not asked me what heat pump I have, or even if I have one.
If your inverter has only a single timed charge slot, then HomeAssistant and the GivTCP and PredBat integrations/addons might suit you. Its slightly techie to set up, but does the job
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#4Avenir
No HP required, as far as I know. The Tomato option sounds too good to be true, I'd wait at least a few months to see how that pans out. WonderWatt might be worth the subscription fee to automate things and would open up the option of using Agile.
The big issue with a Gen1 inverter and electric heating is going to be exceeding the max output of 2.6kw at the very expensive Cosy peak times. I guess you can model it based on current usage and see if you will actually be making a saving. Does it at some point become cost-effective to upgrade the inverter?
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#5geoffreycoan
Avenir The big issue with a Gen1 inverter and electric heating is going to be exceeding the max output of 2.6kw at the very expensive Cosy peak times
Agreed, but with only a single 8.2kWh battery @raybee would run out of stored battery charge in the peak period first before the inverter becomes the limiting factor.
All the advertising for Cosy says that you need a heat pump to get Cosy. I would imagine they would ask you for proof of the heat pump at some point in the signup process, like they asked for proof of MCS certificate when joining an export tariff (Flux in my case).
@raybee you don’t mention what your daily consumption is, base load plus the electric heaters. My guess is that it exceeds the capacity of your battery by a fair factor. You’d need to work out how much you think you use at different periods of the day to work out what tariff is best, but if you are regularly going to have peak rate import then Octopus Tracker or Octopus Agile may well be your best bets. Your battery should be sufficient to get you through the peak Agile price period but you would need some form of automation (Predbat, Wonderwatt, etc)
Or the Givenergy Web Portals new Smart Tariff (Beta) card where you can get it to track plunge price points and change the battery for you. it uses the 1st charge point and over writes it each time of charge.
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#7Avenir
The 8.2kwh battery is 100% DOD, isn't it? So it should last the 3-hour peak at 2.6kw discharge rate. You wouldn't be able to fully recharge it in the 3-hour cheap periods though, at the slightly lower recharge rate of 2.4kw.
Cosy Ts&Cs:
2.7.3 To be eligible for the Cosy Octopus tariff, you must have a heat pump or compatible low carbon heating system installed and operational at the property which we supply. Compatible systems are determined at Octopus' sole discretion.
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#8raybee
Avenir Thank. The indication I get from Octopus is that they would accept our electric heating system. I'm thinking these heaters would provide background heating. My wife had polio and has poor circulation in her lower limbs. We've found the best thing for her is a 400W halogen heater pointing at her legs. I'm happy with around 18C, so I think I could manage it without going much over 2.5kW.
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#9TimHutchings
raybee One other option you might want to look at is installing an A2A heating system (ie aircon unit/s). We have a 6kw Mitsubishi which 2 years ago cost £1800. It heats our whole 2 bed detached open plan bungalow. We've had it through 2 winters now (installed Oct 22), kept us nice and toasty, and has saved us a fortune. For every 1kw of electric it uses, it pumps out around 4.5kw of heat, and once up to the set room temperature, runs at between about 150w-600w, depending on the outside temp. It works at temperatures down to -14c. Last winter it used around an extra 8-9kwh per day on the coldest days, but much less in spring and autumn, and we're both at home during the day!
You don't have to have a big one like we have, as they come all different powers and prices and and you can have them positioned in different areas to heat the whole house. Tim and Kat's videos on YouTube will tell you more if you're interested. (Think they had them fitted after us). Oh and the other bonus is the nice cool house we have in the hottest periods of summer.
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#10pwdst
In case you are yet to invest in any kit, a relative with ME/CFS and who always seemed to feel the cold has found the 220W infrared heater absolutely perfect for keeping her warm. It's not super cheap but it absolutely sips at the power so it it easy to run off panels and batteries.
