ASHP running time and sizing

[Fly100]

RE lookin at this again as Im considering buying a Telsa Power wall to compliment my Solar array, which would in turn entitle me to the Octopus Tesla Tarriff. of 11.5p import and export.

I have had a go at the Heat Calc sheet a couple of times, but cant seem to get output with my figures. That said I do have some real world data. I have an Hour Metre on my boiler burner and over the last 4 years it has run for 500 hours per year give or take 20 hours. from there I can work the flow rate of oil and how many KW the Boiler produced that year.

 

14000 kw is my yearly requirement, devided by 180 heating days per year is 77kw a day COP of 3. 25kw a day. 

 

Am i miles off or just about there.

Thank you in advance.

 

FLY

[ProDave]

6 minutes ago, Fly100 said:

14000 kw is my yearly requirement, devided by 180 heating days per year is 77kw a day COP of 3. 25kw a day. 

That 180 heating days will not be equal.  Likely 50kWh per day on the coldest days, and considerably less at either end of the heating season.

 

No idea what the capacity of the Tesla is, but I doubt it is anywhere near 50kWh

[Fly100]

1 hour ago, ProDave said:

That 180 heating days will not be equal.  Likely 50kWh per day on the coldest days, and considerably less at either end of the heating season.

 

No idea what the capacity of the Tesla is, but I doubt it is anywhere near 50kWh

 

i wasnt planning on using the Power wall to to supply the ASHP it was the fact it give me access to the 11.5p Tesla Tarriff making my import cost reduce from 28p.

[Ferdinand]

I'm trying to get to grips with this and other questions for my own house.

 

As I read it, Tesla Tariff has a cap on usage at 9500 kWh from the grid per annum in day hours, at which point they make you switch. Does this affect you?

 

If your daytime consumption (from 07:00-19:30) grows beyond 9,500 kWh per year, per-Powerwall-installed, you will be prompted to choose an alternate tariff that better suits your usage.

 

Please note, if you own electric vehicle(s), scheduling your vehicle charging to occur outside of the daytime hours (I.e. charging any time between 19:31 and 06:59) will transfer a significant amount of your household consumption to off-peak hours. Whilst this reduces your daytime usage as a Tesla Energy Plan customer, this practice is also helpful for reducing the peak demand on the national grid, which further helps reduce national carbon emissions.

https://octopus.energy/tesla/tariff/#/calculator

 

Have you run it through the Tesla/Octopus calculator?

 

A second issue is whether the 11p/11p tariff can be switched by Octopus and at what notice?

 

(I'm on a FIT at about 14p per kWh for exports, so would not consider something dependent on a supplier's goodwill.)

 

I think the current capacity of a Powerwall 2 is 13.5 kWh, and you install 2.

https://www.jojusolar.co.uk/batteries-smart-grids/tesla-powerwall/#:~:text=A Tesla Powerwall 2 has,appliances are running at once.

 

Having the option of charging the Powerwall to feed your ASHP in the day would give you a Plan B if you hit the daily limit on the tariff.

 

To me a case for an ASHP dependent purely on a particular tariff sounds a shaky foundation - you need to know it will be worthwhile if that tariff eg doubles in price at some point soon.  

[Fly100]

7 hours ago, Ferdinand said:

I'm trying to get to grips with this and other questions for my own house.

 

As I read it, Tesla Tariff has a cap on usage at 9500 kWh from the grid per annum in day hours, at which point they make you switch. Does this affect you?

 

If your daytime consumption (from 07:00-19:30) grows beyond 9,500 kWh per year, per-Powerwall-installed, you will be prompted to choose an alternate tariff that better suits your usage.

 

Please note, if you own electric vehicle(s), scheduling your vehicle charging to occur outside of the daytime hours (I.e. charging any time between 19:31 and 06:59) will transfer a significant amount of your household consumption to off-peak hours. Whilst this reduces your daytime usage as a Tesla Energy Plan customer, this practice is also helpful for reducing the peak demand on the national grid, which further helps reduce national carbon emissions.

https://octopus.energy/tesla/tariff/#/calculator

 

Have you run it through the Tesla/Octopus calculator?

 

A second issue is whether the 11p/11p tariff can be switched by Octopus and at what notice?

 

(I'm on a FIT at about 14p per kWh for exports, so would not consider something dependent on a supplier's goodwill.)

 

I think the current capacity of a Powerwall 2 is 13.5 kWh, and you install 2.

https://www.jojusolar.co.uk/batteries-smart-grids/tesla-powerwall/#:~:text=A Tesla Powerwall 2 has,appliances are running at once.

 

Having the option of charging the Powerwall to feed your ASHP in the day would give you a Plan B if you hit the daily limit on the tariff.

 

To me a case for an ASHP dependent purely on a particular tariff sounds a shaky foundation - you need to know it will be worthwhile if that tariff eg doubles in price at some point soon.  

 

I can answer some of your questions. Most of my Heating demand is pre 7am so I can shift the underfloor back an hour to cover that part totally off, my calcs would put my usage with an ASHP to approx 8000KW per anum. That and we have slightly thicker screed so one heat cycle per day normally. Also I would probaly keep the oil boiler for Dec / Jan anyway.

From a FIT tarrif view Im on the last Tarrif of 4.5p & 5.5p for export and generation. Using the Calculator on the website reduces my bill by approx £900 per annum this does not include an ASHP.

Edited March 13, 2022 by Fly100

[Ferdinand]

@Fly100

 

Great to see you being as thorough as you can 🙂.

 

I did huge thread earlier, but it needed to be made digestible - so I'll need to revisit.

 

F