Talk Morgan Forums Community The Malvern Arms Off grid and power walls etc

Our long awaited Tesla Powerwall (13.7kWh) arrived last Monday to be met with a relatively sunny week. Consequentially our typical winter daily consumption of 20kWh was only 50% from the grid for the week, we have a 6kW solar set up that faces SW and also a Solar iboost. Nothing went back to the grid at the measly 6.4p /kWh SEG.

Our historical average daily consumption drops 50% from March to Oct as we turn off our storage cooker that also partially heats the kitchen, so I am pretty confident we’ll be off grid for the majority of that period.

By my reckoning I should be near a 10year payback at current tariff levels, which are going to go up making payback shorter.

We waited 1 year for the Powerwall and at the start interest rates were near zero making this a no brainier investment, but as rates have come back up the financial gain is certainly diluted.

It’s quite a complex benefit model with lots of variables and if you throw an EV into the mix it gets even more complex, even so I’m happy with the investment.

Our daily average pre the batteries was from May to Oct 4 kWh then Nov 9, Dec 10, Jan 13, Feb 8 & Mar 6.

The average daily output from the array is 11.25 but obviously in winter bad days can be 0.2 kWh.

So I'm hoping that we will easily be off grid May- Oct.

On that basis our pack of 2 batteries is 4.2 kWh in total . But we can expand it by another 3 batteries at I guess £1k a pop.
Glad to see yours is working well.

Yesterday I signed up to the Octopus Energy EV tariff. It’s a beta test product but it offers power at 10p /kWh for 6 hours at night up to 0530hrs. So the plan is to use these hours to -
1.charge the wife’s PHEV
2. Top up the Tesla Powerwall (13kWh)
3. Run the dishwasher on timer.
4. Give the storage cooker a boost
5. Give the HW a boost through the iBoost

Then the house will run off the Powerwall and solar in the day.
The next washing machine we buy will hopefully come with a timer.

I had that tarif when I had the Tesla. Octopus are a great company to deal with.

Do you need an ev to get it?

Basically yes, but a PHEV will do it along with a charger like a Zappi.

A further update.

In Jan we consumed 267 kWh.
We bought off the grid 143 kWh
The PV panels supplied 48 kWh for self use
The batteries supplied 76 kWh
So 54% bought in . The batteries saving 28%

We also exported 3 kWh when the PV panels exceeded demand & the batteries were full.

In Feb with the better weather till the 8th we consumed 79 kWh
Bought in was 16 kWh
Self use ex PV 28 kWh
Batteries 35 kWh
So bought in fell to 21% & batteries supplied 44%
The last 3 days we have been effectively off grid importing less that 0.75 kWh per day.

We also exported 10 kWh

Blimey John, that's very impressive, you clearly have a much lower overall demand than we do. We usually use around 12 to 14 kWh per day in winter, excluding the EV.

By contrast, we only managed to produce 109kWh out of a total consumption of 625kWh. (of which 166kWh went to charge the car), so only 18% of our needs were met by the panels.

Based on the coast with the roof facing directly south helps.

YTD we boughtt in only 44% of the power used. The panels supplied 25% and the batteries 31% of the usage.
Daily consumption off the latest meter readings is down from 7.5 kWh /day in 2022 to 3.7kWh/ dayay in 2023.
The payback over the first 3 months shows a 9.9 year crude payback and falling.