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

Here’s February’s result

House consumed 550 kWh
Car Consumed 55kWh
Cost of grid supplied electricity was £45.00 (excluding standing charge)
PV generated 266kWh of which Exported was 22kWh.

That’s on Octopus Go tariff charging the Tesla battery and car between 0030 and 0430hrs.

I got a £50 referral voucher on joining Octopus and with the govt £67 rebate, they owe me money.

Very good. We’ve just joined Octopus, and waiting to get a smart meter. May get an EV later this year.

Did you get a friend to refer you? You each get £50 credit if you use the referral code.

No, we missed out on that!

We've recently received a £200 alternative fuel payment credited to our account with Octopus. Apparently it's simply because we don't have mains gas

Crediting to our Octopus electricity account obviously works fine for us but not for 's daughter who has oil fired heating. Her £200 payment also credited to her Octopus electricity account, leaves it presently around £400 in credit. She now has the hassle of asking them for a refund to buy oil.

I am also on Oil. My Electricity supplier EDF wrote to me advising they would credit £200 to the account from which they take my monthly Direct Debit.
On 23 Feb EDF did just that one week later. At no time did they suggest that they would add it to my EDF account.

I assume your daughter has an alternative payment method.

As an aside my oil price per litre is about double what it was before the energy crisis. If you take the" additional" cost to me this winter the £200 represents about 20% of the"extra" cost.

That's interesting. We did have an email from Octopus advising their receipt of government payment but added they were not aware specifically why. I had to look up on government website to see why we qualified which may have included heat pump heating. Ironic this uses only electricity though

It seems that power providers have differing policies on such payments and are not always aware of their electricity customers alternate fuel.

Just trying to do the math's that relate to battery storage....
According to various figures above then battery storage equates to roughly savings of say 34% of consumption.
If you consume 5000 kwh of electricity then 1700 kwh of energy will be supplied by battery.
If we used a rate of 34p per kwh (peak rate cost so not taking into account off peak cost), then 1700 x 34p = £578.00 per year saving.
And a Tesla Powerwall 2 costs circa £11000.00 to install.

19 year return on investment??? Tesla Warranty is standard 10 years.

Am I missing something in my calculations?

My Tesla Powerwall was £8k fitted but I did wait a year for delivery.

I regard the battery as key to the success of the solar throughout the year so really need to look at the combined cost of £17k.

I also think it’s a mistake to just concentrate on the warranty period e.g. I have friends who have had the same PV system for 20 years.

My Tesla is programmed to charge from solar and then the grid at off peak. The dishwasher and washing machine also run during off peak hours. The storage cooker also gets a boost off peak. So the house rarely runs on peak rate electricity.

Likewise, the PHEV only charges on surplus solar or off peak.

We use approximately 6500 kWh per annum in the house and about 750kWh for the PHEV.

The battery means that from April to September we should be using significantly reduced grid power but we haven’t been through a year yet.

So an estimate would be -

No solar or battery = 7250kWh x 34p = £2465 (assuming the cost of electricity doesn’t rise, I’m betting it will).

5 months at Feb rate of grid use would be approx 1670 kWh.

1670 x 12p = £200

Then say 7 months averaging 50% less would be approx £140

So, saving is approx £2465-£200 -£140 = approx £2100 per annum which gives system payback of approx 8 years.

Allowing 25% contingency would give 10years payback on the system.

In all honesty I didn’t think about payback, at the time of ordering interest rates were rock bottom and I couldn’t think of a better annual return on £17k.

Hope this helps.

Life and replacement cost of batteries? - 19 years is a long time.