There are two of us and after leaving it to reheat when the temperature drops we now reheat at 6pm. Draws about 1.6kWh. We have the sensor at the highest of four positions in the 210l Solar cylinder. The pump drives both circuits. Nothing worse than my wife getting the temperature drop when it needs a reheat!
The bigger cylinder was in case someone wants a bath.
Phil
I had a look at hot water heat pumps yesterday. The best option for us is a system that retrofits the hot water tank and has a small outdoor heat pump that is copper-plumbed back to the water tank. It’s about $7K installed. It would have a microchip that talks to the solar system and increases the tank temperature when there is excess solar, to effectively give some local storage.
However, with our reasonably large solar array going in, their feeling was that we would be close to zero power bills without the hot water heat pump, just by using a timer on the existing hot water tank. We will try with setting the timer for winter from 11am to 5pm, when the electricity rate is lower, with a top up at 6am to 7am on the lowest night rate. We’ll try that for 6 months and have a good option to fall back on for the hot water heat pump if needed.
Interesting thread, chaps.
Toyota’s rival toTeslas Power Wall maybe of interest, although it looks like it will not be available outside Asia until next year.
That’s quite an interesting development. I was talking with my solar provider the other day and he mentioned that the emerging technology would also enable car batteries to power home appliances as a back up.
Mike, this is what the new Ford F-150 lightning pick-up truck can do.
It’s complex for the power utility to administer but makes a great deal of sense.
Best regards, BF
Mike if you get the right system you won’t regret it. Our bill went from around a $1k per quarter to under $250.
It’s getting installed in 3 weeks time, we have gone for an even larger 23 panel (8.7kW) system and I’m really looking forward to it.
We have already changed power retailers to get a better solar export rate, and even just the change in rates with the new provider has reduced our bill by $80/month (as it favours off peak use, which we can inmate as we are both at home during the day).
The whole thing is up in the air (again) here apart from reducing the rate they pay for your excess power they now want to change you a flat rate per month to use their lines to send it back.
I’m going the whole hog on our new build and including a battery, I’m sick of them changing their minds every 3 days.
Yeah, I’ve looked at the economics of a battery and didn’t fell there was a strong case, but as exporting becomes less attractive, a battery does start to look better. Certainly, having more independence from the power companies and better self resilience with a battery is starting to look more appealing.
Hi Phil,
It’s utterly marvellous!
First, our electricity consumption from the grid has fallen to 1kWh/day, all of it effectively transient rounding errors as the Tesla Gateway balances fluctuating household demand with fluctuating solar output and any power flows into or out of the battery. This is before taking into account the 25+kWh per day that we have been exporting throughout May.
The second benefit has come as a bit of a surprise. Once you own a Powerwall in the UK, you are entitled to join Octopus Energy’s Tesla Tariff. Up to this point, we had been on a flexible Octopus tariff which charged us almost 30p/unit of consumption and repaid us 7.5p/unit exported.
If you own a Tesla car or a Powerwall, you can switch to the Tesla tariff, which we have done. Electricity imports cost only 11.24p and yet we also get 11.24p for all electricity that we export to the grid.
This special tariff effectively reduces the cost of electricity by over 60%, while increasing the price at which we export by over 50%/unit.
All in all, we are now being paid during the summer months and will pay it all back (and a bit more) in the winter months.
We genuinely couldn’t be happier.
Best regards, BF
Hi @Bluesfan
What a great report! I’m getting a SMET2 meter (currently SMETS1) in about 5 weeks. I know I will have to switch to another supplier so I’m just getting the meter done ahead of the switch. Also the gas meter is going as we have had the heat pump installed. Our daily hot water costs 1.6kWh.
I was offered a Powerwall 2 ordered a year ago for a customer who recently passed away. It should arrive by 26 January 2023 when the Solar goes in. I will definitely switch to Octopus and that tariff looks great. They must keep it under wraps as I have not spotted it.
I must admit to toying with V2H either from Indra (if I get on their trial) or Wallbox. £4K would be better than the cost of Powerwall. Wallbox claim to have Mains Backup if you also purchase the automatic grid disconnect for when the grid is down. Indra said that working with the Powerwall requires careful setup in order to ensure the V2H does not charge the Powerwall unintentionally!
Phil
I’m struck by how much of the focus here has been on return on investment, when the real opportunity and necessity is to use the sun (an incredible resource) instead of fossil fuels.
Three years ago I installed 14 300w panels and a 4.8kw battery, together with an Eddi.
On a south facing roof, with no obstructions, I am getting 4,200 units of electricity per annum, out of a total annual electricity usage of just over 6,000 units. (180 sq. m. house using oil for heating).
Investment was €12,300 less a government incentive of €3,800 (dependent on including the battery) and payback at the time probably looked liked 12 years plus, but now less than 8, and falling.
I get great satisfaction from monitoring the contribution of the sun every day and I have also been able to reduce our oil consumption as a result my heightened awareness of how the sun behaves and maximising sun ingress in every room throughout the day, having installed external house insulation. Heat comes in through the windows and stays long into the evening.
I realise that many of you are more concerned with dispersing heat and heating pools etc, but there are some advantages in living in a cooler, wetter climate!
Stuff these gorging energy companies and politicians arguing over who’s fault it is think it’s time to add a battery. There’s no way I’m not including one to new build, even if it takes 20 years to recover the cost it sends a clear message to both of them.
Intelligent vehicle to home (V2H) seems to be where we are going, as vehicle batteries are so large, even in comparison with a Powerwall. As an example, our Powerwall has a capacity of 13.5kWh, while the Skoda Enyaq has a capacity of 82kWh.
A couple of caveats though. First, I don’t think that the standard European & N American charge cable connector called CCS is able to carry the 2 way communication channels necessary for V2H. Second, while the Japanese cable connector called CHADEMO can support V2H, the Nissan Leaf is probably the car with a battery that is the least able to support the extra load from V2H.
We are going to wait about 5 years before the cars, the connectors and the charge points are all ready for reliable V2H.
Best regards, BF
Thats a great outcome - nice one
For me, it’s both really. Going solar has always appealed for environmental reasons, but it has only become affordable for us in recent years in terms of actual cost and having enough cash available. Indeed, it helps now that it gives as a financial return that is better than having the money invested as well.
We are getting a 8.7 kW system installed in a few weeks and are going to see how close that gets to a zero annual power before revisiting a battery (which is a whopping $20K, not much less than the whole solar array). A battery is very appealing, but the cost and technology doesn’t feel quite there yet.
Thanks for this - has prompted me to see if we could take advantage of it for the whole family (though might need two power walls, kerching 
£££). And would mean getting 10-12p per kWh income from our wind turbine too in places of deemed 50% export- although the shared supply and wind turbine might prevent us from going for this.
Hi BF, I thought of the Tesla Tariff as better because it
Best
Phil
Hi Phil,
Great summary.
Two caveats though:
Once export and import prices (11.24p/unit) are the same, there is less incentive to generate your own via more solar/wind or reduce your consumption. The case for us to do a “phase 2” with more solar + a Mixergy hot water tank with solar surplus immersion heater is now weaker vs when we imported at 30p/unit.
Tesla controls the Powerwall, so you lose the ability to reserve say 30% of the battery capacity in case of a power cut.
Overall though, we are still really pleased.
Best regards, BF