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

David,
they need in my opinion good insulation to work well, and they do work well as I know from firends in Sweden & Finland who have them.

They run as said at lower temps vs gas boliers so must be on longer to keep the house warm.

I guess they would work but you would have to larger units to compensate the heat lost & therefore the cost ould be higher. I would if you can insulate first.

I would contact an installer to get their view.

Thanks John, this is my suspicion - using heat pumps with a house that is already highly insulated, eco or nearly passive is a totally different proposition to an old Cotswold stone farmhouse. I know this has been raised by many as the UK housing stock is older on average than many countries. But I am more interested in our personal options. My wife is disabled and gets cold easily so lowering ambient temp is not really an option either. Will keep digging …

I have a small amount of experience with heat pumps but it was a long time ago.
We used to import ground source heat pumps from Denmark. you needed alot of land to make it worthwhile. Big areas of underground matter.
Believe it or not, they also gradually loose efficiency as they take the heat from the ground, the ground does actually reduce in temperature so the system gets less effective.

More up to date experience. A friend has a house in Portugal. The air heat pump heats their swimming pool. It's very good at raising the temperature by two or three degrees. The pool is covered in black material which also helps. But the heat pump can't get the water actually hot as it's working on the difference between the temperature inside and outside. Expensive now that electricity is so expensive as it uses alot.

I'm told most Scandinavian countries where they are common use other sources (wood burning?) to actually heat the house, the pump is to maintain a background comfort.
Only what I can come up with for the discussion, not a dissing of heat pumps in total.

Short video about cold weather and heat pumps - the comments below it are interesting too....

https://www.youtube.com/watch?v=P2WT80noINQ

and one about noise....

https://www.youtube.com/watch?v=GKDF5a47eJk

Yes admit it is newish Keith, just coming up to two years. It's a Grant Aerona with 10 year guarantee.

Interesting discussion on ASHPs.

As I said before, I’m sticking with gas for my heating for now. One of the reasons is that we already consume substantial amounts of electricity in winter (typically 20kWh - 30kWh per day) partly depending on the amount we need to top up the EV. The EV charging is currently mainly on the Octopus Go tariff between 0030 and 0430 at 12p/kWh which is critical to keeping costs down. We also top up our storage cooker and run the dish washer and washing machine during off peak. To help we have a Tesla Powerwall that tops up off peak and from solar and that runs the house during the day. At the moment the system is nicely balanced and we very rarely use peak rate electricity.

The downside of Octopus Go is the peak rate charge of approx 42p/kWh and this is the rate an ASHP drawing possibly another 10-15kWh per day would often run at.

So it seems to me that the best tariffs for EVs are not necessarily compatible with the demand cycle for ASHPs and maybe the electric universe isn’t quite here yet?

I should add to the previous post that while a condensing gas boiler is 90% efficient and an ASHP is 300% efficient (COP of 3) the gas tariff per kWh is only approx 1/5 of the peak electricity tariff. So the ASHP would need to be even more efficient to present me with a saving.

Some observations on the Tesla Powerwall 2 battery system.

We’ve had this system installed since January and it’s been pretty impressive so far.

Nominal maximum storage is 13.7kWh and there’s a maximum discharge threshold you can set to hold power in reserve for a power cut. It seamlessly steps in during a power cut and maintains power for the whole house.

It monitors the weather and learns your usage patterns. For instance we set it to top up overnight on cheap off peak electricity and then the house runs on the battery and solar during the day. If the next day is forecast to be sunny it automatically reduces the amount it takes from the grid overnight, so for very dull days it loads up to 100% before morning and for bright tomorrow’s it takes no charge over night. So far it’s not made a mistake.

Since it was installed (in conjunction with our solar) we have consumed 1.8 MWh and 0.84 MWh has come from solar. As far as the grid is concerned we’ve only spent spent £11.10 on peak rate electricity during that period, the rest of grid consumption has been at 12p/kWh. Now the winter is behind us, I would expect any grid usage to drop dramatically.

Another feature of the Powerwall is “storm watch” where you can set it to automatically load up from the grid in anticipation of a storm, this is useful for us as we have a lot of trees and overhead power cables.

It’s not cheap but it’s definitely “smart”.

Impressive but as you say not cheap. My dumb cheapo system at £3.3k is now delivering in April 92% from the batteries & PV. We only have 4.2kWh of battery & a 3.6 kWh array. I couldn't see how such a large battery would payback, you must have a huge system to use 1.8MWh in 3 months. We have generated 1.7MWh in 4 1/4 years.

I'm guessing it's good to keep some manual control over the system rather than relying on the "computer says no" aspect of "smart" systems.