Eddi alternative?

Slinky

Have been quoted £500 for installation of an eddi alongside our intended solar panel installation. Thinking about this, is there such a thing as an immersion switch which can be controlled by an app? Just thinking that it might be a cheaper option to run the hot water heating on a more manual system utilising cheaper gas in the winter and excess solar  as and when its available, without having to visit the airing cupboard, and more importantly, forgetting to switch the immersion off manually by accident as has happened before and not been discovered for several weeks..... Could also taken advantage of cheap TOU tarriffs to heat overnight.

Magnitio

I installed a 1.5kW immersion and control it with a Tapo P110 plug. Easy to use and a relatively low load that the panels or battery can supply without issue.

Screwdriva

Yes, available here. Works great during Agile "plunge" pricing events in the early hours as it can be timed. 

Alnat1

Would depend on your tariff but you can get paid more by exporting the excess solar and it will more than cover your gas costs. That's the position I'm in at the moment.

Not as good for the planet but I couldn't justify paying extra for something that will actually mean heating water costs more and I'll use gas to heat the tank in winter anyway.

1961Nick

Now that we're into the warmer weather & DHW is often being run independently from the CH, the calculation for using gas to heat DHW changes significantly. A 92% efficient boiler is likely to achieve around 80% overall during a DHW only heating cycle. On top of that there are the transmission losses getting the water to the HW cylinder coil. When the tank reaches the desired temperature & the boiler shuts down, there's a considerable amount of hot water left behind in the 22mm or 28mm pipework that's necessary for the CH but is too large for efficient HW heating. The overall picture is possibly close to 70% for gas & 99% for electricity during the summer. That would make the true cost of using gas to heat DHW around 15p/kWh at current prices.

Anyway, it's something to consider when comparing SEG rates with the true cost of gas water heating.

Screwdriva

1961Nick said:

Anyway, it's something to consider when comparing SEG rates with the true cost of gas water heating.

Useful to know. Good thing I'm on gas tracker at ~.05p.

1961Nick

Screwdriva said:

1961Nick said:

Anyway, it's something to consider when comparing SEG rates with the true cost of gas water heating.

Useful to know. Good thing I'm on gas tracker at ~.05p.

I've just run some numbers on my heating system to see what percentage of the energy is left behind in the pipework & it's more than I thought..

24m of 28mm copper pipe between the boiler & cylinder.
70C on the flow side & 55C on the return is an average of 62.5C
18C ambient.

The above works out at around 0.9kWh on a 'burn' of 5.9kWh... or 15%.

All a bit crude but it illustrates the hidden cost when there's unutilised energy.

Alnat1

For hot water (no heating on now) I used 4.9kWh gas yesterday at 4.96p per kWh, let's call it 25p. Even if only 3kWh of electricity would have heated the same amount of water, I would have lost 65p of export payments. Using gas saved me 40p.

Why would I pay £500+ to have a solar diverter device fitted to make me lose money? 

Slinky

1961Nick said:

Now that we're into the warmer weather & DHW is often being run independently from the CH, the calculation for using gas to heat DHW changes significantly. A 92% efficient boiler is likely to achieve around 80% overall during a DHW only heating cycle. On top of that there are the transmission losses getting the water to the HW cylinder coil. When the tank reaches the desired temperature & the boiler shuts down, there's a considerable amount of hot water left behind in the 22mm or 28mm pipework that's necessary for the CH but is too large for efficient HW heating. The overall picture is possibly close to 70% for gas & 99% for electricity during the summer. That would make the true cost of using gas to heat DHW around 15p/kWh at current prices.

Anyway, it's something to consider when comparing SEG rates with the true cost of gas water heating.

Thanks for this. Our gas boiler is in the cupboard backing onto the airing cupboard so pipework is as minimal as you can get.

Slinky

Thanks for all your comments, eddi has been consigned to the scrapheap of possibilities.

EcoScruples

I wish I'd have thought about this a little more before I had mine installed.
The only comfort I take is that it reduces my need to burn oil in my boiler to heat water daily all year round.
I can also reduce the boiler flow temp as it doesn't need to be on high to get the water temp to 60 degrees thus prolonging the life of my boiler by a few extra years.