Iboost+ Eddi etc, solar diverters why? What am I missing?

[ericmark]

I was watching a video about a solar installation. And he was saying how he wanted the Eddi mounted, so easy to access, it was a massive installation with loads of battery power, and well over the amount of solar panels to what I have, so maybe that has some bearing on the use of a solar diverter?

However, I pay 8.5p/kWh for off-peak, and get paid 15p/kWh for export, so I am better off using off-peak to heat the water.

Some of the tariffs do have a three-way split, with off-peak, standard, and peak. This can mean 17.1p off-peak and 10.54p standard export, so one can pay more for off-peak to what one gets for export, I see the Eddi is more involved to the iboost, and if the panels are large enough to get a reasonable winter output, then can see why the likes of underfloor heating is used from the solar panels, but my solar panels 6 kW will not produce enough for general home use in winter, so no point having any diverter for winter use.

So what have I missed?

 

[JohnW2]

.... so no point having any diverter for winter use.

This all seems to be amazingly complicated If one has such a gizmo, cannot one turn it off during Winter?

 

[ericmark]

It would auto turn off in the winter, there is a CT coil, and I can set the point where it starts to use solar power. I have it set at 200 watt. The original idea was when export was not monitored, but assumed, so if you had a 3.5 kW solar array it was assumed 1.75 kW exported, so the more you used, the more one gained, they also paid silly amounts for export, something like 40p/kWh, and then we had a meter to measure solar production rather than solar export, but early 2023 it decided all new installations needed a smart meter, so today you only get paid for what you export.

As said, the Eddi does a bit more than the iboost+, but both the same idea, they use power in the home to heat DHW rather than export it.

But the tariffs mean, for me at least, using off-peak I gain more than using solar export, so I suppose the best idea would be to remove the batteries in the wireless CT coil. I note the eddi has a PT100 sensor on the side of the tank, so maybe it can be set so it heats the tank up more at night?

The over-night (off-peak) on mine is set in 4 sections, 2 for summer and 2 for winter, and the week days and weekends are separate programs. Now fitted it seems pointless to replace it with a simple time clock, the gains are not enough to worry about, but the same applies to fitting them in the first place, I am losing 6.5p/kWh with my Go tariff, and someone with Flex tariff would gain 6.66p/kWh it would take a very long time to pay for the device at those rates, I use around 14 kWh per week to heat water, so less than £1 a week, since for me already some off-peak is used, more like 50p per week, summer only, so around £20 per year, and it depends on the tariff as to if this is a gain or loss.

Next year I may change tariff, so seems pointless looking forward 10 years. Artisan Electrics did a video, and I thought until watching it, I had simply made a mistake, but watched the lengths he went to fitting it, this is with 9.3 kW of solar panels, and 27 kWh of battery storage, makes my 6 kW and 6.4 kWh seem rather small. My battery is not fully charged without using off-peak until around 11:30 am

Now I use off-peak, it is charged earlier, so back then

this was what went on that day, so even with my system had I got such a huge battery I would have had space left, but since only using 10.6 kWh next day it would be full, but the next day I only exported 0.7 kWh, so unless using off-peak, I would have been left with very little DHW.

So to ensure a supply of DHW every day central heating not running, having off-peak heat the water makes sense. So using an expensive device to use solar, seems to me, I have waisted my money. A simple time clock would have been better.

 

[StephenStephen]

Edited: When we got deemed export feed in tariff, it made sense to install an Eddi - I could get paid for export that I was actually using to heat water.
Then when many of us moved over to metered payments for export, it made economic sense to heat water using either gas, or low rate electricity.

I have an Eddi.

I haven't used it in years...

...except as an additional IHD

If I ever went back on the Agile tariff I'd probably use it - you can set an Eddi up to heat water when the cost rate goes below a certain amount.

 

[Murdochcat]

Solar divertors are for people like me who have PV but no battery storage AND can be very productive on sunny winter days

 

[ericmark]

Solar divertors are for people like me who have PV but no battery storage AND can be very productive on sunny winter days

I had not considered people with no batteries, and yes, can see how storing as hot water makes sense. However, it would depend on tariff even then, seem to remember some problem getting paid for export with new installations without batteries, as I said I am being paid 15p/kWh for export and paying 8.5p/kWh for off-peak import, so better off using off-peak and exporting.

Interested in knowing what if anything you get for export and import?

 

[Murdochcat]

I had not considered people with no batteries, and yes, can see how storing as hot water makes sense. However, it would depend on tariff even then, seem to remember some problem getting paid for export with new installations without batteries, as I said I am being paid 15p/kWh for export and paying 8.5p/kWh for off-peak import, so better off using off-peak and exporting.

Interested in knowing what if anything you get for export and import?

No FIT payments

 

[ericmark]

No FIT payments

That explains it, so for you, the eddi water heater must really pay for its self. I had 18 months without any feed in payment, unfortunately the immersion heater was only 9 inch long, so not much hot water, and I was loosing money as battery too large, so still 70% charged when the sun came up, with off-peak charging, but the smaller battery was running out before the off-peak kicked in.

Now looking at yesterday, still 57% battery left when off-peak kicked in, and the morning it dropped to 89% before solar production exceeded use, but since pay 8.5p/kWh for off-peak, and get paid 15p/kWh for export, that 89% is not a problem, it was however when not getting paid for export.

I found with no payment for export better with a single rate tariff, the off-peak was not really helping, but as soon as I started to be paid for export, that changed, my account balance seems to be growing all the time, but as yet not done a winter with larger batteries and export payment, so not sure what winter will do to the account balance.