Solar IBoost+ experience

x4dow

With 16.5p export and off-peak import rare of 9.5p the iboost isn't a great investment for me and I would never had bought it at full price as 80+% of my cylinder heating is at night from grid (actually makes more sense to export excess at 16.5p). But without one, I might get in the situation where I might need a manual boost in the evening at full grid price, so diverting excess to top up temperature would still bring some returns, not just £350 in any time I'd expect it to live. 

I found a iboost+ one on FB sealed n brand new for £100 and done quick maths and seems to be worth as it only has to divert about 650kWh (peak top ups of heat are worth it as we shower mostly at night and solar battery won't stretch to that most days)
So I gone ahead and bought it. 

Now slightly disappointed at how noisy it is (my cylinder is in a airing cupboard in my bedroom and the fan is always on when the heating is on (unlike the paperwork says it should)

Might get some sound proofing material and shapenit like a túnel around it. Allowing airflow but dampen the sound. But if thisnunit fails, I just going back to a bog standard timer 

JKenH

My iBoost failed 3 times. First time, it was just the fuse inside the unit. Second time it was an electrical component costing a few quid which a friend diagnosed and replaced for me and third time was last summer just about the time I switched to Octopus Flux, so I have now taken it out the system. Marlec would in theory be able to replace the component for a lot less than a new one but whether they will is another matter. Might be worth asking though.  If you have any electronically minded friends you might be able to get it fixed cheaply. 

I should point out that my IBoost was not wired in accordance with Marlec’s guidance of being close to the cylinder (is it 3m?) as it feeds two separate hot water tanks located about 16m apart with wiring runs (upgraded cable to reduce voltage drop) over 20m . 

pensionpawn

I have had an Immersun for over 8 years however I passively retired it last May when I moved to Octopus Flux. Why would you divert spare solar to minimise gas import at 7p when you can be paid 18p / 29p to export it? The only advantage they offer now is "trickle charging" the UFH in my study room (ex internal garage) where losing 18p of export is preferable to paying 29p for import. However that said, with these negative temperatures, anything other than throwing full beans at the UFH is just pi$$ing in the wind!

Petriix

It's really important to remember that any 'savings' from an iboost or similar cannot be measured by how many kWh you divert but by how many kWh of the cheapest alternative water heating you avoided; and those are definitely not the same. Today, with export prices at 15p and off-peak imports at 7.5p it's only in unusual circumstances that any diversion would make sense. The best thing is to minimise usage and maximise exports. 

paul991

yes  but  using clean electricity to heat water rather than gas .As  heat pumps replace gas boilers more and more water will be heated this way

JKenH

Petriix said:

It's really important to remember that any 'savings' from an iboost or similar cannot be measured by how many kWh you divert but by how many kWh of the cheapest alternative water heating you avoided; and those are definitely not the same. Today, with export prices at 15p and off-peak imports at 7.5p it's only in unusual circumstances that any diversion would make sense. The best thing is to minimise usage and maximise exports. 

In many cases what you say is correct and in our case, being on Octopus Flux, we are better off heating our water on a cheap overnight tariff than using a solar diverter. The daytime export rate is similar to Flux import (2-5am) but we shower in the mornings and so use the water soon after it is heated rather than leaving it to cool down in the tank. If your personal hygiene regime dictates you shower in the evening or when coming home from work and/or you wash up by hand in the evening then heating your tank from afternoon sunshine can make sense (depending on tariff) as you lose less heat from the tank. 

If you are on a very cheap overnight tariff like IOG (7.5p) and are paid export at 15p/kWh then, yes, ditch the diverter.

pensionpawn

Petriix said:

It's really important to remember that any 'savings' from an iboost or similar cannot be measured by how many kWh you divert but by how many kWh of the cheapest alternative water heating you avoided; and those are definitely not the same. Today, with export prices at 15p and off-peak imports at 7.5p it's only in unusual circumstances that any diversion would make sense. The best thing is to minimise usage and maximise exports. 

I have been trying to convince so many of this over the years! If your solar divert is diverting 3kWs on a sunny day, it's not saving you a penny! Another way of thinking about it is that on a cloudy day you may only have 500Ws spare. In this instance the saving is 3kWs (the rating of the IH element) minus 500 Ws. This is because without the solar divert you would have to energise the coil at 100% and pay for 2.5 kWs of import. It would take six times longer to heat the tank, however at least it wouldn't cost you anything (assuming that the divert had already paid for itself!)

pensionpawn

JKenH said:

Petriix said:

It's really important to remember that any 'savings' from an iboost or similar cannot be measured by how many kWh you divert but by how many kWh of the cheapest alternative water heating you avoided; and those are definitely not the same. Today, with export prices at 15p and off-peak imports at 7.5p it's only in unusual circumstances that any diversion would make sense. The best thing is to minimise usage and maximise exports. 

In many cases what you say is correct and in our case, being on Octopus Flux, we are better off heating our water on a cheap overnight tariff than using a solar diverter. The daytime export rate is similar to Flux import (2-5am) but we shower in the mornings and so use the water soon after it is heated rather than leaving it to cool down in the tank. If your personal hygiene regime dictates you shower in the evening or when coming home from work and/or you wash up by hand in the evening then heating your tank from afternoon sunshine can make sense (depending on tariff) as you lose less heat from the tank. 

If you are on a very cheap overnight tariff like IOG (7.5p) and are paid export at 15p/kWh then, yes, ditch the diverter.

However if you have gas, you use that instead at 7.5p whenever you need hot water.

JKenH

pensionpawn said:

JKenH said:

Petriix said:

It's really important to remember that any 'savings' from an iboost or similar cannot be measured by how many kWh you divert but by how many kWh of the cheapest alternative water heating you avoided; and those are definitely not the same. Today, with export prices at 15p and off-peak imports at 7.5p it's only in unusual circumstances that any diversion would make sense. The best thing is to minimise usage and maximise exports. 

In many cases what you say is correct and in our case, being on Octopus Flux, we are better off heating our water on a cheap overnight tariff than using a solar diverter. The daytime export rate is similar to Flux import (2-5am) but we shower in the mornings and so use the water soon after it is heated rather than leaving it to cool down in the tank. If your personal hygiene regime dictates you shower in the evening or when coming home from work and/or you wash up by hand in the evening then heating your tank from afternoon sunshine can make sense (depending on tariff) as you lose less heat from the tank. 

If you are on a very cheap overnight tariff like IOG (7.5p) and are paid export at 15p/kWh then, yes, ditch the diverter.

However if you have gas, you use that instead at 7.5p whenever you need hot water.

You can but that’s not very green. With a combi boiler it’s probably not too inefficient but if you have a traditional indirect hot water tank quite a bit of heat is wasted getting the water you want to use hot. 

Petriix

I think it's also mostly a myth (or wishful thinking) that self-consuming solar is 'greener' than burning gas. If you consider how the last bit of grid demand is met, burning gas at home is almost always greener than causing more demand on the electric grid. Exporting your solar usually does more good than not burning the equivalent amount of gas. It's optimal to minimise your demand and maximise your exports in most cases.