Are people getting shot of solar water heating tubes?

Ubbquittious

Are they on the way out to be replaced by PV+immersion diverter which seems very inefficient?


Solar water heating still a viable option?

loyatemu

inefficient how?

I reckon we spend about 60c a day on hot water (using gas). So the maximum I could save a year with solar tubes is €220 but it's likely to be a lot less than that. Our electricity usage is about €700 a year, so getting even half of that from PV would be a greater saving. Payback obviously would depend on the relative costs of the systems but my understanding is long term maintenance costs are lower for PV.

Ubbquittious

loyatemu wrote: »

inefficient how?

I reckon we spend about 60c a day on hot water (using gas). So the maximum I could save a year with solar tubes is €220 but it's likely to be a lot less than that. Our electricity usage is about €700 a year, so getting even half of that from PV would be a greater saving. Payback obviously would depend on the relative costs of the systems but my understanding is long term maintenance costs are lower for PV.

The efficiency of using PV to heat water is capped at around 20% due to panel efficiency. I'm not sure what % the tubes are but would assume it's a lot more


You could save more if the tubes would also contribute to your central heating but I don't know if that type of setup is any way common over here. With the feed in tarriff soon dumping to immersion might not be as appealing anymore

KCross

Ubbquittious wrote: »

The efficiency of using PV to heat water is capped at around 20% due to panel efficiency. I'm not sure what % the tubes are but would assume it's a lot more

I dont know the exact efficiency figures but whatever they are I doubt they make up for the increased maintenance costs of the Solar thermal, which have pumps and glycol that have to be serviced/replaced.

There are no moving, serviceable parts in a PV system. It either works or it doesnt. The inverter is the short straw but should be good for 10-20 years and they are not expensive to replace.

Ubbquittious wrote: »

With the feed in tarriff soon dumping to immersion might not be as appealing anymore

Thats true too. If it costs 5c/kWh to heat your water (say with gas) and you can get 7c/kWh for sending your excess electricity back to the grid it doesnt make any sense to use the excess to heat your water as it will in effect be costing you money as you have to buy the diverter and lose the 2c/kWh difference as well.... all depends on what figures the FiT settle on, of course.

FYI: FiT is targeted to go live in Jul 2021. Thread on it here which is worth reading
https://www.boards.ie/vbulletin/showthread.php?t=2058149744

funkey_monkey

Ubbquittious wrote: »

With the feed in tarriff soon dumping to immersion might not be as appealing anymore

Would you not be as well just installing with that option and disabling it in case the rates change again in the future when you could enable it again?

loyatemu

Ubbquittious wrote: »

You could save more if the tubes would also contribute to your central heating but I don't know if that type of setup is any way common over here.

the savings would be minimal - you use your heating most at the times the sun is at it's weakest.