Solar for hot water - best option for retrofitting

batman1

Hi,

Looking into a renovation and hoping to fit solar for hot water. Reading through the forum there are lots of differing views and details. I am hoping someone can indicate the best direction to go with the ever-changing technology and system improvements etc.

Existing system is as follows :
Oil heating (rarely used) and stove with boiler. Immersion for summer hot water. 'Standard' small hot water tank, factory insulated. (copper one)
No heating controls. House is small dormer semi-d ~ 1350sqft.

We would like to install a solar panel for hot water as we are constantly using the immersion, especially in summer. 2 Kids getting bigger and using more hot water etc. We have 1 gravity shower running from the tank, 1 electric shower and a bath (never used).

Should we be looking at a set of 30 tubes, as not much more would fit on the front of the roof, or the heat pump type (thermodynamic?), which is smaller?

I am aware that the heat pump type is based on electrical use unlike the tubes. Costs appear to be similar for installing.

I explored getting companies to come and survey but am reluctant to be pressured into going for a brand based on sales reps 'promising the earth'.

Any advice is much appreciated

quentingargan

I'd also look at PV as a third way of heating water... When PV was more expensive, it wasn't an option, but the price of modules has fallen dramatically in recent times.

Solar turbes require maintenance - you need to change the antifreeze every two years. The system will also have occasional failures of pump station, expansion vessels etc. So its not completely free. By comparison, PV is solid state with no water, moving parts or other component failures. The panels have production guarantees for 25 years, and the only part which may fail during the system lifetime is the inverter (which anyone can easily swap out as they are plug-and-play).

As an example, a 2kw PV system will cost about €2500 for the hardware, and will, on a south facing roof, produce about 1900 KwHrs per year.

You can get a device (see here ) which diverts surplus energy to hot water. These devices cost from €250 to €450. (ex-VAT )

If you use ¼ of this in the household, and use the remainder to heat water, it will save you 18c / kw Hr for the electricity used, and in your case, much the same for the hot water saved. A 4m2 solar thermal system will produce about 1800 Kwhrs of hot water.

The big difference is that the maintenance is zero, but the initial cost may be slightly higher. The roof area taken up will also be a lot larger. You don't need to change your cylinder as the diversion works with your existing immersion heater. Another difference is that when you're away on holidays, the system never boils - it just puts the surplus electricity onto the grid for free.

batman1

Roof space is an issue so I am looking at the most efficient solar hot water system. There are lts of options and brands, each saying they are better than the next.

If I had the space I would consider PV but that is not an option.