Solar thermal – worth installing?

Need to change our hot water tank as part of new boiler install. Is it worth getting a tank with an additional /spare coil for potential solar thermal in the future? Located in northern scotland, got a south east facing roof which I’m guessing would be suitable for panels, probably a 250l tank (family of 4), maybe 300? Will be tied into the new gas system boiler.

Read a few posts from many years back with mixed views on it. Any updated thoughts, advice or things to look at?

I’ve got a spare bit on mine for this, got one with three. One for the back-boiler on the stove, one for the immersion, one for future solar thermal. Barely cost any more than one with two.
Just because it’s there doesn’t mean you have to use it but it keeps your options open.
.
My electricity bill of £10-12/month doesn’t warrent shelling out on the solar thermal but I have the option if I need to with a bit less faff than it would otherwise be.

I have been looking in to this with the new grant. I’ve had one quote back that is astronomical. I wanted it to stop our reliance on oil.

Chatting to a handful of renewable installers, most have said they no longer offer thermal as its far more costly and not as popular now. It also requires more maintenance what with having pumps etc.

All have said that PV is better. As cost to install is less, far far less maintenance than thermal plus it can also heat hot water. Getting a few quotes now to see the cost difference.

Do it quickly and you can still claim the generous RHI subsidy.

https://www.ofgem.gov.uk/environmental-programmes/domestic-rhi/applicants

My parents have it.

Their backup is a massive calor gas tank in the garden. It rarely gets used.

I have been considering this. Seems like a better modern version of night storage heaters, but heating up in the day just before you need it. PV does seem the easy option but I’ve not got much further than pondering yet.

My parents have it and it works well in the summer for hot water.

I am personally about 2/3 to 3/4 through doing my own C/H with multiple power sources system (all DIY) and have a spare coil for solar thermal, but I don’t think I will use it, more likely to get some PV panels and link into immersion heater. They are a good system and If I had a larger thermal store I may consider it but there is a bit of maintenance involved replacing glycol and doing a flush, re-pressurising , (if anyone want details on a homemade rig to do this message me) and it more running of pipe etc compared to cables.

Energy per M2 I *think* they are better than p.v. me, if being installed as part of a new system may still be worth it but compare costs to adding p.v. with the power being dumped via and immersion heater. (Take into consideration your lattitue for expected generation).

Note this is from a DIY perspective so install costs are not included here. My negativity is also clouded by no wanting more work!

I put solar thermal into our last place. We had a large thermal store (370l) with feeds from the oil boiler, multi fuel boiler stove, and the solar thermal panels. It worked well on a south facing roof in Highland Perthshire.
I’m not sure it saved us any money though.
The current place has mains gas so I’ve not bothered.

Their backup is a massive calor gas tank in the garden. It rarely gets used

If it’s installed as most are via some form of heat bank / thermal store you probably wouldn’t notice when it’s working or not. Even if it doesn’t get the water to full temp it may well do a lot of work to get the water to 90% of what you want / need.

Edit: may have read you post the wrong way round?

OP is that a new hot water tanks (Venter or in vented?) Or a thermal store (Which can also be vented or unvented but usually vented in the UK)?

OP – hot water tank manufacturer here – have PM’d you.

Do it quickly and you can still claim the generous RHI subsidy.

slight threadjack – are any of these schemes covered by RHI and/or the Covid voucher thingy AND actually worth doing financially (given that we intend to stay in our property long term)? What about ground source heat pump? Would really like PV but doesn’t seem to be covered under any decent scheme currently so probably doesn’t add up.

Zilog I am by no means an expert but I put our details into the Covid scheme and both solar thermal and PV seemed to be covered with quite a few local installers. I was after solar thermal but now thinking that solar PV might be the better option. I don’t as yet know what the real world savings could be though.

I think that PV has it beat in most circumstances:

ST is a one-trick pony but can produce a lot of hot water in the better months although it’s kinda involved. Pumps and pipework in the roofspace add to the risk of “issues” and the pump takes energy to run. Excess heat also has to be dumped I believe so there’s some planning/hardware involved there.

PV on the other hand is ‘dry’ and can run a multitude of electrical items and heat your water.

Thankfully we got in very early in the FIT scheme and it ‘earns’ us £1800/year

Zilog I am by no means an expert but I put our details into the Covid scheme and both solar thermal and PV seemed to be covered with quite a few local installers.

@bigsurfer what website are you using? Everything I’ve read says that PV isn’t included as either a primary or secondary measure under the scheme. If I take the survey at simpleenergyadvice.org.uk then it recommends PV as an energy-saving option, but one that I’d have to self-fund.

Zilog you are correct it looks like Solar PV is self funding which puts it out for us. Might still look into Solar thermal as we need a new hot water cylinder ideally unvented anyway.

I’ve had one for over ten years. Designed and built it myself including the panel itself after lots of research and poking around friends’ instalations. We live 43°N so it works better than it would in the UK

Objectives
No power or maintenance needed: so I put the tank as high as posible in the roof, the panel panel low on the roof and used 18mm pipes throughout. It thermosyphons fine.

Low heat loss: So I made the panel out of the biggest Velux double glazed window I could buy locally (non-treated glass) and built it into the roof with R5 insulation all around it. All the pipes are double lagged and the tank is wrapped in multi-layer insulation. The matrix is designed to flow freely and be air-lock free. It has a lot of copper pipe and plate in it – the more surface of copper exposed to the sun the better.

Make the most of the panel in Winter: so I use the solar sytem as a pre-heater before a conventional electric tank, when the solar heated water isn’t hot enough for a shower I turn a couple of valves and it’s routed through the extra tank.

How much hot water does it produce ?

Lots. Enough for six months of the year and a significant contribution for another three, in December the water is no better than tepid but that still means the electric tank has less work to do. We fill the washihg machine direct on the fill cycle so today it’s provided two washes, a couple of piping hot showers and domestic hot water.

Problems ?

I have to remove the lagging from a pipe run before going away for more than couple of days in Summer or the primary circuit boils.

The panel needs cleaning in the Spring and Autumn – doing so gains an extra couple of weeks compared with leaving it dirty. It gets a lot dirtier than the “self-cleaning” glass of my PV panels.

Training the family to use it – valves need turning when the washing machine is used, and other valves need turning when the electric tank is needed to add a few degrees. When the electric tank is being used four valves need turning to revert to solar only for the washing machine.

I installed a 20 tube array on my roof facing west, it cost me about £700 including a 160 litre cylinder off eBay, which I plumbed in tandem with the existing cylinder, right above it in the attic. I seem to have got a good balance between collection and debit through the coil, in summer the tiny 12v pump runs almost continuously and occasionally will heat the entire 160 litres to 60c, meaning the gas boiler does almost no work at all. I haven’t done the sums but I reckon it paid for itself after 7 years. It’s not spectacular but there’s a lot of satisfaction in knowing that long hot shower is almost free, water being so cheap.

Yup I have one and it provides all my hot water during summer. My woodburner provides it all in the winter, so my gas boiler does as little as possible.

Current gas bill is £5 a month.

Long story short and trying to keep it fairly simple, i’m looking at combining two systems, incorporating an annex into the main house. Currently have a gas boiler with a vented system that provides the central heating throughout both and got water to main house. Boiler is old and is due to be replaced imminently. There’s a second hot water tank that is electrically heated for the annex.

Looking at a new unvented system boiler to a new single tank that will cover the heatimg and water for both all from the gas.

Guess it makes sense to add the second coil at this stage if it doesnt cost much more. Gives the option to add solar thermal later, if not then not significant outlay. Assume savings compared to gas not as good compared to oil/elec therefore longer payback period for any investment but don’t know what sort of factor of difference?

Hadn’t thought on PV, can that just tie direct into immersa element or does it generally back feed into the grid?

Had wondered about the covid grant scheme but doesn’t cover Scotland as far as I’m aware….??

With PV you fit am immersun type box which routes spare generation (i.e. Anything the house isn’t using) into the immersion.
When the water is hot it then routes the power to a second outlet e which can be almost any electric heating system – so another immersion, electric underfloor, towel rail, panel heater, etc.

Should be cheaper too as you don’t need the mgs bollocks.