Advice on solar hot water systems in the UK? What do I need to know?

June 23, 2008 1:26 AM

Solar hot water and central heating for dummies? I'm in the UK, our (gas, combi) boiler has been rubbish since we moved in, and given that we're now looking at a new boiler we're thinking of complementing it with some sort of solar panel based solution. What should we look out for? What do we need? Can we reuse our existing radiators? What questions should we ask installation companies?

Caveats:

We don't currently have a tank, and we don't have much space for one (loft has been converted).
We need to get it done fast (expect current boiler will not last the month). Recommendations of suppliers to use and/or avoid welcome.

posted by handee to home & garden (7 comments total)

I can't recommend anyone based on experience, but I did look into this myself not so long ago and the main points I found were:

- I think you will need a tank, and also a new boiler that's compatible with a solar system (and go for a condensing one for efficiency)
- Evacuated solar tubes are the most efficient option

Did you watch 'It's not Easy Being Green' on TV the other year? They featured Navitron in the show and the book and they seem to have a good reputation. The site has heaps of information and will certainly tell you more of what you need to know. It seems more helpful and honest about outputs etc. than other sites and I imagine they will be helpful on the phone as well.

I have heard of quite a few companies really ripping people off, so do be careful despite your time pressure, and good luck - tell us all how it goes!
posted by dowcrag at 2:39 AM on June 23

Check out the INEBG forum. Lots of clever folk there to talk to about this topic.
posted by Solomon at 3:35 AM on June 23

I recommend you don't go solar. Get instantaneous gas instead. You won't need a tank, you'll never run out of water and you won't lose pressure if somebody uses the loo. The lack of a tank and the ability to precisely set water temperature makes them very energy efficient. If you don't have a lot of days of sunshine, you're probably going to need to use the booster a lot anyway, so you might as well go straight to gas anyway. Keep your existing gas radiators, and spend some of the money you would have spent on solar on better insulation and double glazing instead.
posted by obiwanwasabi at 4:37 AM on June 23 [1 favorite]

obiwanwasabi; we have double glazing and good insulation and are looking to replace an instantaneous gas system.
posted by handee at 4:38 AM on June 23

I don't know anything about the situation in the UK, but I can tell you that a popular setup in the states is to have a solar water heater upstream of an instantaneous heater. Thus, the instant heater only gets used if the water coming out of the solar heater isn't hot enough. From the standpoint of the user it is completely transparent, you get hot water all the time.
posted by LastOfHisKind at 5:21 AM on June 23

We looked into doing something similar last year, but couldn't quite afford it (and as we were about to start renting the house out, we wouldn't have seen the benefits in energy savings). I can't really recommend anything, but figured I'd add some of my observations...

Where would you be siting the solar panels? Our pitched house roof wasn't South-facing, so putting it on the garage roof (as that does face South) would've required planning permission.

Is there room in the bathroom (or elsewhere not in the loft) for a hot water cylinder? AIUI most of the systems only provide hot water, rather than full heating, and tend to use a hot water cylinder with two coils (one of the solar system, one connected to the GFCH as per a traditional system). I think the water tank in the loft is only needed for a vented cylinder, but you can get unvented cylinders with two coils which will give you mains pressure hot water and only need the cylinder (which usually wouldn't be in the loft).

As far as the Navitron tubes go, I did read a report a while back that reckoned that although they're more efficient, you generally didn't get any more useful energy out of them and so weren't worth the extra cost.

Finally, I did some thinking out loud about solar water heating on my blog a while back, including trying to work out some of the payback times, etc.
posted by amcewen at 5:46 AM on June 23

Evacuated tubes are the most efficient over a wide range of temperatures, but you may get better performance for your area out of the more traditional copper setup. It's also cheaper and less delicate.
posted by electroboy at 6:54 AM on June 23