Are Thermal Hot Water Systems Worth It?

Just had a guy round (collared wife at tesco) to see about installing PV, know idea why she invited him round knowing we cannot really have it. Had someone else before and our roof simply isn't big enough. Anyway, he got on about solar thermal for hot water. Works with combi he says, saves you loads he says. He recons 40% saving on gas bill (about £300 per year for us). Plus he says we get paid for it via Renewable Heat Incentive from april when it is introduced (recons £300 plus).

Says £3500 for install, they setup a 10 year payment plan which would cost £46 per month. So IF the system does what he says (300 + 300) = £600 per year. divide that by 12 months = £50. minus the 46 leave £4 per month gain. Not a great deal to be honest. Then this RHI is only for 7 years, so the last 3 years actually cost me. And all this is IF the system does what he says. I've tried doing some research but cannot find much. but everything I have read says these systems can save around £150 per year in gas (this is not the £300 he reckoned). Lastly, be the sound of it, the system will likely be knackered by the time the 10 years is up so I won't reap many benefits after that.

So, am I seeing all this in the right light? Anybody have anything to add? positive or negative.

Thanks

How can it work with a combi?

Solar thermal requires a hot water tank that has a solar input coil at the bottom (in addition to the input coil from the boiler)

So it won't work without a hot water tank, and if you have a hot water tank you don't need a combi.

Solar PV is better. you get paid for the electricity, and you can install an immersun or similar to dump all surplus solar PV into the immersion heater.

As a combi boiler is normally hot water taps supplied from street water pressure same as cold taps and tank stored hot water, (as the solar thermal would create), would be gravity fed pressure, I'm not sure how you are going to get this dual pressure source to your hot taps. As with all forms of solar energy you have to consider how much of the energy you generate can you use, can any surplus be stored for later or can you can gain revenue from any surplus. Every home is an individual case that needs to evaluate the real requirements of what they are actually consuming first of all. I don't think many of these sales reps can do that sort of evaluation. They just have sample figures that may only apply to a select percentage of the population.

Doc H.

ProDave said:

How can it work with a combi?

Solar thermal requires a hot water tank that has a solar input coil at the bottom (in addition to the input coil from the boiler)

So it won't work without a hot water tank, and if you have a hot water tank you don't need a combi.

Solar PV is better. you get paid for the electricity, and you can install an immersun or similar to dump all surplus solar PV into the immersion heater.

Click to expand...

Basically, the collectors heat a tank (250l)  of water. the water drawn off that goes to a smart diverter valve of some sort. if the water is > 60 degrees C it goes straight to taps, if it is lower then it goes to combi which heats it further then to taps.

Load of ballcocks, 

The average house is unsuitable for solar thermal, and the fact you have a combi makes it worse.

Was the salesman a former double glazing man?!

Sharpend said:

Was the salesman a former double glazing man?!

Click to expand...

Upon looking into it, they do all sorts..... including double glazing :innocent

Doc Hudson said:

As a combi boiler is normally hot water taps supplied from street water pressure same as cold taps and tank stored hot water, (as the solar thermal would create), would be gravity fed pressure, I'm not sure how you are going to get this dual pressure source to your hot taps. As with all forms of solar energy you have to consider how much of the energy you generate can you use, can any surplus be stored for later or can you can gain revenue from any surplus. Every home is an individual case that needs to evaluate the real requirements of what they are actually consuming first of all. I don't think many of these sales reps can do that sort of evaluation. They just have sample figures that may only apply to a select percentage of the population.

Doc H.

Click to expand...

The new tank would be pressurised.

I'd say a heat pump would be a far better investment.

If I had the money, and a cylinder that would be my choice. 

Ive been involved in a conversion of an oil fired combi to work with solar... they basically blank off the HW from the combi and then S plan the heating and HW

Then there were two tank stats iirc

http://www.energywiseuk.co.uk/thermodynamics/

These are the emerging tech - a sort of hybrid between ASHP and solar thermal.

I`ve got a colleague who does AC and refrigeration looking into the viability........... But seems like a good thing - if it does what it says on the tin......

Barx said:

Says £3500 for install, they setup a 10 year payment plan which would cost £46 per month.

So, am I seeing all this in the right light? Anybody have anything to add? positive or negative.

Thanks

Click to expand...

Further thoughts on this re the payment structure, Is this a loan or a form of rental agreement? I heard an article on the radio this week about someone who was having problems selling their house because of a rental type agreement with a solar PV system that was installed a few years ago. They had a new buyer already to sign up & exchange contracts etc but there were complications transferring the contract for the solar PV system which basically blocked the sale they were hoping for. Do you intend staying at your home for the duration of this agreement? 

Doc H.

It wasn't a rental system, I think they are for when companies give you systems for free?? they rent your roof for the 25 years. This was a Home Improvement loan I think.

kme said:

http://www.energywiseuk.co.uk/thermodynamics/

These are the emerging tech - a sort of hybrid between ASHP and solar thermal.

I`ve got a colleague who does AC and refrigeration looking into the viability........... But seems like a good thing - if it does what it says on the tin......

Click to expand...

that more or less describes most of the ASHPs Ive installed, and how they work,

it is deffo a viable system if installed correctly, and very good IMHO.

and I think, much more efficient than merely blowing warm air systems.