Solar PV and thermal or just PV?

cjgrey

Hi

I've got about 25m2 of south-west facing roof and I was thinking of putting solar panels in. What I haven't been able to understand is how to decide what is the best use of roof area, given the new FIT's for solar PV and the upcoming scheme for thermal - should you have both PV and thermal, or are you better off to just have PV? For example, in my case, would I be best to have say 5m2 of thermal and 20m2 of PV, or use the whole 25m2 for PV? I've seen lots of payback calculations for thermal and PV but none that compare the two, given that the limiting factor is how much roof area you've got available.



I'm interested in understanding what's best both from the green and the financial side, but on the financial side, I understand that the tariffs are calculated at 12% for PV but only 6% for thermal so does that suggest that you'd be better off with PV only?

Thanks in advance!

Catherine

noncom_2

My understanding was that all the Govt schemes have been calculated to give something like an 8% return (currently tax free) over the long term. I've not seen evidence that Solar PV gives a genuine 12% return (don't believe the figures you see from the companies trying to sell you the systems).....

I know lots of people have strong opinions on both the systems you mention, but from what I've read it seems to be generally held that Solar PV systems are more use than Solar Hot Water systems.

Personally I would think it makes more sense to choose one system and fit the biggest one you can to your roof. Having both will increase your installation cost, and also the cost per unit of "power" (be it electricity or hot water) generated goes down as the system size goes up, so having two small systems will be much more expensive than one large one.

If you chose to fit Solar PV, then you could consider using something like the EMMA device (mentioned in an earlier thread) which will monitor your generation and whenever you are making more electricity than you are consuming in the house it will divert that surplus power to a specific circuit, which could be for example an immersion coil in your hot water tank (giving you free water heating from the PV panels). I have not found out detailed information about the product, and am not at all convinved that it would prove cost effective in the long term, but it is a possibility to consider. Alternatively you could monitor your generation from the smart meter data for a year, say, and then work out when you can safely use a timeswitch to operate the immersion during the daytime, being relatively confident that the electricity will be "free".

albyota

If we were in the south of France or Spain you would be wise to do both, however, in the UK we get very few warm sunny weeks/year where the solar thermal would yield very much (possibly 60p worth of 'free' hot water/day for 50 -60 days). whereas, with Solar PV, it would be generating 365 days of daylight, albeit, on dark cloudy days the yield would be lower. Solar PV at 41.3p/kwh for 25 years, index linked, tax free. against Solar thermal at 18p/kwh 'deemed' tarrif for 18 years.

cjgrey

Hi noncom & albyota

Thanks a lot - that seems sensible to me. It's pretty much what I was ezpecting, except that I couldn't find any numbers to compare directly and also lots of people have thermal and seem very happy with it!

Catherine

Cardew

cjgrey wrote: »

Hi noncom & albyota

Thanks a lot - that seems sensible to me. It's pretty much what I was ezpecting, except that I couldn't find any numbers to compare directly and also lots of people have thermal and seem very happy with it!

Catherine

Agree with albyota! No contest - solar PV.

If you examine the results of Solar Thermal - and there are Government tests on systems - you will get about 1,000kWh per year out of an average system; say £30 a year if you have gas(before any Government subsidy) Even with the very best systems you get virtually no Hot water in winter(a few kWh)

The reason many people say they are happy with thermal is cos they have paid £thousands and don't want to face reality!!

Ask any Trading Standards Office about solar thermal if you want some facts.

daytona600_2

solar pv is the best
very good earnings and tax free and index linked
will last decades - thermal has many problems

but you can get combined pv and thermal systems these days
PV-T still untried technolgy



I've got about 25m2 of south-west facing roof and I was thinking of putting solar panels in. What I haven't been able to understand is how to decide what is the best use of roof area, given the new FIT's for solar PV and the upcoming scheme for thermal - should you have both PV and thermal, or are you better off to just have PV? For example, in my case, would I be best to have say 5m2 of thermal and 20m2 of PV, or use the whole 25m2 for PV? I've seen lots of payback calculations for thermal and PV but none that compare the two, given that the limiting factor is how much roof area you've got available.



I'm interested in understanding what's best both from the green and the financial side, but on the financial side, I understand that the tariffs are calculated at 12% for PV but only 6% for thermal so does that suggest that you'd be better off with PV only?

Thanks in advance!

Catherine[/QUOTE]

craftymummy_2

You may be better waiting a few months before installing solar thermal as solar thermal and heat pumps will have a feed in tariff starting April 2011 which as long as the equipment is MCS approved and installed by an MCS contractor will qualify for the 20 year FIT rate.
The rates proposed should return a cheque to the customer of around £200-£250 per year , every year fixed for twenty years which is around £4K.

MCS solar equipment is solarkeymarked .

I know this because my husband is MCS approved for solar PV , solar thermal and heat pumps and also an approved Ecodan installer.