Just bought a new house and it needs a complete central heating overhaul.

Currrently it has a 30 year old system boiler with a vented hot water cylinder and all fed by Cold water storage cisterns in the loft. Central heating is micro bore pipe with standard rads.

The easy and cheap option is to convert to a Combi boiler which has the advantage of simple system, reasnoble low cost option, gain an upstairs cupboard and also a huge amount of loft space due to stupidly placed cisterns.

I like to think I am as Enviromental as possible and love the idea of solar water panels on the roof, so should I go for an unvented storage cylinder with a new system boiler. The roof slopes due South East so is possible with panels although not as efficient as due south.

My Questions are:

Is it worth using solar panels to heat water.
What is the ballpark cost of swapping an vented cylinder to an unvented.
How much would it cost in the future to add solar panels to a corectly speced cylinder.

Any general experience greatly received.

If it has any bearing the house is in East Devon.

Cheers Bigsurfer.

I believe it's one of the most cost effective eco-technologies with the shortest payback. If you need re-work it could work out very well for you.

However you'd better wait for one of our resident eco engineers to come along 🙂

My parents had some an reckoned the payback was between 10 and 20 yrs. However its a nice feeling to have hot water without burning fuel in summer

How long ago tho Teej?

Good point – 20 odd years ago. I guess the installations are cheaper relative to energy costs now.

And probably better/more efficient too.

From a site selling the stuff:

Although payback is one way of looking at the cost it is perhaps more accurate to look at the return on your investment that solar thermal offers. Typically the financial savings of a good solar thermal system will be equivalent to a tax free return on investment of between 8% and 12%.

I read an article on The Observer about this not too long ago. The general gist was that not only are solar panels a poor way of generating power in the UK but the concessions that the govt. are giving to have it installed are outweighing the payback to the economy making it actual economically unviable too. The only people to benefit are those who can afford to install it and reap the benefits of increased property values.
I'll see if I can find an online link to the article.

^^^

Well in that case get it done as quickly as possible before the government takes away the concessions!

As well as using solar for hot water have a look at using them for electricity also. The new government feed-in-tarifs which came in to play in April pay you an index linked amount per kWH generated elecy (guaranteed for the next 25 yrs). And if you have any surplus then you sell that back to the grid for extra £££.

http://www.energysavingtrust.org.uk/Generate-your-own-energy/Sell-your-own-energy/Feed-in-Tariff-Clean-Energy-Cashback-scheme

Photo-voltaic cells are even more efficient than solar panels for heating water. South facing roof is required, or as near to it as possbile, otherwise it is a waste of time and money. allthepies beat me to it – check out the energy saving trust website.

In terms of energy efficient refurbishment measures to your house, for energy efficiency the best thing you can do is insulate and draft proof.

Then fit a new efficient A+ rated boiler, radiators and TVRs.

Once you have fitted a new boiler, the payback on Solar Thermal panels won't be very good, because you're not saving very much fuel to fuel the water (already very efficienct) – although you will still save some energy. Conversely if you were fitting a solar thermal panel to an existing, less efficient boiler, it would be a better payback.

At this point you'd be better off with a solar panel for electricity, i.e. Photo Voltaics (PV). This will cost about £6k-8k but is now a good investment due to the newly introduced Feed-in-tariff mentioned above by allthepies. You can get something like 38p/kWhr for all electricity that you generate. Would getting a bank loan to do it, probably. And you will save significant amounts of carbon intensive electricity in the process.

For some more info see http://www.tzero.org.uk/About.aspx

Lots of insulation, draft proofing, better (thicker) double glazing all in hand.

I take wonny J's point about the payback period being much longer once a new efficient boiler is installed. Not to bothered about the payback period all good things are worth waiting for.

Will have to do some more research into costs and possible PV cells. I had discounted PV as I thought it wasn't worth the effort to generate such a small amount of energy.

If fitting a new condensing boiler then pre-heating the water may not be great as the boiler wont condense.

Not sure if the payback periods are finiancially worth it even considering feed-in tarrifs etc. Its more a question of whether you want to do your bit or not.

While not commenting on the Solar side of your question, I will say that I have had a vented system with an aged boiler system ripped out and replaced with an unvented cold water pressure fed, hot water system. This is absolutely fantastic and would recommend this over a combi boiler for all but the smallest of properties.

Except that the OP is asking how to spend money to make his house eco, he's asking that GIVEN that he is already replacing central heating, is it worth fitting solar?

Solar PV cells are in no way related to the project he is undertaking.

Solar panels will supply some of your hot water demands from taps but none of that needed by the central heating so it won't mean you no longer need to heat hot water. Not got any figures to hand but the payback seems to be in decades not years. Not looked at a DIY system but that might be better.

PV panels are OK due to the Feed in Tarrif but payback about 10 – 15 years depending on how you view certain things changing over time (eg electricity prices, interest rates). If you work out the figure don't forget to factor in how your capital would grow if not spent on PV panels. ie you have £10k. Invest over 10 years and it will grow at say 4%. Buy PV panels and you have zero in the bank but each year generate income of say £1k.

This will cost about £6k-8k

what size system is this for ?

Also just had a combi fitted and while it's OK (1 bath, three sinks in the house) I don't think I'd go for another one. Second getting the insulation, TRV and learning how to make best use of the system.

but none of that needed by the central heating

No? This company sell solar assisted central heating.

The same site quotes figures suggesting that you'd get 24% of your heating or hot water in January for free, and 90% in mid summer.

Cost of installing Solar Hot Water is about £4-5k. Make sure the system boiler cylinder you buy is compatible for solar hot water. Renewable Heat Incentive (RHI) if it happens, might provide a FIT style payback, but not until 2011 at the earliest.

I would still say the pv/FIT route is much better than the hot water panels, as you'll be able to make money on your installation (after a few years payback) rather than just slowly pay off the initial investment. Much quicker payback.

With solar thermal hot water, you will only save gas, on an already efficient system.

With solar PV you will save on electricity, which in carbon dioxide terms has approximately a 2.7 times greater carbon intensity than gas. Good for displacing the impact of any TVs, kettles or computers you might have.

Why does everyone talk about payback times for solar energy? they don't talk about payback times for a boiler or insulation, or do they?

To quote from that site….

Can solar thermal system heat my radiators?
Yes it can give you a % of heat to radiators but it is more suitable when installed with underfloor heating…..it is possible to heat you home by solar but it is unlikely that you would install the system because of
cost.

OK, so you could install underfloor heating to go with it but even then it's not cost efficient.

For pv a rule of thumb is £4k/kW installed. Although this a highly variable depending on what company quotes.

In terms of size, roughly 4m2/kW

People regularly talk about payback times for retrofit insulation.

And also for replacement boilers, but not for new ones.

But this isn't retrofit, the OP needs to replace the lot anyway.

I'd say call a company and get a quote, not listen to these weirdos 🙂

If you're not on mains gas, you could also consider as air source heat pump boiler. Even if you are on mains gas, going down this route could save you money by getting rid of your gas requirements & saving on the standing charges.

Would second the need to thermally improve & seal the house, & reducing the need for heating which conversely increases the percentage costs attributed to DHW production & back too solar panels.

Personally don't like combi's preferring un vented systems.

Actually I'd say PV costs more like £5-8/kW installed.

Molgrips, why is this not a retrofit project? If the house is already built then it is a retrofit or refurbishment.

"Even if you are on mains gas, going down this route could save you money by getting rid of your gas requirements & saving on the standing charges."

BS!

http://www.bsdlive.co.uk/story.asp?storycode=3142370

If it was an offgas property in Devon then I'd support an ASHP. But as they're on the gas network I'm not so sure.

Well ok but it needs doing anyway, so the payback times should be calculated on the cost of solar OVER the cost of a normal system… which should change it radically no? And PV is also not part of the equation.

I think the payback for Solar Hot Water fitted to an A+ rated boiler is pretty poor, like >20yrs.

http://hmccc.s3.amazonaws.com/21667%20CCC%20Report%20AW%20WEB.pdf
on page 173.

For more opinion I would recommend the forum on this site.

You will get much more impartial advice on that forum than you will get from speaking to any installers or sales people from a solar (or ASHP) company.

bigsurfer, have a look at these DIY systems from Navitron.

Navitron have an extremely good forum with lots of knowledgeable members.

I am in a similar situation to yourself and will be installing a solar heating system and new boiler.

PV systems are horribly expensive and very inefficient (something like 20%). Thermal systems are cheaper and can be about 90% efficient. They offer you the best bang per buck.

PV is great for reducing energy consumption but I didn't think that's what was being discussed here.

Go and speak to the Newbuilder forum people and the Navitron forum people.

Thanks for the Navitron link.

Lots more reading tonight then.

second looking at air source heating. if you use air source do not get solar as well as they are both solar technologies.

Lots of very interesting and useful information coming up here. Can I just suggest to the OP that if you do go down the unvented stored HW route that you have a circulated system installed. You will prob save more in water bills than in fuel bills. Also wasting water is really bad for the enviroment.

if you do go into the micro generation route you can earn money from it on the new feed in tariff scheme. I work for ecotricity who support it.

http://www.ecotricity.co.uk/for-your-home/microtricity

jakeclyro is right and hoodoo is wrong about paybacks. FITs turns the old financial model (hoodoo) on its head.

molgrips, I think the OP is interested in saving energy, that's why I suggested it. OP said, "I like to think I am as Enviromental as possible", which I took to mean saving energy and reducing carbon emissions.

Bear, air source heat pumps (ASHP) and solar systems actually make a good match. (it's not like the ASHP gets in the way of the panel, one is generally at ground level, the other is usually on the roof). With solar hot water, you can reduce the heat demand from the building and therefore the work the heat pump has to do. With PV you can provide some of the energy to run the pump. Neither of these however, addresses the fundamental problem with ASHP which is poor preformance in winter, when the external evaporator coils may freeze up. All a bit irrelevant as ASHP
is not a good choice for any property on mains gas.

matt_outandabout, dropoff and jakeclyro are talking sense.

Wonny – yes but an air source works most efficiently when the ambient temperature is higher (when the sun comes out and mainly in the summer) which bizarrely is also when solar panels work best (although there is a school of thought that says solar panels are not as good when they get too hot). So you are buying 2 technologies that work best in the same conditions, also in the summer you don't need your ASHP for heating but it will run hot water perfectly.

If you buy 2 systems payback will be far longer, if ever. If you are buying one and it works in your building buy ASHP as it offers far more than just hot water. Also some interesting new figures being talked about for grants for homeowners for them, not sure if they will get the go ahead but if they do then it becomes a no brainer.