Solar Power for the Home

[TheAnimus]

Ok, so a quick bit of background, my parents are retired, my mums health was declining rapidly and so they retired a bit sooner than originally planned, and I think as such it takes a toll on their sanity.

They live in a truly stupid place to live, Cornwall. Cornwall is actually getting more expensive and less pleasant to live with every passing day of energy price rises, its becoming quite apparent that they simply can't afford to run the Agar any more, with the increased price of heating oil. As they are not on mans gas, that too is also very expensive for heating the home. The water bills also keep rising. The sparse rural community can not simply have all the luxuries of the condensed efficient cities without a significant price difference.

As such, I thought that some form of geothermal heat pump would be a good way of delivering cost savings on heating the house. With grants available because of the stupid bunny huggers, I told them I'd pay for it to be installed if it looked worthwhile, after having someone look at their property, they have been advised to look at PV solar panels.

Now I've lived in Cornwall for enough years for this to make me think "really?!" I mean I joke cornwall has but two seasons, The Rain and Dizzel season, and the Drizzel and Rain season. I thought that a 4MW set of panels wouldn't really work very well, the firm agreed with my educated guess of 20% at best. However what I didn't know is quite how insane the subsidies are.

Apparently you can sell it back to the electricity firm for 43.3 pence per KW/h! For the next 25 years (inline with RPI)

So have any hexites done this? My motivations are purely efficiency on someone living in some place as inefficient as cornwall (don't get me started on broadband subsidies and the looming issue of travel subsidies). The cost savings look to be quite substantial especially if they continue to use heating oil as their primary fuel source, whilst selling back the energy to the grid.

My immediate concern is how the electricity firms 'net off' the subsidised price. If it turns out you use 20 units a day, and generate only 5 units, and the firms decide simply to reduce your bill by the cost of 5 units at normal rates of say 5 pence per unit, then the 25p per day saving will never pay for the cost of the panels.

[aidanjt]

Your parents must have a *lot* of empty land available if you're aiming for 4 megawatts capacity.

Solar radiance works out at 1kW per square metre on a perfectly clear day, directly below the Sun. PV cells at best trap 50% of that as energy. A further 4-12% is lost in DC->AC conversion. So that means you'll need about 6 square metres just to put on the kettle, on a perfectly clear day, in the Sahara.

The cells will also have to be maintained, cleaned regularly, they're fragile and will need replaced if broken. They'll also be weathered by acidic rain, wind, ice formation, etc., and gradually lose their effectiveness as a result.

Solar makes sense in Spain or Africa or some place where pure sunlight exposure is practically constant, and you can net a return in a few years. It doesn't make a lot of sense in the gloomy Isles where direct sunlight is a rarity, and spread over a greater distance even when it isn't.

[TheAnimus]

lol MW was a typo, I ment kW!

But in Cornwall it is rare to get snow and ice, also the firms are willing to guarantee the panels for 15 years, and 10 years for the inverter. In my spreadsheet I'd put the inverter at 80% efficient. So I'm not too worried about that, its just how much light the panels will actually get. There are firms who survey these things but they aren't regulated really, and unlike when you say buy a mortgage with the bank worrying about 50%+ of the value drop due to a bad survey these guys won't go near underwriting the validity of them. That scares me.

[Lanky123]

I thought that a 4MW set of panels wouldn't really work very well

Sorry, 4 Megawatts!? I would hazard a guess that you mean kilowatts but I think even that would be quite a large domestic installation? *Edit...aidanjt beat me to it.

So have any hexites done this?

My parents have done exactly this. They had 12 panels with a total 2.76kW (peak) capacity placed on the nearly South facing roof of the house. The installation cost just over £10k and the estimated savings/earnings per year are around £1k (that's assuming electricity price increases and inflation to be zero). The panels have a performance warranty for 25 years.

It was about a year ago that I looked at the numbers but if you have the cash spare and a roof pointing in the right direction the (admittedly obscene) subsidies do make it worthwhile. Before anyone gets any bright ideas (not a pun, I promise ) I should probably point out that there are limits on what counts as a domestic installation...you can't get subsidised in this way for covering a farm or something in PV cells.

[malfunction]

Are thermal collectors (i.e. solar panels that heat water rather than generate electricity) an option in this country?

[TheAnimus]

My parents have done exactly this. They had 12 panels with a total 2.76kW (peak) capacity placed on the nearly South facing roof of the house. The installation cost just over £10k and the estimated savings/earnings per year are around £1k (that's assuming electricity price increases and inflation to be zero). The panels have a performance warranty for 25 years.

That sounds very similar to what my parents are looking at, with a 4kW peak capacity (yes, its super humiliating I made such a stupid slip on units!), they are been quoted in the range of price around 14-16k for installation of everything.

Do you mind my asking were your parents live, and what yield they are seeing on their panels.

[Lanky123]

That sounds very similar to what my parents are looking at, with a 4kW peak capacity (yes, its super humiliating I made such a stupid slip on units!), they are been quoted in the range of price around 14-16k for installation of everything.

Do you mind my asking were your parents live, and what yield they are seeing on their panels.

My parents live in Swindon which isn't too bad in terms of the weather but it's still Britain if you see what I mean. I'm sure you can find average weather statistics somwhere on the internet.

The panels were installed about a year ago and the general impression I've got is that they've lived up to expectations so far. I'm sure they'd be quite happy to divulge some numbers but it might take a day or two to get back.

[peterb]

IIRC (and I haven't done the sums) the installation cost is around £5K/KW. You get use of the electicity you generate, you can sell excess back and you get 43p ayway per unit generated. The panels are supposed to last 25 years, although they lose efficiency with time. The experts (and I havn't included links because I ca't remember where I read it) seem to think that the payback period is about 10 years (although with energy costs rising that may shorten - but you also have the reduction in effciency to factor in)

I have seen another scheme where you rent your roof to a company, installation costs £99 and you get free use of the power you generate, but the sales and subsidy go to the company that is leasing your roof space.

Less profitable if you are going to be living in the house for a long time, better if you might be moving in less than ten years, and very low initial investment. Payback is therefore quicker.

Quite a major investment, so pays to do a lot of research!

[Lanky123]

Do you mind my asking were your parents live, and what yield they are seeing on their panels.

Ok, over the first 12 months since installation they've generated about 2700kWh total. The maximum for a bright, sunny day is about 16kWh. Again, the panels have a 2.76kW peak capacity and are on a SSE facing roof at a tilt of 30 degrees. A little more info on the warranty - mechanical warranty for 5 years, performance warranty for 12 years at 90% rated output power and 25 years at 80%.

Rough averages over the course of the year (my dad's a statistician, apparently he had all this stuff in a spreadsheet anyway):

[MaddAussie]

My Landlady has a wodge of the buggers on the roof, had them since april, i'll get the figures off the doohicky in the livingroom tonight

[circuitmonkey]

Are thermal collectors (i.e. solar panels that heat water rather than generate electricity) an option in this country?

My parents have been using them in the swindon area for about 2 years, they work very well. I don't have exact figures for you, but they have 4 panels and it produces enough hot water for the whole day (although the CH isn't in this loop).

The only down side to the project where the cowboys who put the system in, but the German who flew over to commission the system managed to fix all there f*ck-ups

[Saracen]

My neighbours have done this, and their figures to date are encouraging, to the point that I've been thinking of it, because and only because of the feed-in tariffs. As I understand their deal, they get paid for every unit they generate, including what they use, and they get paid an additional sum for every unit that gets grid back to the grid. So the get benefit from :-

a) generation
b) supply to grid
c) not having to pay electricity company prices for what they use
d) optionally, using surplus electric to cut gas usage for hot water and, if applicable, cooking.

The downsides, clearly, are the substantial up-fro9int capital costs (unless you use the "rental" option, and the cost implication after hardware guarantees run out.

A slightly less overt point, but one that'd central to me, is .... what effect on property value if you move?

If you're planning on being in a house long-term, that's not relevant. But I'm not. So, if I indulge in, say, £12,000 of investment now, and then move in a year, will the installation increase the property value. In theory, it ought to, as the income then goes to the new owner, but in reality, does it? And will it make the property harder to sell, if you've got to convince the new owner to adopt the capital risk, by paying a higher price for the property, on the promise of the income from the "investment". In other words, if I sell, I've got to convince the new buyer to "invest" in the idea, too. And I'm not convinced how easy that will be.

So, regardless of feed-in tariffs, if I do it while planning a move in a year (or three), I'm making a bet on the effect on property value. I'm nor sure that's a bet I want to make. Other than that, the arguments in favour are, IMHO, pretty strong.