Where it all began

This is my blog about our solar panels.  I first looked into solar panels about 3 years ago when the UK feed-in tariff was launched. Back then, the householders who generated their own electricity were earning 41.3p per kWh (solar or wind).  Sticking a thumping great turbine up at the bottom of the garden would not have helped our good relationship with our neighbours, and besides would certainly not have received planning permission, so that left us with solar.  I asked for a quote from a local specialist, and it came back at 'about £15,000'. We didn't have that kind of cash, so I reluctantly had to let it go.

A few months ago, I decided to look into it again. The government are now offering a feed-in tariff of 14.9p/kWh for installations that are commissioned before October 2013 (http://www.energysavingtrust.org.uk/Generating-energy/Getting-money-back/Feed-In-Tariffs-scheme-FITs#rates)

• A little aside about the feed-in tariff system:  You have an electricity meter installed with your system that measures just the electricity you generate from the panels. You get paid (by whichever energy company supplies your electricity) for every kWh your system generates. The early adopters are still getting 41.3p for their electricity - and will continue to get that until their tariff expires. Each feed in tariff runs for 20 years from date of commission. The price you earn is 'locked in' from day 1 of your tariff. So we'll fall into the pre-October 2013 tariff, which means we'll get 14.9p for every kWh we generate from now until 2033.  Another important note is that since 2012, the government have introduced a restriction to feed in tariffs - to be eligible for the full rate (14.9p currently) your house must have an Energy Performance Certificate (EPC) of at least band D.

But what's a kWh and a kW?
Every panel generates a certain amount of kW (kilowatts). Usually 1/4kW each. If you have 4 panels, then your system will generate 4 x 1/4 = 1kW. If you have 8 panels, then your system will generate 8 x 1/4kW = 2kW.  These values are the absolute maximum power they can generate, in full, direct sunshine. Overcast days or panels in shade will generate less than this. Obviously, at night time, they generate nothing at all (duh).

But you don't get paid for kW, you get paid for kWh (kilowatt-hours). The longer you leave them 'turned on', the more kWh they generate. If you leave a 2kW system running for an hour, it will generate 2kWh. If you leave a 2kW system running for two hours, it will generate 4kWh. Leave it running for 3 hours, 6kWh, and so on and so forth.  Remember, these are maximum values - you will not get the maximum out of your panels from sun-up to sun-down (more on that below - see prediction calculators).

14.9p per kWh? But you're getting so little compared to the early adopters?
Yes we are. But, 3 years down the line, solar panel technology has rapidly developed, with 3rd generation ("HIT") panels now available for a lot less than the 1st generation panels. For the same amount of sunlight, each of my panels (http://www.evoenergy.co.uk/wp-content/uploads/2012/05/Datasheet-HIT-240W.pdf) will generate about 1/3 more electricity than the panels I could have bought 3 years ago. And they're smaller, so I can fit 8 of them where I could only fit 6 of the 1st gen panels. Another point to note is that all solar panels degrade over time. Even the 3rd gen panels are quoted as generating only 80% of their original power after 20 years (90% after 10 years).

Prediction calculators.
There are a number of online forecast calculators (eg http://www.energysavingtrust.org.uk/Generating-energy/Getting-money-back/Solar-Energy-Calculator) that will predict how much energy (kWh) per year you are likely to generate. They take into account things like: how many kW of panels you're putting up;  the direction your roof points; how long the sun is in the sky each day; where abouts you are in the UK (southern homes will get more sunlight than northern homes and so therefore generate more electricity); the angle your roof is at (about 30-40 degrees is the optimum angle so I believe - panels laid flat or vertically generate less, something to do with reflectivity).  Our rig has been predicted at 1645kWh per year using the above calculator.  I've chatted with two solar panel installers, and both told me that every single installation they have put in has generated more than the predicted amount. But they are not allowed to give a more accurate estimation, they have to use the gov't figures. They added that it's better to get a pleasant surprise than be disappointed!

I found a company online called the Low Carbon Energy Company.  They've been installing solar panels for about 15 years, they're MCS registered (Micro Generation Certification Scheme) which means they're approved for commissioning the installation for the feed-in tariff (essential).  I was quoted £5270, all in, to install the system (8 panels - 2kW) and commission it.  Where do I sign, I said (after checking with the wife and the savings account, naturally.)

Financial aspect
From an investment point of view, using the official generation prediction, we'll be generating 1645 kWh x 14.9p per year. This is £245 per year, which equates to a 4 1/2 % return on the investment, worse case scenario. You'll struggle to find 2% on even a locked-in deposit account so it makes great sense from a purely financial point of view. But it doesn't end there. I am perfectly entitled to use the electricity I am generating. I still get paid for every kWh I generate, even if I use it all myself. The only proviso being that it has to be used as it is being generated, ie, during daylight. But it doesn't end there. The government assumes I am going to use half of the solar generated energy myself, and I get paid again at 4.64p per kWh for the remaining half I'm sending back to the grid. Which is another £38 per year. A pittance, but still.

I work from home, and my office has 3 computers, 21 downlighters and an air con. The dishwasher and washing machine are in regular use during the day. I don't know how much of the solar generated energy I will use, but it'll be a large portion of it.  All my home-grown energy I'm using is energy I'm not having to buy from the grid. So I'm making a saving on my electricity in addition to the money I'm being paid from the feed-in tariff. If I estimate that I am using half the energy I'm generating, that equates to 822.5 kWh per year. I'm paying 15.1p per kWh for my electricity at the moment, so that is a yearly saving of £124. So we'll be better off to the tune of £245 (f.i.t.) + £38 + £124 = £407 a year.  This gives a total time to repay the £5270 investment of just under 13 years, so it's a long term investment. However, I'm cautiously optimistic that the actual figures will be a lot better than these, but only time and the sunshine will tell. In addition, as electricity prices go up (and you can bet your bottom dollar they will), the savings we're making will increase.

We're in the fortunate situation that the back of our house faces due south, which is ideal for solar panels, because they're collecting direct sunlight all day long.  From the conversations I've had with installers and proponents of the industry, you can put solar panels on west- or east- facing roofs, but they will only generate significant amounts of power in the morning or evening.  That doesn't mean you can't put solar panels on east or west facing roofs, but they won't provide as high a return. North facing roofs are not worth the bother.

Rear of our house with the scaff up ready to install. Half a day's work for three scaff men. Would have been quicker but they had to do a bridge over the conservatory.

The complicating factor
Our house has an original roof - this means that when the tiles were laid back in the 1930s, they were laid directly onto the wooden roof battens, without a layer of felt between the two (as they do nowadays).  The previous owners of the house, in their infinite wisdom, decided to insulate the loft on the underside of the roof with that spray on insulation foam stuff that sets hard (looks a bit like cinder toffee).  Because it was sprayed directly onto the underside of the tiles, it welded them all together, absolutely welded them. When the roofers came to examine the roof, every time they tried to remove a tile to fit the brackets for the panels, it would crack all the tiles around it. And when they tried to removed the cracked tiles to replace them with good tiles, they would crack all the tiles around it.

Anyway, after a discussion with the company, they said the best thing to do was to remove all the old tiles (and insulation foam underneath) and re-tile the south face of the roof prior to installing the panels, which I agreed to since they gave me a very competitive price to do it.

The electrics are all in. You need space for an inverter (the heffing big box) which converts the DC energy from the panels into AC energy that it compatible to be fed into the national grid. You also get a little digital meter to show how much energy you've generated, and the whole thing is topped off with two isolator switches to shut it off.  You also need a spare slot on your main electricity consumer unit which is how the power gets fed back into the grid.

These are the 8 panels themselves. They're Panasonic HIT-N240SE10 and represent the cutting edge in solar power generation.  They're going up later this week (all being well) after which I'll update the blog.