On a bright day, an average of 1000 Watts (1kW) of solar energy hits every square metre of the earth. This is one hell of a lot of energy - if only we could capture it! Solar panels (made up of lots of solar cells) cleverly convert this solar energy into a handy form for us to use - electricity.

Solar photovolatic (PV) panels have been around for years on calculators and things like that. The technology has come a really long way since then, but they're still an expensive way of powering your home. They are great for remote power though, like sheds and outbuildings.

How much solar energy is really available where I live?

Well, you might not think that the UK is a great spot for solar panels. Certainly, compared to the Sahara desert, we're obviously not going to get as much sunshine. However, modern solar panels work pretty well even when its overcast.

Apart from the actual hours of sunshine, there are two important things that affect the solar energy you can pick up - the latitude of your house (more northernly locations are at a steeper angle to the sun so get less energy) and the UK is fairly northerly, we get less of this energy than we'd like.

Map showing the average solar radiation on a 30° incline facing due south (Source: The Solar Trade Association)

Installing solar panels on your roof - a case study

One of our website visitors, Matt, has recently had a 1.5kW solar pv array installed on the roof of his house by Dulas Ltd. He's very happy with it so far, but told us it was a bit of a struggle to make it happen - so here's his account of the highs and lows of getting solar power on your home.

The first step was to make sure the house was up to scratch in terms of energy efficiency, which is one of the criteria for getting the government grants (eg you must have energy saving light bulbs). I'd been disappointed a few years ago by some low quality bulbs from Ikea so I was pleased to find the ones available these days are much better and it was easy to convert the house to low-energy lighting. We also made sure the roof was well-insulated.

Having decided that the wind speeds were too low to consider a wind turbine, I settled on solar pv panels, and contacted various companies to get advice and quotations. My experience wasn't a good one and got very frustrated with certain outfits promising everything... and delivering literally nothing. But after a visit to the Centre for Alternative Technology (CAT) in Wales, I found Dulas Ltd.

Getting the grants

Dulas sent me a self survey form which I promptly filled in and returned to them. But then in January an email arrived from Dulas saying that because of the complete mess the DTI is making of the grants system they wouldn’t be able to complete domestic installations -the chances of getting a grant were too slim. Undeterred, I e-mailed them back and assured them that if anyone will doggedly sit up all night trying to secure a grant, it is me. After some persuasion they finally agreed to quote because of my insistence...they kind of believed I’d get a grant! 

On the 1st March the £500,000 allocated to the Low Carbon Buildings Program ran out in just 70 minutes. I logged onto the application website at 8.50am and just kept refreshing the page until it allowed me to make an application. I got the grant application approved at 9.12am. So my tip is, make sure you’ve got all the information you need prepared, and keep hitting that refresh button!

Getting the wiring sorted

With the grant in the bag, Mark from Dulas Ltd arrived on the 4th April in advance of the main kit to complete the internal wiring.

This was impressive - the invertor and requisite isolators went up in the loft, and he managed to seamlessly feed the cabling down through the house, and hook it up via another isolator and energy meter (see left) into my fuse board. This took about 6 hours in all. I can’t emphasise enough how valuable it was having a very experienced electrician to do the job. Walking around the inside of the house, you'd have no idea there was a renewable energy system installed at all!

The panels arrive

On the 16th April the Dulas team were back to install the roof system. I had a mad panic when my scaffolding didn’t turn up when expected but all was fine by the time the solar panels arrived. Then everything started to take shape very quickly - by lunchtime the Unirac roof system (which holds the panels was in place, see right) and the first two panels were fixed on.

By 4.30pm all twelve panels were on and connected up to the invertor. The following morning the system was tested and finally signed off. In all the install took about two days.

Performance output

Since the system started generating we've had an average of about 7kWh a day, with a maximum output of 1632W so far, not bad for a system rated at 1560w. I’m signing up to the Good Energy’s Home Generation scheme and so far I’ve generated £2.52 at 4.5p per kWh.

The components

The quality of kit installed is excellent - the wireless Fronius display gives a constant feed of data and displays everything produced now, that day, the year and since installation.

I’ve even taken the display unit down the road to see if it still picks up and it does...nearly 200 metres away! The invertor automatically starts up and shuts down when it can’t generate enough to keep itself going. When shut down it doesn't use any power, but still manages to know when the sun is up! We're very happy with the whole system and feel that the entire experience has been in no small part due to getting an experienced installer.  

The PV array and system that Matt bought consisted of:

• 12x Kyocera 130GHT-2 130w panels (£5405.40 inc VAT)
• Unirac mounting system (£519.75 inc VAT)
• Fronius IG15 inverter (£1080.45 inc VAT)
• Fronius wireless display (£220.50 inc VAT)
• Elster A100c energy meter
• Plus isolators and wiring and labour = total invoice of £10055.85 inc VAT.