Fitting solar panels to your roof

Last updated Thursday 30 April 2009

A shining example... or an expensive shot in the dark?

Solar panels could slash your electricity bill and even see you selling energy back to the power companies. Brace yourself though - savings like that don't come cheap.

Even the pessimists don't expect the sun to pack up for another five billion years, so it's a fair bet that we'll run out of gas and coal before solar power. And getting your electricity this way means zero CO2emissions (excluding the ones that go into making the panels), so they're a big hit with the carbon conscious crowd.

So what's the catch? The price tag is one: upfront costs of 10,000-18,000 may cool your enthusiasm. And then there's the British climate, not famed for its long months of steady sunshine. On the bright side, you could still generate half the electricity you need every year.

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Photo: Fitting solar panels to your roof

Saves up to 1,100kg of CO2 a year

166 Bloomers are doing this

CO2 reduction 3 out of 5

Cheapness 4 out of 5

Popularity 3 out of 5

Cost 10,000 - 18,000

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It's Not Easy Being Green: Solar panels

Dick and James Strawbridge discuss the pros and cons of solar panels, and how to install them

In this article:

How does it work?

Regardless of whether you choose clunky roof panels or integrated tiles, the basic principle is the same. Solar panels are made up of a series of photovoltaic cells, consisting of layers of a semi-conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers causing electricity to flow. The more intense the light, the more electricity you generate - but remember, it's light and not heat that matters, so you're not totally at the mercy of the weather.

A two-way meter clocks up how much power you import from the national grid, but literally runs backwards (making you a profit) when your home is doing the generating. Or you can store the electricity you generate during the day in batteries for use during the night.

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How will it make a difference?

Pub Fact

  • The average UK house uses 4,150 kWh of electricity per year
  • Putting solar panels on just 4% of our deserts would keep the world's electricity-using population more than happy (IEA)
  • Domestic electricity consumption accounts for a substantial 30% of the national electricity used every year
  • The efficiency of sunlight-to-electricity conversion is only 15% less than the efficiency of fossil fuel-driven power plants but with zero CO2
  • Britain gets 1436 hours of sunshine per year on average compared to almost 3000 hours on the Mediterranean coast

A typical domestic system could save:

  • Over a tonne of CO2 every year - that's more CO2 saved than swapping your petrol car for an electric model
  • About 50% of a typical household's electrical demand, averaged over a whole year. (During the summer months, that figure rises to about 75% although normally around half of the electricity generated is used on site while the remainder is sold back to the grid.)
  • Something like 170 off your annual electricity bill - including the prospect of profit to be made from selling excess electricity back to the grid on sunny days. And bear in mind that the more electricity prices go up, the more money you're saving
  • Almost 60 from selling excess electricity back to the grid on sunny days

It's also worth noting that a report in the Guardian newspaper claims fitting solar panels will add 9% to the value of your property

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What's the debate?

  • "Where'd you think we are, mate? The Costa del Sol?" Even when the sun's on full beam over the UK, we get just 60% of the solar energy soaked up by the equator. Despite our fabled lousy summers, solar power looks a surer bet than wind power for the DIY approach
  • Detractors point out that Britain's energy demand peaks in the winter - just when solar generated supply will be lowest. This is true, and in addition to the lack of supply at night, means we're unlikely to rely solely on solar in the UK. However it remains a viable option to supplement other sources of electricity
  • There is certainly a debate about the energy that goes into making the generators in the first place (their 'embodied energy'). Enthusiasts, however, note that solar panels tend to generate five times as much energy as they consume during manufacture
  • Until the computer and solar industries stop fighting over silicon, critics complain that the price of solar panels will remain prohibitively high. But silicon shortages show signs of easing, thanks to growth in silicon recycling, thinner wafers, a growing market share for silicon-free thin-film technologies, and the increasing efficiency of solar panels

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What's stopping me?

"The start-up cost"

The start-up cost might dull the appeal. An average system costs 10k-18k and there are fewer and smaller grants available - the current grant is 2,500.

Payback periods (the time it takes you to make back your investment) have risen to over a century. But at least there is a payback period. No matter how much gas, oil or coal you buy, you never ever get your money back. Part of the payback comes from selling renewable electricity back to your energy company.

And the price of panels may come down. Global shortages of the high-quality silicon required to manufacture them are predicted to ease eventually.

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How do I do it?

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Comments

Richard Darlington, Oldham. 2009-02-04

In the programme you ask for comments on fitting solar and pv panels on listed buildings and in Conservation Areas. I sit on a Conservation Panel at our local Parish Council where I find my fellow members to be inflexible regarding alterations to historic buildings. In previous centuries buildings grew organically but now it seems we have to fix them like historic relics. One does not want buildings ruined but I would argue for them to continue to be living reflections of our age and that includes allowing solar and pv panels on roofs. I didn't like the panel covering a window in your programme but on roofs is fine.
We ourselves have had hot water solar panels for nearly 14 years and pv panels for five. We regard the pay back period as immediate. They cost no more than a kitchen or bathroom refit or new car and reduced our energy bills and carbon footprint from day 1. The pv panels have earned us 760 compared with 1,150 spent on electicity in five and half years. They have also helped reduce the country's dependence on imported energy. If everyone with a south facing roof installed solar panels we would make a real difference. So I hope your programme can encourage others to follow suit.

Baz, Shropshire 2009-01-29

The regulations involved for PV installations with a grid tie are very restrictive requiring authorised installers. This in addition to the high cost of the panels makes the pay back period very long. It is not a technology I would currently embrace. However, do not dismiss it, PV for isolated small scale users is economical, you can install these yourselves and do not have the cost of labour to add. Also consider solar panels for hot water or heating water to store to be later circulated through the central heating system. You won't get much heat in the winter, but in spring and autumn the heat will be there for those cooler evenings. This type of solar is much cheaper and is within the capacity of a competent DIY enthusiast.

Anonymous 2008-12-07

The claim that domestic PV systems can save "up to" 1.1 tonnes of CO2 is an underestimate. the average sized 2.5 kWp system will save 1.2 tonnes per annum, larger systems saving considerably more.

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Nitrogen oxides
Nitrogen oxides are compounds of nitrogen and oxygen, two elements that do not normally react with each other but will do so during high temperature combustion – such as in a car engine. Examples include nitric oxide (NO) and nitrogen dioxide (NO2), which contribute to air pollution, and nitrous oxide (N2O), which is a major greenhouse gas. Although its warming effect is far less than CO2, it persists in the atmosphere for far longer, so measured over 100 years its impact is 298 times greater.

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