Two years ago, we installed solar hot water and photovoltaic panels on the roof of our house in North Oxford. The panels have worked well - much better than was predicted - and the financial returns are acceptable. We have now managed to sign up to become a recognised supplier of renewable energy.

Vital Statistics

This property was built between 1700-1920. It is a semi-detached house with 3 bedrooms, located in an inner-city area in the South East. The household is parent(s) with children, with an average occupancy of 3 all year round. No planning restrictions are in effect.

Annual Energy Use

Electricity: 600.00 kWh (Renewable)

Power Generation

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Solar installations on new houses

Do they make sense?

Two years ago, we installed solar hot water and photovoltaic panels on the roof of our house in North Oxford. The panels have worked well - much better than was predicted - and the financial returns are acceptable.

Getting a quote

We had difficulties getting installers to come to quote. Then, as now, there are very few companies in the Oxford area that work with solar equipment.

The quotes we got varied considerably. We ended up using SolarSense UK in Bristol and would recommend them highly. Their quote for 2 kilowatt peak of photovoltaics and 40 vacuum tubes was about £8,300 after grants. The cost of solar electicity has now gone up because of the worldwide boom in demand for silicon for panels. On the other hand, the cost of solar hot water has gone down. We got a significant discount over the cost of single systems because the installer only had to put the scaffolding up once.

Very roughly, after grants the cost could be shared £3,900 for the solar hot water and £4,400 for the PV. If put up on its own, PV would be considerably more expensive.

Installation

This was quick and efficient. It took a team of electricians, roofers and plumbers about four days to do the work. Disruption was minimal. We needed a new hot water tank, and we had the sophisticated electronics for the PV installed in our garage.

Performance

Last year, we generated about 1,500 kilowatt hours of electricity. If our roof was south facing, this would have been perhaps 15% more. I can't be as precise with the solar hot water, but I suspect we used very little gas for water heating between April and September. The temperature got very hot (over 90 degrees) on some days and this is something one needs to be careful about.

Savings

In the last few weeks, we have signed up to become a recognised generator of renewable electricity. (In the past we had been part of an informal scheme with npower, but this was amateurish and badly run).

To become one of the thousand or so recognised generators (along with Sizewell B and Drax) we had to fill in an intimidating form from Ofgem. Though long and full of jargon, this was not very difficult.

We also signed up with Ebico, the ethical gas and electricity supplier. They actually get their electricity from Scottish and Southern, and so we are selling our exported electricity to this company. They will pay us £46 for every 1,000 kilowatt hours (Megawatt hour) that we generate. They do this because all generators (such as S+S) are obliged to have a portion of the electricity they sell from renewable sources. The price they pay is approximately the auction price of a megawatt hour of accredited electricity, so it is a fair return. They also pay us for all the kilowatt hours that we export on to the local grid. This is 4pence a kilowatt hour.

What does this all add up to? Let's assume we generate 1,500 kwh a year and export 600 of this total, using 900 kwh ourselves.

•  Electricity we generated ourselves that replaced kwh that we otherwise would have bought - 900 kwh * 9p = £81

•  Payments for all the kwh we generate (renewables payment) - 1,500 kwh* 4.6p = £69

• Payment for kwh exported to the grid - 600 kwh* 4p = £24

•  Total = £174

Put in carbon terms, our PV saves about two thirds of a tonne of carbon dioxide every year.

This a return of approximately 4% tax free and therefore compares well with a building society account. But if electricity prices stay the same, we will only see payback after 25 years. However, as I have written in my book 'How to Live a Low-carbon Life', people find that their behaviour changes when they install renewable technologies: they become much more 

energy aware. In our case, the reductions in electricity demand (which was previously unnecessarily high) have been much greater than the formal numbers would indicate. Our actual savings have been well over £300.

What about the economics of solar hot water? This is more difficult to calculate, but estimates I have done suggest a saving that is broadly comparable to the PV panels and therefore a slightly faster payback. Detailed numbers are in 'How to Live a Low-carbon Life'.

Overall

Nevertheless, we are very glad we installed the solar equipment. It has saved reasonable sums of money and carbon dioxide and it has made our household vastly more energy aware. It has also excited interest in friends and neighbours and several households have put up their own panels after visiting our house to see how the equipment worked.