• Can I install solar PV myself?

    To be eligible for the feed in tariff the photovoltaic system must be installed by a Micro-generation Certification Scheme (MCS) certified installer. It also needs to be signed off by an electrician, and by a registered “competent person” for building regulations. Hence this is not something that can be done DIY.

  • How can I get the most value from my solar PV panels?

    During the day you will now effectively have free electricity (up to a point). Hence you should run appliances such as washing machine, dishwasher, vacuum cleaner, electric lawn mower, electric oven during the day when the panels are producing the most electricity. If you have a large system you can use an immersion heater to heat your hot water using the free electricity being generated.

  • How do I know the solar PV system is working properly?

    The inverter displays figures of daily power consumption and electronic control unit provides information on the performance of the system via its LCD display. Your generation meter also keeps a running total of how much electricity your panels have generated. You send a meter reading off to your power company every quarter, and based on this they send you a cheque.

  • How long will the system last?

    System life is approximately 25-30 years. The are no moving parts. The panels are tested to withstand hail up to 25 mm in diameter. The panels power output is guaranteed to remain greater than 80% of the original output up until 25 years.

  • Is there enough sunshine for solar PV to work?

    Good quality, high efficiency photovoltaic panels work brilliantly in the UK climate. They work best in direct sunlight, but still work effectively on diffused solar radiation, and hence will provide electricity even on cloudy days. For the level of insolation in your locality check our solar map.

  • My panels appear not to be performing as I would expect. At the end of June on a sunny day at midday the panel output was 2 kWp. In the last three very hot and sunny days (July) the best output was 1.5 kWp.

    The panels’ output can be adversely affected by hot temperatures which is quite normal. When it is really hot and there is very strong sun, often the performance will not be as good as during cooler conditions. This seems counter-intuitive but is normal operation for all PV cells. (In very hot countries they use water to cool the panels) If you look at the technical specifications of your panels the nominal power (Pnom) drops by ~0.46% per degree that the panels are above 25°C. In very hot and sunny conditions the panel temps can get up to 80°C, which would give a 25% power reduction. This is in line with your observations. You will find that the peak output will usually be achieved on a day with scattered cloud when the sun comes out from behind a cloud and the panels are cool, the output peaks then starts to reduce as the panels heat up.

  • So how does solar PV work?

    Photovoltaic panels generate electricity whenever there is daylight. Any daylight will produce power, but the most power (the system’s rated peak power) will be produced with direct sunlight. They work summer and winter, 365 days per year. A typical household has a background electricity consumption between 500 watts and 1kW. The photovoltaic panels will exceed this amount for much of the day, hence your panels could be powering your house 100% for much of the time. Any excess power produced by the panels is fed back into the grid (where it will be used by your next-door-neighbours), and the power company pays you for this. Once installed the system is fully automatic and its performance can be monitored with the inverter’s display.

  • What are the benefits of solar energy?

    When you install photovoltaic solar panels in your home, you will reduce your impact on the environment. The system will pay for itself (typically in about 9-10 years). You will earn a significant annual income, whilst also reducing your electricity bills.

  • What does the inverter do?

    Photovoltaic solar panels produce high voltage (more than 400v) direct current (DC) electricity. It is the job of the inverter to convert this DC current to 240V 50Hz alternating current (AC), which is the standard voltage used by the appliances in your home. The inverter also has to match the voltage and phase of the alternating current that it produces exactly to the same phase and voltage as the grid. This enables the excess power produced by the solar panels to be directly fed back into the national grid for the benefit of everyone.

  • What is a kilowatt-hour? How is electrical power measured?

    Electrical energy is measured in kilowatt hours (kWh) also known as a “unit” on your electricity bill. A 1 bar electric fire consumes 1 kilowatt (1kW) of electricity, and if you leave it on for 1 hour it consumes a total of 1kWh. A 100W light bulb would have to be left on for 10 hours to use 1kWh of energy. But better to use an energy saving bulb that uses 10W, which would run for 100 hours before using 1kWh. If you think of the electricity like water, the power (measured in watts & kilowatts) is how fast the tap is running, and the meter measures how much you use over time (measured in kilowatt hours kWh).

  • What is the feed-in tariff (FiT)?

    The feed-in tariff is a system of government grants that pay people to generate energy from renewable sources. Once registered on the scheme the payments are tax free, index linked and guaranteed for 20 years. The payments are independently funded and administered by Ofgem. Once you are registered at a specific FIT rate that rate is guaranteed and not at risk of any government interference. (They are only able to change the rules for new entrants.)

    From 1 April 2012, in order to qualify for FIT payments properties will have to have an Energy Performance Certificate rating of ‘D’ or above. Details can be found here

    Details of the current rates can be found here.

  • What is the ideal angle to mount a solar PV panel?

    Usually when mounting on a roof just use the roof angle (they must be within 200 mm of the roofline to be permitted development and not require planning permission). For a flat-roof installation the latitude, wind loading, and shading of adjacent panels must be considered. Using a south facing panel in Southern England as the example (latitude 51° North). At the spring/autumn equinox the ideal angle for the panel is 51° to the horizontal. The earth’s axis is tilted 23°, so at the height of summer the ideal angle would be (51-23)=28°, and in mid winter (51+23)=74°. For maximum power generation the panels should be closer to the summer optimum, hence 30° is ideal. Using a shallower angle reduces wind loads and also reduces shading, so adjacent rows of panels can be mounted closer together. Hence 20° is also commonly used for flat roof and ground mounted installations.

  • What is the largest system I can have?

    There is no limit, but the highest rate paid per kWh for the feed in tariff is given for systems which are up to 4kW (peak power). This is measured by the inverter AC output, not the panel generation capacity.

    The latest feed in tariff rates are reproduced here. 

  • Where can the solar collectors be placed?

    On a roof or on the ground, ideally facings south, or anywhere between south-east and south-west for best performance. If your roof ridge is oriented north-south, you can install panels on each side of the roof (a dual-aspect installation). This works well since the east facing panel will take advantage of the morning sun and the west facing panel the afternoon/evening sun. This spreads the power generation curve so that there is less of a peak mid-day and gives more power in the morning and evening. In this configuration more panels can be attached to given size inverter. In terms of getting the most power out of a single panel it should be facing south.

  • Will I need planning permission?

    From April 6 2008, homeowners have been able to install solar panels, without needing to obtain planning permission. Size limitations have been set to reduce any impact on neighbours. Solar panels attached to the building must not protrude more than 200 mm from the roof slope. The only exception is if your property is a listed building or is in a conservation area, in which case you will need to consult with your local council planning department.

 

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