Grid-connected solar - FAQs

How does a grid-connected solar PV system work?

A grid connected solar system is really very simple. An array of solar panels is fixed somewhere where it receives good sunlight - usually on your roof, although ground-mounted panels in the garden may also be worth considering where you do not have a suitable roof. Solar panels produce DC (direct current) electricity, which is ideal for charging batteries but will not power your household appliances. So a device called an inverter is then used to convert the DC electricity into 240 volts AC (alternating current). The inverter connects to the mains supply via a meter which monitors the total energy produced by the array. Grid-connect inverters are quite sophisticated (and hence expensive) because they have a number of safety features, and have to ensure that the waveform generated matches precisely the waveform of the electricity of the national grid to which it is being connected. Various solar panels can be used in grid-connected applications. The amorphous, flexible adhesive backed panels are great for metal 'standing seam' roofs, though most installations use conventional framed panels, such as the Moser Baer panels. Solar tiles, glass laminates and large panels designed for building integration are also available.

What will it cost?

This will depend on the size of the installation. The smallest installation that is likely to be financially viable would be around Ł10-12,000, for a 4kW system, which would usually be the maximum you could fit on the average house. But please give us a call to organise a quote and we can provide a range of price options for you to choose from.

How do Feed-in-tariff payments work?

To encourage the use of solar panels for generating domestic electricity, the UK government have brought in a Feed-in tariff subsidy scheme, (they call it the 'Clean Energy Cash Back scheme'), that pays you for each kWh of electricity you generate (whether or not you use it in your own property, or feed it back into the national grid). You also get paid a smaller amount for the proportion that you do feed into the national grid. This scheme makes domestic solar installations a genuinely attractive financial investment. However, to qualify for the scheme, your solar PV system has to meet strict standards and be installed by a certified installer such as ourselves. We offer installations both locally in Cambridge (where we are based) and the surrounding area. Ultimately what matters to most homeowners is the payback time - how long they will have to wait until the system recoups its own cost. Under the new UK solar feed in tariffs, a payback time of 10-15 years may well be realistic. The calculation is a complicated one and is dependent on the outcome of the ruling passed on recent changes to the feed-in-tariff

Will I need planning permission?

In most cases, no. As long as the solar panels are within 20cm of the plane of the roof, and do not protrude above the ridge line, then the installation counts as 'permitted development', and no planning permission is needed. This is true (since an amendment to the Town and Country Planning Act was passed in October 2008 - http://www.opsi.gov.uk/si/si2008/uksi_20082362_en_1) even for most installations in conservation areas, and even when the installation is on the principal elevation of the building and is visible from the highway. Council planning officers have been known to be unaware of the correct legislation - so if you get a difficult one, point them to the link above!

There are still a few cases where permission may be necessary, particularly on listed buildings.

Is My House Suitable for Solar Panels?

Find out more here

Can I do it myself?

Not if you want to claim feed-in tariff payments. It has to be done by an MCS-accredited installer. Sorry!

I'm not connected to the national grid - can I claim FITs?

Yes! Bizarre but true - you get the payments even if you are not feeding any electricity into the national grid.

For an off-grid system, you would need a battery bank and an inverter to generate 240V power, and you would get paid for all the electricity that you use from the battery bank. Perversely, this gives an incentive to use as much power as possible - so you can get paid up to 41.3p per kWh simply to generate electricity and waste it. The government were a bit daft thinking that one up.

We're very experienced in designing off-grid systems, so if you'd like us to help do get in touch.

You can read more on off grid systems.