Solar PV FAQ

Solar PV FAQ

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How many PV panels are required?

Domestic – 4kW (12-16 panels) require 20-30SQM of roof area depending on panel efficiency.

Commercial – The main limit is available roof area and size of existing grid connection. A 50kW (200 panel) system requires 300-330SQM.

How much do PV systems cost?

Costs have fallen considerably since the FIT scheme started in April 2010.

4kW mounted on a tiled roof costs £6500-7000 including VAT, installation and scaffolding. A BIPV roof integrated system will cost more and will need to be quoted on a case by case basis.

A 50kW commercial PV system for business will range from £50,000 to £60,000 (ex VAT) depending on type of roof, mounting system and grid connection.

Contact us for a free desktop survey and quote.

Can I get a grant?

The Government replaced capital grants with the Feed In Tariff Scheme (FITs). very attractive returns can be achieved with FITs so for more information on how much you can earn visit our FITs page.

How much energy does a solar pv system generate?

A South facing unshaded 4 kWp (12-16 panel) domestic PV system will generate approx. 3700 kWh (units) per year. This is based on the governments standard method to calculate performance (MCS Solar PV Calculation).

The electricity used by a typical UK household is 3300 kWh per year (source: Energy Saving Trust).

What happens to the electricity you do not use?

Surplus electricity is automatically ‘exported’ back to the grid. Currently if your PV system is less than 30kWp in size you will not require an import/export meter, with exported energy deemed at 50% of what you generate. Visit our FITs page for information on the latest export tariff rates.

To get the best savings we recommend that you aim to use as much energy on site as you can as the rate paid for imported energy exceeds the export tariff.

Timing appliances to be on by day, using load management systems or battery storage are all methods that can successfully maximise onsite solar energy consumption.

Do solar panels really work in the UK?

Yes. Solar energy is extensively installed across central and northern Europe, particularly in Germany which has a very similar climate to the UK.

The performance of any solar panel system depends on where you are in the UK and which way the panels face.

The amount of energy generated varies across the year, with up to 5 time more electricity produced in July than in December.


PV solar systems require minimal maintenance due to there being no moving parts.

The Solar PV Inverter, usually located inside the building, will likely require replacing after 10-15 years. Contact us for latest replacement costs.

Solar PV Panels generally self clean with wind and rain if installed at a minimum angle of 10 degrees.


Payback depends on various factors such as geographical location, orientation, angle and system size. Domestic systems payback in 7-8 years if installed on-roof.

Commercial PV systems can payback in as little as 5 years, or less when considering tax breaks which are currently available in the UK until the end of the 2014 financial year.

Contact us for a free consultation.

How long do solar panels last?

Solar PV panel performance is guaranteed for 20-25 years. Panels are usually protected against defects for 10 years and have an expected lifetime of 40+ years.

Solar PV Inverters should last 10+ years although typically come with a 5 year warranty. Extended warranties of up to 20 years are available, however, as these tend to cost the same as a replacement inverter at today’s rates we recommend against investing in extended warranties upfront as costs have been demonstrated to come down as the industry matures.

What happens at night?

When it goes dark your existing mains electric supply takes over, unless you invest in battery storage. The transition between grid and solar electricity is automatic, so you will never notice any change.

What happens if there is a power cut?

If you experience a power cut your photovoltaic system will go into standby mode until the grid connection is re-established. Some Solar PV Inverters can still produce energy even during a power cut but most do not.

Energy Performance Certificate (EPC)?

An EPC provides an energy efficiency rating of your property, with A being very efficient and G being least efficient.

Domestic and commercial properties must have achieved at least a ‘D’ rating with the solar pv system installed, unless the building is exempt (e.g. unheated farm buildings do not require an EPC).

We can arrange an EPC survey for you and will even cover the cost if you proceed with a solar pv installation with us. Arrange your EPC today.

Commercial PV Grid Requirements

The main limitations to the size of PV system on a commercial PV installation are the area where panels can be located, and the size of the existing grid supply. FITs tariff bands also have an effect as they affect the capital return i.e.

An 11.04kW 3-Phase system is the maximum size that can be connected under G83/2 which does not require Distribution Network Operator (DNO) notification prior to installation.

Anything greater than 20A per phase will require a G59/2 application before installation. We will complete this for you as will require technical details of the PV system design. Some DNO’s will charge to assess suitability of your existing connection, others will not.

For larger arrays the transformer and supply cable will require upgrading. DNO’s will quote for these works and advise which elements are non-contestable (i.e. elements only they can complete). Contestable works can be completed by suitably qualified contractors.

Import/Export Meters

Systems greater than 30kW will require an import export meter. Good Energy will pay Import and Export tariffs for larger systems and can also arrange for installation of the meter. In other cases you may need to appoint a Meter Operator (MOP) which will meter imports and exports however both your energy supplier and export tariff provider must both sanction this.

Genfit can handle this whole complex process for you.

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