Frequently asked questions

Questions & answers

How much space on my roof do I need for a solar PV installation?

Our grid connected systems start from around 1kW peak power, this occupies between 5 to 6.6 square metres on your roof.

How much electricity does a PV system output?

For every kW of peak power installed on a South facing roof the system will generate around 800 kWh. This reduces by around 15% for an East or West facing roof.

How much does a Solar PV system cost?

Installed prices (including VAT) start from around £1000 to £1500 (inc VAT) per kW peak power depending on the type of panels and inverter and the complexity of the installation. The Feed In Tariff (FIT) has now come to an end but there are ways to export the excess electricity and get paid for it.

Do I need planning permission?

Within certain criteria our roof mounted systems do not need planning permission unless the property is listed or in a conservation area. Some flat roof installations may need planning but the planners generally look favourably on Solar PV. If the system is to be ground mounted then permission will be needed if the system is over 9m sq. That's about 5 panels.

Do I need to inform building control that I intend to install a solar system?

Greencap Energy Ltd is certified to self-certify the electrical and structural elements of a domestic PV installation, and will notify building control once the system is installed through our certification bodies.

Will my roof be strong enough?

Most roofs are strong enough to take a solar installation without any reinforcement, however we will carry out a full survey of your property and consult our structural engineers if required.

Do I need to inform my electricity supplier?

For systems below 16 Amps output (3.68kw peak power) we will inform them once the installation is complete. For systems larger than 16 Amps we will require permission in advance from the network operator - we will arrange this permission. Larger property's may have 3 phase supply's from the grid and in these cases we can install up to 11.04 kw without permission.

What is the payback for a solar PV installation?

We would expect a system to pay for itself in approximately 8 to12 years.

Can I export any of the electricity I generate?

Yes, all unused electricity will automatically be exported. Your electricity company can fit an export meter. Please do not confuse the export meter with the generation meter which we fit as standard on all our installations. Another way is to fit a diverter which will send all your excess electricity to your hot water tank.

What is a kWh?

A kWh (pronounced ‘kilo watt hour’) is a specific amount of electricity. 1 Kwh is identical to 1 unit of electricity that is shown on your electricity bill. An electrical item having a rating of 1kW will consume 1kWh for every hour it is on at full power.

What does the inverter do?

The solar photovoltaic panels generate direct current (DC), this is not directly compatible with the 240V alternating current (AC) that is used in your property. The inverter converts the DC power to AC power that can be used in your property.

How does the electricity I generate get in to my wall sockets?

We connect the system to your fuse board (consumer unit). The electricity will automatically flow from there to wherever it is needed. If you think of two hoses, one being high pressure and the other low pressure. The electricity you generate is like the high pressure hose. It surpresses the low pressure from the grid. Therefor it will only let the grid (low pressure) onto the fuse board if you are useing more that you are generating.

Are solar PV tiles available?

Yes, PV tiles are aesthetically very pleasing and are becoming more popular, the installation cost will be higher ( 4 times plus) than large ‘on-roof’ or in roof panels.

Will I have electricity during mains power cuts?

For the safety of the workmen working on the grid, Solar PV systems do not operate during power cuts.

Do I need a three phase electricity supply?

Systems up to about 7kw peak power can sometimes be accommodated on a single phase electricity supply, however we do need to seek permission from your Distribution Network Operator (National Grid). You can expect the DNO to require a 3ph for any systems over this.

Do your prices include for Scaffolding?

We do not include for scaffolding in our prices unless there are specific requirements for us to do so.

What is the difference between monocrystalline and polycrystalline PV panels?

Monocrystalline (Black Panels) solar electricity panels tend to be slightly more expensive than polycrystalline (Blue Panels)panels, however monocrystalline panels are regarded as having a higher output per kW peak power installed.

Will PV systems be dropping in price dramatically over the next few years?

Many developments are taking place in the PV industry and popularity is increasing. However, we would expect prices and performance to change gradually rather than dramatically.

Is efficiency important with solar panels?

Often not, the efficiency of a panel relates to how many watts a panel will produce. Only when suitable roof area is at a premium does it make sense to choose high efficiency panels, this will maximise the amount of power that can be generated from a roof. Greencap Energy can supply high and standard efficiency modules. Ultimately a 4Kw system is a 4 kw system. It can be made up of lower efficiency 250w panels of high efficiency 340w panels.

Whose panels do you use?

Typically we use high quality panels from JA Solar and Panasonic but we always try and supply a panel that suits our customers requirements in terms of price, guarantees, manufacturer and looks.

What guarantees will I receive?

Panels generally have an output guarantee of 25 years. Inverters normally have a guarantee of 5 to 10 years. Most other components and labour is usually guaranteed for 2 years and is covered by warranty insurance. Check your quotation for specific details.

Are your panels approved?

We only use the very highest quality of materials. The panels we use meet all the required standards including TUV and MCS approval.

Will an electrician fit the panels to the roof?

No, all roof work will be completed by our trained roofing specialists. We use our electrician for electrical work and our roofers for roofing work.

How are the panels fixed to the roof?

For standard roof we use rigid aluminium brackets that are fixed directly to your roof rafters. The brackets hook out from underneath your existing tiles. We do not drill tiles/slates or use mastic/silicone to weather proof your roof as these techniques do not have a long life span.

How long will the installation take?

On residential properties a system will normally take a day to fit the panels. After they have been fitted properly, a qualified electrician will visit you within a few days to connect the system.

How much do the solar PV panels weigh?

Normally about 13kg per m2.

Are the solar PV panels fragile?

Solar PV panels are very robust and can withstand the normal stresses subjected by nature.

Can I heat water with solar PV panels?

Once the panels have created electricity you could connect this to an immersion heater to heat water. Ask us for more information about controllers availlable for this.