£700 from photovoltaic panels
The roof on average size house will probably limit you to a 3KW photovoltaic installation. The full installation will cost about £5,500 and generate an income of around £700 a year, giving a payback of around 8 years.
The £700 income is guaranteed for 20 years giving you a simple profit of around £8,000 after maintenance costs.
The PV panels are guaranteed to be more than 80% efficient after 25 years and will therefore reduce your electricity bill by around £450 in 2040.
some photovoltaic facts
The average installation in the UK is a 3.5KW system.
IKEA will install a 3.36KW system for £5,700 including VAT.
a south facing roof is 98% efficient
a south-east or south-west facing roof is 95% efficient
an east or west facing roof is 85% efficient
Therefore returns of £675 on south facing roof become £650 for a SE/SW roof and £580 for an east/ west roof.
system cost & paybacks
a 2KW system will cost around £4,300, has a payback of around 10 years and yields a £5,000 profit over 20 years
a 3KW system will cost around £5,500, has a payback of around 8 years and yields a £9,000 profit over 20 years
a 4KW system will cost around £6,100, has a payback of around 7 years and yields a £13,000 profit over 20 years
a 2KW system will cover 14m² of your roof
a 3KW system will cover 21m² of your roof
a 4KW system will cover 28m² of your roof
There are around 20% system losses (inverter, wiring..) so
a 2KW system will generate around 1,600 units (KWH)
a 3KW system will generate around 2,400 units (KWH)
a 4KW system will generate around 3,200 units (KWH)
The average electricity bill in Northern Ireland is 3,600 units or £610 a year. Generally half the electricity produced will be used by the dwelling and the other half will be exported to the grid.
the future of photovoltaic panels
Prices of PV panels have dropped 80% since 2010,making installation of a PV system a reasonable investment when you factor in the NIROC subsidy.
PV panels will continue to get incrementally cheaper through economy of scales, omprovements in panel quality and efficiencies. Standard panel efficiency is expected to grow from around 15% to 20% in the next few years. Some manufacturers have just announced panel efficiencies of 25%.
As PV costs fall, the NIROC subsidy will fall to ensure PV panels remain a reasonable investment. Power generated from PV panels in the UK have grown from 17 to 2,015 gigawatt hours between 2008 and 2013. A gigawatt hour is 1,000,000 units of electricity.
overview of 3KW photovoltaic system
Electricity generated by the photovoltaics are measured in the same units that your electricity bill is calculated (1 unit = 1 kilowatt hour).
The Northern Ireland Government's NIROC scheme guarantees payments of 16.96p for each unit generated for 20 years to allow you a safe return on your investment.
So electricity generated and used by you, you will save around 17p and earn you around 17p (NIROC), making you 34p a unit better off.
Electricity generated and not used by you will be exported back to the grid and you will be paid 5.59p per unit. You will earn around 22.5p for exporting units (16.96p (NIROC + 5.59p).
An average 3KW system will generate around 2,400 units of electricity a year. Most of the electricity will be generated between 10am and 5pm so generally 50% of the electricity gets exported back to the grid.
If your roof is more or less facing south and there is no overshading, then you will earn around £425 from the NIROC payments, earn £70 from exporting electricity and save £210 of your electricity bill, making you around £700 a year better off.
The system will cost you around £5,500 giving a simple payback of around 8 years.
However you should factor in cleaning the panels twice a year which may cost around £50. Additionally the invertor on the system generally lasts around 20 years and will cost £1,000 to replace.
Therefore after 20 years your returns will be around £14,200.
So your £5,500 investment should earn you around 8% interest a year for 20 years.