Free home energy is now cheaper to make

New grants for photovoltaic panels announced this week will finally encourage real micro-generation in the home, writes Kya deLongchamps.

Creating clean, free electricity from your own roof? Minister Naughton’s announcement of grants towards PV panels and storage batteries this week means the householder will now get €700 per 1kWp panel, (up to a total of €3,800), to help reduce our national load of greenhouse gas emissions, while at the same time, decarbonising our electricity supply. Batteries will be subvented to the tune of €1,000 per unit.

How does domestic photo-voltaic work?

Not to be confused with solar thermal panels which help to heat your hot water, photovoltaic panels (PV) uses semiconductor materials that react to solar radiation to create electricity— or put simply — they run on light, not heat.

The reaction is used to generate (DC) electricity — clean, independent energy. Using what is termed an inverter (this unit sits on an inside wall and is sized to handle the watts generated from your array of panels) — the DC current is changed to the AC current we use in the home.

With heat pumps leading the way to the all-electric home, power bills will inevitably spiral — so the argument for domestic micro-generation is obvious.

The amount of power you can generate from PV during daylight hours depends on the number of panels making up your roof-mounted system. There are anywhere between 60-144 solar ‘cells’ in a domestic PV panel, and householders can choose from 1kW – 4kW systems delivered in multiple panels.

Without a battery to store the surplus energy created by day, a ‘diverter’ can send energy to heat your hot water cylinder Any unstored surplus energy not sent to a battery or diverter, is sent back as a credit to the national grid. This is a real time system — use the power or lose it — unless you invest in large capacity batteries, (off-gridders have used old submarine batteries in the past).

How much can I expect to save on my electricity bill with a PV installed?

The average household draw of electricity in Ireland according to the Commission for Energy Regulation is around 4200kWh pa (check your own bill to work out your household usage). A low energy (passive/nZEB) house should draw down a lot less power.

The size of your panel, the inclusion of a battery and/or diverter system, usage discipline and the vagaries of the weather will all have a part to play here, but savings of up to 75% are suggested for a significant spend that includes a whole-house retrofit.

If Electric Ireland are to be believed, and to be fair they put some figures up for review with their product information, a house in Cork carrying one of their standard 10.2sqm panel systems on a south facing roof would expect to save around €253 per year (based on 18.5c per kWh on 1610kWh and 85% of consumption of energy generated by the PV system). That’s a click under 40% of the average household kWh use.

It all comes down to system size and the best use made of that power. Berth Sheehy of Energywise Ireland (Cork), offers sunny figures for best practice and a larger array. ‘A south facing three kilowatt system in the south of Ireland can generate 2900 kwh of electricity.

“Assuming we use 80% of the electricity generated in the home we can save approx €400 per year and additional savings can be made by fitting a solar switch to divert surplus electricity to heat water.”

There’s no escape from standing charges and the PSO Levy (plus VAT), on the remaining draw from the grid. Software supplied with your system can help you to monitor your savings using your tablet, PC or mobile.

What does it cost to buy and install a PV system?

Prices for PV systems have fallen significantly in the last 10-15 years and to achieve the grant, all installation should only be done by a dedicated SEAI registered PV engineer, and your supplier will in most instances, offer this service.

The cost for a 1.25kWp (Wp = peak wattage or max capacity) system generating around 800kWh (hours), of power per year from a south facing roof will start in the area of €3,500 and depends on brand and the number of PV panels installed.

Electric Ireland are offering systems that include a diverter (to help heat your domestic hot water) from €4,490 installed, interest free with a 20% deposit for qualifying customers (€99.78 monthly for 3 years). They include an energy app free for the first three months,

An average of €4,400 - €5,000 for a larger 2-3kWp/8-12 panel system installed and including an inverter and diverter (for hot water), was quoted among other suppliers questioned. Payback with grant aid can be as little as 10 years, keying in any ongoing rise in utility bills.

What about battery storage?

Rumours abound about US multinational, Tesla stepping in as supplier of integrated ‘tile’ panels and batteries to utilise out surplus energy, that otherwise ‘spills’ back to the grid. One PV supplier I spoke to told me they still regarded domestic battery storage as ‘evolving technology’.

Solar Electric in Enniscorthy, County Wexford, supply German-made Sonnen batteries measuring 60 x 80cm 20cm and wall mounted, which can be used singly or banked to store and draw surplus energy produced in daylight hours.

Solar Electric’s, Robert Goss, suggests an improvement of 50% in self-produced energy with PV alone, to as much as 80% with a battery. In terms of PV panel system size, he suggests a 3 kWp PV matched to a 7.5 kWh battery. Cost for adding a battery? Double your PV price —that’s €5,000 for a battery onto a €5,000 spend on the standard PV system and installation.The SEAI grant towards a battery is now €1,000.

Brian Denvir, Solar PV Coordinator for the SEAI explains: “This example would be for a home with below average electricity consumption. A 3kWp system will generate around 2,600kWh of electricity per annum. Therefore, if the home’s average annual electricity demand is only 3,250kWh, then yes, this could reduce their grid electricity consumption by up to 80% assuming that the battery allows them to use 100% of the electricity they generate.

“Note that an 80% reduction in grid electricity consumption does not mean that the homeowner’s electricity bill will reduce by 80% —there are fixed charges on a homeowner’s bill which cannot be avoided.”

Under the SEAI grant scheme, any installation over 2kWp must install a battery. with €1,000 offered towards battery storage. There are criteria including the construction age of the house, which must be built before 2011 and the grant is paid after installation, and only following work by an approved installer.

Others savings you can follow up, apart from taking interest-free offers from reputable suppliers, is to offset some of the 23% VAT you spend, in a two year tax claw-back through the Home Renovation Incentive Scheme worked together with the SEAI grant aid. Solar PV qualifies. “SEAI will be creating a solar PV calculator so that homeowners can estimate how much money they could save and what kind of payback period they can expect,” says Brain Denvir.

Is PV for me?

Solar-thermal or PV, where should people direct that retrofit budget first?

“If consumers are looking to lower their energy bills the first thing to deal with is energy efficiency measures such as loft and wall insulation, upgrade of heating systems and heating controls — most homeowners are entitled to grant support from SEAI for these measures.

“After that it really depends on the home and the energy consumption of the occupants as to whether solar thermal or solar PV is preferable,” says Brian Denvir.


- See

- (Sonnen)

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