PV Solar Panels

Greenenergy1

Hi all,

I'm looking to get PV (polyvoltaic) Solar panels installed on my house in Dublin City (south facing). I was hoping someone could help me with the following :

1)Do I need planning permission for panels
2)Optimum number of panels
3)Costs of installation
4)Savings on electric bills
5)Recommended installer

Any other advice would be gratefully appreciated

Thank you
Greenenergy1

mr chips

I live in NI, so I can't help you with 1 or 5 I'm afraid, but we got a solar array installed last year and I'm really pleased with it.  Ours is a 14 panel, 3.92 kWp array with an estimated annual energy yield of 3,276 kWh.  At the time of installation, we still got the benefit of a feed-in tariff and ROCs payments, both tied in for 20 years, and on that basis our return-on-investment period was estimated at between 7-8 years.  However, we've been able to heat our water effectively free of charge using the immersion instead of the oil-fired boiler for all but the three darkest months of winter, so that will cut the ROI period fairly significantly in terms of the reduced oil consumption (yet to be measured).
Our average daily usage before they were installed would have varied from maybe 9.5-11 kWh, depending on the time of year.  The array was installed at the end of August last year, and to date has produced about 2040 kWh in 258 days or 8 kWH per day.  However, the brightest/longest days of the year are still to come and the average to date includes the winter when some overcast/miserable days would have seen as little as 1.5 kWh - by contrast, the average over the past few weeks has been about 25 kWh per day.  Net cost of installation was a shade over £5900 sterling, for a ground-mounted array including about 50m of underground armoured cable, construction of the mounting frame, inverter, panels, all installation costs etc.
So far so good.  We have been producing a surplus for about six weeks now - however the fact that we get a feed-in tariff that in total nearly matches what we pay to import power from the grid makes a real difference, and unfortunately I don't think this will be available to you.  So you *might* benefit from a smaller installation that will meet your daytime needs during the brighter part of the year, and forget about any significant generation for the darkest 3-4 months of the year - others may have better advice for you there.  Despite the FIT, I'd still rather be able to either store our surplus or use it to generate more power for use at night, rather than exporting during the day and importing at night.  But the likes of the Tesla Powerwall etc are still way too expensive for us to consider at the moment.

quentingargan

1)Do I need planning permission for panels
There is an exemption for up to 12 sq metres which is equivalent to 7 panels or about 2kw

2)Optimum number of panels
As outlined, depends on your consumption. Most people in the south use a diversion device to get hot water from their surplus power, which would otherwise be exported. If you have a 200L cylinder, then a 25kw to 3kw system would give you most of your hot water in the summer months, assuming you use about 1/3rd of the power yourself.

3)Costs of installation
Depends on the roof height, access and roof covering.

4)Savings on electric bills
Depends on whether there is someone at home during the day to use the electricity produced.

5)Recommended installer
Can't do that here on Boards. You need to ask to be contacted by private message.

Greenenergy1

Thanks for the replies quentingargan and mr chips

I'm assuming that I will get roughly half the energy that Mr Chips system is producing if I go for 7 panels? Also, would I be correct in saying the payback on the install would also be half the time because I will be getting less panels?

Is there any way to use excess power for appliances during the day without using battery storage? Old fashioned electric timers?

Thank you

quentingargan

Greenenergy1 wrote: »

Thanks for the replies quentingargan and mr chips

I'm assuming that I will get roughly half the energy that Mr Chips system is producing if I go for 7 panels? Also, would I be correct in saying the payback on the install would also be half the time because I will be getting less panels?

Is there any way to use excess power for appliances during the day without using battery storage? Old fashioned electric timers?

Thank you

You won't get half the payback. The larger system is producing more power, so it will run some of your loads.

The most popular way of using your own electricity is a device that monitors your grid import/export and effectively runs your immersion on a dimmer switch to use all the surplus power. But be careful. There are cheap devices out there that use phase-angle switching. You need one that uses high frequency switching - they are more expensive, but the cheaper units may cause interference to your neighbours' devices.

Most washing machines and dishwashers come with a delay option so they can come on after 3 or 6 hours. You can use that to run loads during the day while you are out, but bear in mind if you have a 2kw system producing, say, 1kw of power, then a 2kw washing machine will run importing half the power from the grid. You would have been able to buy the whole 2kw at half price during the night rate if you have one.

mr chips

Plus the installation costs for a smaller system, e.g. 2 kWp instead of 4 kWp, won't simply be half those of a larger system - things like the inverter, cabling etc will still cost the same regardless of how many panels you install in a typical domestic setting. If you do go for it, to make the best use of the power your system produces you'll probably end up heating water, running dish/clothes washing appliances etc during the day when your panels are providing free power. You could even end up using your oven more often, e.g. to slow-cook through the day instead of cooking over gas in the evening! The calculating really needs to be done before taking on the expense of installing panels, in order to work out how much power you currently use, and also how you could change your usage patterns in order to improve your efficiency - especially if, as quentingargan says, you have access to a cheap night rate (which I don't, here). So the sums still may not add up.
Sadly, it seems that the lack of FiT in the south really alters the cost/benefit from a purely financial point of view, at least for now. The good news is that the cost of panels is still falling, and while larger-scale batteries (of the sort you can use to run the house) are only now entering the market at a cost of £5-6k, that cost also looks likely to fall reasonably significantly after another say 3 to 5 years or so. By that stage, it could be worth installing a bigger solar array together with a battery system so that you can actually use nearly all the power you produce, thereby giving a much more favourable payback period.
That said, the financials aren't the only reason to go for a renewable energy source.  We'd always hoped to get panels and/or a domestic wind turbine once we could afford it. Sure, the fact that over the medium term, our system will leave us slightly better off financially is a bonus - but while it was helpful that the upfront cost of installation had dropped to the point where we could take it on, ultimately it's not the sort of thing we'll ever get rich from. Even if we'd ended up paying the same for power over the long term, we'd have gone for the panels anyway on the basis that a lot less coal/gas etc would be burned in order to power our house.

Greenenergy1

Thanks again for the replies quentingargan and mr chips, very informative.

One last question if I may, what method should I use to calculate my energy needs now? Look at old bills and take an average over 12 months?

Thanks

Greenenergy1

quentingargan

I would use an OWL monitor. This gives an accurate assessment of your use at each hour of the day.

mr chips

If you haven't already had the use of a device like that one, then yeah - look back at your old bills, not just to work out an annual average but especially so you can see what your monthly/quarterly consumption is. You should see that you use less in winter than in summer, which of course is also when a solar array will provide the least. For example, our average consumption in summertime would drop below 9 units per day when the panels are providing us with anywhere from 15-27. But during the darkest winter months we would use around 11.5 units per day, yet the average supplied by the panels was probably only 4 or 5 - could be as much as 6 or 7 on those bright, cold days we sometimes get, but much less when it was dull and miserable, as little as 2 or even 1.

This is why getting them installed in time to get access to the feed-in tariff was so helpful for us, as it meant we could offset the cost of the panels with the extra annual payment. It's also why you should try and see whether the output from the panels can be used for pre-heating your hot water in winter, so that you use less oil/gas/electricity from the grid or whatever to get it to the temperature you need.

rolion

quentingargan wrote: »

I would use an OWL monitor. This gives an accurate assessment of your use at each hour of the day.

From personal experience,not the best indicator in combination with PVs.