Solar Panel installation basics

mcn99

Hi,

I'm in the very early stages of researching fitting solar panels, so really looking for some pointers. Apologies if wrong forum thread

I have a large south facing roof, situated in south of scotland, no trees obscuring roof.

As both myself and family are almost always in during day and also  work from home, is it really worth looking at storage ? as most power generated could be used.

Ideally i was looking at something bigger than the standard 4kw, but confused about rules that limit the output to connect to grid, is this a real problem.

Also looking at what is the realistic payback period, for say fitting a 6kw system,  15 years ? and what sort of installation cost should i be looking at.

Does anyone have anygood links to guides on Solar installation,

Thanks in advance

arty688

Hello,

Payback calculations are individual biased on how much of the generation you will use which is linked to how much electricity you use.

Bigger the better there is a DNO export limit of 3.68kw , over that there is more paperwork but worse case is that you will be limited to 3.68kw.

With storage payback is even harder to work out but its not all about payback remember.

for An idea of whats out there I would do a online quote and see what they come back with , from my experience they are not too pushy and don't bombard you with phone call for ever more. I think i got some quotes from first4solr and contact solar but I haven't commited yet so have no idea what they are like.

Martyn1981

Hiya. I did put together a PV basics in 2012 from the point of view of PV'ers. It's now quite a bit out of date, but you may find a quick read through worth it, just as a starting point. I'm sorry about all the broken links, and part two can be found on the 10/12/12.

Solar PV – Frequently Asked Questions and Answers

Laycity

I've had my solar 3 weeks. 4.74Kw array SSW facing in Lancashire. I've calculated approximately 12 years pay back for me but my primary aim is to be green, reduce expenses as I go into retirement and give me the options if I get an EV in the future. If your main concern is return on investment do something else, invest in a positive change fund or similar for 15/20 years.

We both work from home and i have really tried to use all the generated power (to an obsessive degree) but have only managed 35% usage. That's about the figure everyone on here and my installer quotes regularly, but I was quite confident we could better it. Wrong! I'll expect that percentage to be slightly higher in Winter and a bit lower in May/June. I'm exporting at 3p /kWh but it's really frustrating me having to buy that back a few hours later at 5/6 times the price.

Hence why I'm getting a Powerwall in October, excess solar will go straight here as well as the ability to charge at Octopus Go Faster rates. This won't decrease my pay back time but gives me maximum flexibility and options in the future. Plenty on here go the DIY battery option which is obviously more 'moneysaving'  

ABrass

I'm currently looking at solar panels.

I'm trying to find a quote that's likely to save me more money over 25 years than overpaying the same amount on my mortgage. Which for me is working out at around a 12 year repayment target. That's not easy.

So far I've had quotes ranging between £1.13 per kWh and £1.5 per kWh. But for quite different systems. And at £1.5 it isn't worth doing.

Reed_Richards

mcn99 said:

I have a large south facing roof, situated in south of scotland, no trees obscuring roof.

As both myself and family are almost always in during day and also  work from home, is it really worth looking at storage ? as most power generated could be used.

How much electricity do you actually consume per day?  How much of that is consumed between (say) 10:00 and 16:00 which are the peak hours for summer generation (south facing).  I would be surprised if you could use more than 9 kWh during those six hours unless you have electric cars to charge.  It might be different in winter if you use electricity for heating, but you will also generate a lot less power then.     

[Deleted User]

You can put as much PV solar on your roof as you want. Adding a Powerwall 2 adds an extra level of complexity as all batteries are treated by DNOs as potential generators. Your installer will submit the appropriate paperwork and you will pay c.£350 for the DNO to review your proposed installation. They will do this by looking at the local electricity infrastructure and its ability to accept exported energy. 

The application will either be approved without limitation or a total export limit will be imposed. Your installer will then have to ensure that the solar inverter and Powerwall 2 are set up not to exceed this limit. I have a 7kWP array and a Powerwall 2 and I have an export limit of 11kWs. Others are not so lucky.

Payback. I would be interested to know how you made this calculation? If you are using your supplier’s fixed rate then you are deceiving yourself. I am on Octopus Go: do I calculate my payback time on the 5p Offpeak cost or the peak rate of 14.63p/kWh. Solar alone will give you a shorter payback time than solar with a battery.

To get payments for any energy you export, you must have a smart meter and an export MPAN. Octopus also states that all installations require MCS installation.

Ectophile

Unless you have some appliance that uses a lot of power for hours on end, you aren't going to get anywhere near using all the electricity you generate.

Any appliance that plugs in will use less than 3kW, and most high-power ones only use the full power for a short time.

Exiled_Tyke

On the subject of storage, batteries are not yet cost effective. A view shared by those of who have them.  

However be aware that your comment 'most generation can be used' is probably not the case. In the height of production time (early summer) you'll be generating a lot more than you need. In December and January you may be averaging one or two kWh a day and have nowhere near what you need (nor enough to store).  

A few us with batteries are on Octopus Go (or Agile but that's not great value for money these days) and buy cheap electricity in the night. 

mcn99

Thanks for comments.

Currently my electricity bills are quite high. I have 2 areas that are heated by electricity plus we have a number of computers running 24h.

The 15 year payback is my target to justify installation.  I'm currently planning for early retirement and getting any large purchases out of the way

I've looked at storage. But I don't think it's cost effective yet. May look at this in future if technology gets cheaper.

Reason for say 6kw. I plan to buy eV in the next few years. How difficult is it to get permission  for 6k feed in or is possible to cap the feed in to grid but not cap to house.

arty688

You can have as much as your roof can take, it just the export to the grid that will be limited. Also think about any east or west roofs as this can extend the generation window south facing is not always the best.