The Accidental Smallholder Forum

Smallholding => Renewables => Topic started by: alang on November 04, 2018, 03:18:08 pm

Title: Payback timescales for solar
Post by: alang on November 04, 2018, 03:18:08 pm
So we've just done the price comparison thingy to see how much our bill is  going to change now that our fixed tarrif is running out and our bill is going to be going up  to 65 a month!

I've been interested in solar electric power forages and was just wondering roughly what the payback period is like for solar. I understand there are a lot of variables involved such as size or system, weather and initial costs but trying to get a starting figure for the initial costs is a nightmare to even start to work things out.

I gather a standard system is 4Kw? I have a SW facing roof which has an angle between 30 and 45 degrees of more than 10m square. There are no trees or shade on the roof during normal daylight hours. Is a 4Kw system ok or could i get smaller/bigger one?

Sorry if this all seems a bit basic or disjointed but, the whole thing has got me a bit confused when i've read things on the net about it.
Title: Re: Payback timescales for solar
Post by: pharnorth on November 04, 2018, 07:00:24 pm
There should be a few companies about that will give you a quote and will also give you their forecasts on pay back time. 4kw is fine for a normal household we went for 7.5 and put it on the barn roof. Payback time we estimated at 9 years. So it was an excellent pre retirement investment.  Of course some grumble tariffs are lower than they were, but they somewhat mirror the installation costs so as hardware has got cheaper, tariffs have reduced.  Anyway, it is somewhat irrelevant that someone may have got a better deal a decade ago, it is more relevant to consider if it is a good deal now.
Title: Re: Payback timescales for solar
Post by: cloddopper on November 15, 2018, 10:36:10 am
Our roof is orientated the same as yours. We paid 2300 for our 16 panel 4KW hr system & had it installed on 30 & 3 Jan 2014 , according to the figures worked out by the power wall sales man using on line  rates of generation he reckoned our system had an overall out put that was 18 % above the average for the area . So using his figures 
our panels are well paid for and we are now in to profit  .
( we clean the panels on the bungalow with de ionized water & a spray of one squeeze per gallon soapy fairy liquid water  twice a year )

 Going by his figures we paid for the system about 20 months earlier than the estimated payback period  when we took the decision to install it at the 17 .5 p FIT.

 Having our dish washer , dryer , washing machine and car charger on their integral time clocks & using manual over rides has allowed us to  take maximum advantage of the whole set up .
  Some folks reccommend using more panels to take advantage of low energy generating conditions .. One guy I know has 20 panels tied down to a 4 KW hr  inverter by what he's told me  , it seems  his average fullfilled generation is way higher than mine .
Title: Re: Payback timescales for solar
Post by: DavidandCollette on November 15, 2018, 01:06:53 pm
I read recently that as of April next year new systems will still feed into the grid but there will be no payment back. Anyone know if this is correct?
Also if you are off grid what happens to the excess electricity produced? Never was any good at technical  ::)
Title: Re: Payback timescales for solar
Post by: regen on September 12, 2019, 08:11:00 pm
 "We paid 2300 for our 16 panel 4KW hr system & had it installed on 30 & 3 Jan 2014"

That is a competitive price-care to name the company
Title: Re: Payback timescales for solar
Post by: cloddopper on September 22, 2019, 11:20:19 pm
Regen ..
 Just been reading back on the  solar PV production thread ,  the install price  I gave was wrong ... it should be  5, 200 (  :-[ Idon't know where the 2300 price came from  :excited:  I claim dyslexxia )

Like many of the solar install companies with only five or six installers they have gone with the wind when the bottom fell out of the FIT's two or three years ago .

IIRC...  it was a local company from Cross hands Llanelli, with the welsh for " renewable energy "
Title: Re: Payback timescales for solar
Post by: regen on September 24, 2019, 06:01:13 am
that makes sense now. I paid 5500 for 4kw in Norfolk in March 2015 and that system has averaged 4250kwh PA but our ground mount in carmarthenshire,installed in 2011 at 3x the price only manages 3650 and has just finished paying back the capital.
Title: Re: Payback timescales for solar
Post by: cloddopper on September 29, 2019, 07:17:16 pm
Around the beginning of August I sprayed my panels with a strong solution of Fairy green  treated water one day when it was damp .
 Left it a few min then agitated it with a 7 mtr long soft window cleaning brush , washed it off with a spray jet hose  let it drain clean , found a few bits I'd missed re treated them and  found the flashing rate on the meter had almost doubled to one flash every second & a half .
Have you cleaned your Welsh panels yet ?   I was surprised at the amount of green algae that had formed on them , the clue to me was seeing the green on the ends of the panels as I looked up from the ground to the roof's apex . Everything is now as clean looking as the day they were installed including all the visible side edges ..
Title: Re: Payback timescales for solar
Post by: regen on September 30, 2019, 06:03:33 am
Makes sense to clean them if accessible but jury seems to be out on how much it improves efficiency and unless very dirty only makes economic sense if DIY. Any improvement noted on a before and after senerio may be mainly due to lower panel temps rather than the effect of cleaning.


My ground mount panels on a south facing slope have only been cleaned by the rain during the last 8 years with no apparent fall off in annual efficiency but they do not suffer from bird droppings or a build up of green algae so often seen in west wales.
Title: Re: Payback timescales for solar
Post by: cloddopper on October 01, 2019, 08:59:50 pm
Regen you mentioned temperature  wrt generation . Do you know if the panels have a , " Goldilocks  temperature  range"  where if it is just right you get maximum generation efficiency ?
Title: Re: Payback timescales for solar
Post by: regen on October 02, 2019, 12:07:05 pm
No idea really but the 3.96kw of panels regularly max out at 3.608kwh any time from march to june but very rarely,even in full sun,in july and august when the ambient is higher, often maxing out around3.0kwhAs 3.608 is the max permitted by DNO then they do their job apart from the 2/3 hot months.

In Norfolk there are 3.92kw of panels and the installer forgot/did not know how to set the maximum at 3.6 and in the cooler months they often exceed 4.1kwh but have not seen more than about 3.5kwh in july/aug.
Title: Re: Payback timescales for solar
Post by: cloddopper on October 02, 2019, 03:58:02 pm
Thanks.