Solar panels

mrtaylor79

Evening alll

i know the current FIT payments have ended, but are solar panels still a sensible investment?

I have 4 bedroom detached 3 of us in house occupied twenty four seven!! We also have a energy sapping hot tub that runs approx 9kwh per day! 

Martyn1981

Hiya and welcome. Such a short question, but such a big question too. Simplest answer is - it depends.

For best value, you want to go as big as possible/sensible, as PV gets much cheaper that way given all the fixed costs like labour, scaffolding, wiring etc etc, so if the roof (or rooves) is large enough for say 5kWp+ (around 25m2 useable) that would be a good start. 4 bed detached suggests we can tick that box.

Next, the more PV generation you use, the better the economics are, since you get paid relatively little for export, but reducing import saves a lot. Occupied 24/7, and hot tub, would appear to tick that box too.

So the million dollar question is how much. If you get a rip off quote for 5kWp of £10k, you might not see your money back. If you get a good quote of say £5k, then that would probably be OK.

Really rough guess at savings/income, if we assume 5kWp and a poor E/W orientation (like mine) then you'd hope to get 4,000kWh of generation per year, if you export half at say 4p (I've no idea what the potential is these days), and half is consumed against an import price of 15p (just a guess, refer to your bill), then you'll save/earn £380pa. A southerly orientation might be 5,000kWh and at a 50:50 split could be £450.

So it's roof size, location, orientation, generation, consumption and crucially cost ....... apart from that it's easy!

If you have a play with PVGIS and select your location, you will get a very good guesstimate of annual generation.

mrtaylor79

Hi there and thanks for your response it’s been extremely helpful and I only just saw this after I posted again(will take that down)

a while a go I had project solar out Just found their pack they sent me at time it was a £11k quote !  But importantly it was 35 pitch with s/e orientation 

I would happily consider at 5k! I am with octopus agile as of July . Think there feed in is 5.5kwh

Martyn1981

You have probably just sent half of MSE running for cover before 'Mart goes off on one' about Project Solar. Let's just say they get mentioned a lot on threads on here and never favourably. 

Sounds like you need to get some quotes now and see what they say. You will find loads of people on here will be more than happy to review prices and packages and share info and opinions.

Perhaps a read of older thread were there have been discussions going into all the minutiae.

Just for fun, I popped onto PVGIS, stuck a pin in the O of Oxford, changed the 1kWp to 5kWp, left the 35d pitch alone and entered -45 in the azimuth box (SE is -45d from south (south being the azimuth, point of interest)) and it suggested an annual generation of 4,660kWh. PVGIS is really good, though most of tend to get slightly better generation as the default losses of 14% it uses is a bit old and pessimistic these days.

mrtaylor79

So I’ve had quote of 14x ja solar 410 - hybrid 5kw inverter and GIv energy ac 8.2kwh cost is 5093.14 

then installation of £3395 - 

seems very steep in terms of expense install and much higher than previous quotes I’ve had 

oh and then there’s vat!

return they suggest 13 years estimate 

Martyn1981

Actually, I don't think that's too bad a price if (BIG IF) you also want battery storage, as that's 5.74kWp PV plus 8.2kWh storage, if I'm reading it right for ~£10k. Not cheap, but perhaps not too steep either as storage is expensive.
Can you get a PV only price from them, and worth checking if you have space for more panels, as you may find that 410Wp panels are disproportionately expensive, and having more (say 16) 350Wp(ish) panels might be cheaper?

mrtaylor79

Martin thank you so much for all your time and responses so it’s about 8900 I have said I’d like to get it under 8000 ideal 7500.

i am concerned in winter if I will utilise battery as I estimate the panels will only make 1-2kwh in a day. So I obviously need to Maximise during day - my plan is to utilise as much as I can at home and it would be a bonus if I my own usage meant nothing goes back to the grid.  

My driver for this is to reduce my home use currently roughly 20kwh per day, that’s due to a hot tub and I am being frugal with tub ! I have pot of cash in the bank that’s getting me no interest sitting there so thought I would use it for this but don’t want to pay over the odds I don’t think I can get anymore than 14 on roof 

pinnks

I think you are right about winter generation.  My expected daily average in November is about 3kWh; December 2kWh; and January a tad over 2kWh.  As noted below, my systems total 5.25kWp facing SSE and WSW. Your house's base load will pretty much gobble that up without worrying about maxing out on anything. 

mrtaylor79

pinnks said:

I think you are right about winter generation.  My expected daily average in November is about 3kWh; December 2kWh; and January a tad over 2kWh.  As noted below, my systems total 5.25kWp facing SSE and WSW. Your house's base load will pretty much gobble that up without worrying about maxing out on anything. 

Thanks so basically for that I can expect my house to basically use all of power without an export ? 

In terms of roi is there any point in getting system I’d like to really reduce my reliance on grid for home use during day and summer months so 7 months per day ! Is it possible to generate 20kwh from solar in a day?

Petriix

You will definitely export some electricity. 8kWp of panels might peak at 50kWh+ [5.74kWp of panels might peak at 40kWh+] of generation on the best days (although I'm not sure how much impact having a significantly low rated inverter might have on this). If you use 20kWh of that then the rest will go to the grid. Your battery will help you to avoid importing as much from the grid but won't eliminate export on days where your generation is greater than your consumption.

As you are a high user, you may fall into the small minority of people who will see a positive return on investment from a battery system. You need to do the sums though.

Typically it's difficult to (efficiently) use more than about 40% of your generation. A battery will allow you to use more of what you generate (up to 100% on days when you consume more than your generation) and draw less from the grid (reducing imports to 0 on days when your generation exceeds your consumption).

I use around 10 kWh per day. My 3.42kWp system generates an average of 11kWh per day and roughly half my demand is met by this, with the rest of my generation exported to the grid and the rest of my consumption imported. I estimate that I could reduce my average daily import by half with 5kWh of batteries (and diminishing savings above this size).

However, this would only reduce my bills by £115 per year. As batteries supposedly last around 10 years, they would need to cost less than £1150 to realistically break even for me.

Work it out for your own usage and see how the numbers stack up.

Martyn1981

Hiya Petrix, the PV would be 5.74kWp, it's the battery that is 8.2kWh.

Mr Taylor, for SE orientation, you will see peak days, probably May - August where you generate around 7kWh/kWp so about 40kWh (rough estimate). My systems average about 20kWh per day in those months, with actual generation typically around 15-30kWh (with the odd very low one on a rainy day.)

My December target is 79kWh, so about 2.5kWh/day, but being so off south, the gen collapses due to low angle of the sun not 'seeing' the panels.

Quick play on PVGIS, selecting York (you mentioned living in the NE?) for 5.74kWp, gives an estimate of 5,200kWh pa and the lowest month is December at 153kWh, call it 5kWh/day. Quick warning though, the bottom months (Nov - Jan) can vary a lot, especially with grey weather, so something like 60% of target is possible. PV is the greater leveler, you get good and bad days, months and years, but it tends to average itself out. My 8yrs of results have performed between 99% and 106% of PVGIS target, though this year is doing much better, possibly 109% if there isn't a terrible 2nd half to the year. So, over time, it's pretty boring and predictable.