Solar Panel Guide Discussion

silverwhistle

silverwhistle wrote: »

I'll be having to get new white goods

Plus an induction hob; just heard that the gas hob has been condemned!

Sirlaughalot

Martyn1981 wrote: »

Hello good Knight. I've had a go at some numbers for you, but obviously they are only guesses and estimates.

For a 4kWp install in Birmingham, west facing at 30d pitch, PVGIS estimates annual generation of 3,10kWhs.

Income streams will be approximately:
FIT 3,010 @ 14.9p (from 1/7/13) = £450
Export (50% deemed) 1,505 @ 4.64p = £70
Leccy savings (£80 to £150) = £110
Total £630


You'll need to hunt around for a good price, especially being west facing (about 20% less than south facing). Target prices were under £6k, but the Chinese tariff war is messing things up. But still aim for £6k.

A while back I slapped together a cheap spreadsheet to compare interest v's income.

Part 1 just looks at the cash savings account, with compound growth for 20 years.
Part 2 looks at the PV income, with inflation growth, and panel degradation.
Part 3 takes part 2, but assumes all income and leccy savings are re-invested, earning interest and compounded (as per pt1), and deducts money for a replacement inverter (from the running total) at year 12.

Interest rates are assumed at 3%, inflation at 3%, degradation at 0.5%, and replacement inverter at £1,200.

Entering £7k into part 1, and £630 into part 2 & 3 gives 20 year totals of:
P1 - £12,642.78
P2 - £16,068.86
P3 - £19,509.80

Entering £6k, gives a compounded 20 year total of £10,836.67.

Very basic, and admittedly I've not allowed for any maintenance, other than an inverter, as it's hard to know if or what there will be. But in exchange I've also ignored PV income/savings from years 21 onwards, after the FIT has ended, hopefully the panels will work for 30 years or more, but by year 20 may be down to 80% to 90% efficiency.

Mart.

Great post Mart.

Not sure if i would get any electric use out of them as were at work all day.
Cheers as i forgot the reinvestment value of the fit and export. Looks like our area of Birmingham is not the best for solar panels as i can`t see many around our estate. Perhaps if i can drive down the initial outlay by buying the panels direct it would look more viable.

Thanks for your help

Martyn1981

Sirlaughalot wrote: »

Great post Mart.

Not sure if i would get any electric use out of them as were at work all day.
Cheers as i forgot the reinvestment value of the fit and export. Looks like our area of Birmingham is not the best for solar panels as i can`t see many around our estate. Perhaps if i can drive down the initial outlay by buying the panels direct it would look more viable.

Thanks for your help

My pleasure, glad to help. Quick run through:

Leccy savings, to get the most from the system you'll want to try to run some devices during the day, for a West install, probably from around 1 or 2pm onwards. If you can't set stuff on timers, then you won't benefit as much during working days. But you will save when home (weekends / days off ?). Also baseload should be covered when the sun's out. If you're unsure then go to the bottom end of the estimate or even lower, perhaps £70 pa or so.

Why no PV? Hard to tell, it seems to go in batches, maybe neighbours copy neighbours. My roof(s) isn't ideal (see signature) and the nearest PV to me, is about 50 houses away, and equally 'iffy', yet there are loads of really good roofs. Lots of people ask me about PV, but I think they are very scared of this new 'magic technology'. The key is to have a nose on PVGIS for your area to establish a generation figure, then have a look around to assess any shading.

Buying direct. If you mean getting the kit, then arranging an installer, couple of problems. You'll have to pay 20% VAT, but an installer will only pay 5%, plus they'll probably have preferred kit and suppliers.

You might find that the installers are a bit quiet from next week, as there has been a bit of a burst to meet (avoid) the new tariff (1/7/13). So you might get better quotes, or rather, be able to haggle down a bit. If you do decide to investigate, tell any installers that as it's off-south, and about 20% less generation, you simply have to get a good deal, or not worth doing. This isn't haggling, just a honest friendly chat - cards on the table stuff!

If your roof is big enough for 4kWp, then I think you need to aim for £6k (or less).

Take your time and have a think.

Mart.

Sirlaughalot

Martyn1981 wrote: »

My pleasure, glad to help. Quick run through:

Leccy savings, to get the most from the system you'll want to try to run some devices during the day, for a West install, probably from around 1 or 2pm onwards. If you can't set stuff on timers, then you won't benefit as much during working days. But you will save when home (weekends / days off ?). Also baseload should be covered when the sun's out. If you're unsure then go to the bottom end of the estimate or even lower, perhaps £70 pa or so.

Why no PV? Hard to tell, it seems to go in batches, maybe neighbours copy neighbours. My roof(s) isn't ideal (see signature) and the nearest PV to me, is about 50 houses away, and equally 'iffy', yet there are loads of really good roofs. Lots of people ask me about PV, but I think they are very scared of this new 'magic technology'. The key is to have a nose on PVGIS for your area to establish a generation figure, then have a look around to assess any shading.

Buying direct. If you mean getting the kit, then arranging an installer, couple of problems. You'll have to pay 20% VAT, but an installer will only pay 5%, plus they'll probably have preferred kit and suppliers.

You might find that the installers are a bit quiet from next week, as there has been a bit of a burst to meet (avoid) the new tariff (1/7/13). So you might get better quotes, or rather, be able to haggle down a bit. If you do decide to investigate, tell any installers that as it's off-south, and about 20% less generation, you simply have to get a good deal, or not worth doing. This isn't haggling, just a honest friendly chat - cards on the table stuff!

If your roof is big enough for 4kWp, then I think you need to aim for £6k (or less).

Take your time and have a think.

Mart.

I`m sure our roof is big enough for 4kWP when you buy the panels direct i assume you are able to get the inverter and meter from the same place as well. Is the power generated between 2/3 pm sufficent to power a washer dryer and perhaps a 3kw ceramic heater?

Many thanks

EricMears

Sirlaughalot wrote: »

when you buy the panels direct i assume you are able to get the inverter and meter from the same place as well.

I'm sure you could buy all the bits quite easily. BUT unless you're registered with the correct authorities you won't be able to sign off your installation and claim FIT payments. And, as Martin mentioned earlier, a registered solar installer gets to pay 5% vat on panels and can charge you 5% on whole job. Without that registration, an electrical wholesaler would have to charge you 20% vat.

John_Pierpoint

A picture is worth a thousand words, if you check out a poster called shafeeq, he is talking about the shading of his installation and the problems its causes throughout the seasons.

https://forums.moneysavingexpert.com/discussion/comment/61739717#Comment_61739717

If you can post pictures of us looking at your roof and your roof looking east south and west, we could advise on points to raise with the salesman. The rest of the house and the plot would be interesting but an invasion of your privacy and not really relevant, provided shading and features such as chimneys are visible.

http://www.pistonheads.com/gassing/topic.asp?t=987738

[Having a real chimney, even when it is used by a log burner, reduces Britain's chances of meeting the EU targets for zero carbon homes and carbon emission targets, as measured by the compulsory Energy Performance Certificate].

Martyn1981

Sirlaughalot wrote: »

Is the power generated between 2/3 pm sufficent to power a washer dryer and perhaps a 3kw ceramic heater?

Many thanks

Sorry SL, this comes under 'how long is a piece of string'. A 4kWp system might sustain 80% to 90% (they drop off as the panels get hot) in good weather so 3.2kW to 3.6kW. But under solid white cloud, perhaps 500W, under a dark grey/black sky 0W.

If you have an alternative, such as economy 7, then you'd need to gauge the weather and decide which is better, running at night, or using a timer to switch appliance on in afternoon. If you have no alternative, and have to run the appliance, then any contribution (large or small) from the PV will reduce consumption.

Also baseload savings are tricky to estimate. Currently my 3.6kWp ESE system is generating 1,510W, but my 2kWp WNW is only generating 141W. This bit is so unscientific it is almost meaningless (as panels not in the sun, generate depending on level of reflection from the sky/clouds) but scaling that up to 4kWp would mean approx 282W helping to off-set baseload.

My baseload is about 200W but varies as fridge and freezer cycle, but off-setting baseload for 16 hours (5am to 9pm with E & W panels) could save 3.2kWh. Bad weather will be less, and winter hours could be 6hrs (9am to 3pm) not 16.

The key trick with PV is to try to utilise it by spreading demand out over time. If you have 3kW of generation and want to run 3 2kW items for an hour each, then running one at a time means PV could cover all of them - 3kW gen, 2kW demand for 3hrs. But if you ran all 3 at the same time, you'd have 3kW supply and 6kW demand for 1hr. You'll never get this 100% right, but the idea is just to increase your chances of using more PV and less import.

Can I ask another question, what pitch is your roof? This might be important. For a south facing roof, pitch isn't too important, shallow roofs generate better in the summer, steep in the winter, but annual totals don't vary too much. But for E or W roofs shallow pitches are better, since the sun doesn't reach them in the winter when a steep pitch (to match shallow sun angle) is better.

Mart.

Sirlaughalot

Martyn1981 wrote: »

Sorry SL, this comes under 'how long is a piece of string'. A 4kWp system might sustain 80% to 90% (they drop off as the panels get hot) in good weather so 3.2kW to 3.6kW. But under solid white cloud, perhaps 500W, under a dark grey/black sky 0W.

If you have an alternative, such as economy 7, then you'd need to gauge the weather and decide which is better, running at night, or using a timer to switch appliance on in afternoon. If you have no alternative, and have to run the appliance, then any contribution (large or small) from the PV will reduce consumption.

Also baseload savings are tricky to estimate. Currently my 3.6kWp ESE system is generating 1,510W, but my 2kWp WNW is only generating 141W. This bit is so unscientific it is almost meaningless (as panels not in the sun, generate depending on level of reflection from the sky/clouds) but scaling that up to 4kWp would mean approx 282W helping to off-set baseload.

My baseload is about 200W but varies as fridge and freezer cycle, but off-setting baseload for 16 hours (5am to 9pm with E & W panels) could save 3.2kWh. Bad weather will be less, and winter hours could be 6hrs (9am to 3pm) not 16.

The key trick with PV is to try to utilise it by spreading demand out over time. If you have 3kW of generation and want to run 3 2kW items for an hour each, then running one at a time means PV could cover all of them - 3kW gen, 2kW demand for 3hrs. But if you ran all 3 at the same time, you'd have 3kW supply and 6kW demand for 1hr. You'll never get this 100% right, but the idea is just to increase your chances of using more PV and less import.

Can I ask another question, what pitch is your roof? This might be important. For a south facing roof, pitch isn't too important, shallow roofs generate better in the summer, steep in the winter, but annual totals don't vary too much. But for E or W roofs shallow pitches are better, since the sun doesn't reach them in the winter when a steep pitch (to match shallow sun angle) is better.

Mart.

Hi Mart,

Don`t really want to second guess the british summer lets face it the BBC daily weather reports seem to get it as wrong as many times as they get it right! Think you could end up with burn`t fingers so daily savings will be based on fridge/freezer use and washing machine/dryer use and of coarse weekends and holidays.

Assuming i have this right the sun rises in the east and sets in the west the best roof i can use in terms of shading is a ENE facing roof at a pitch of 30 - 40 degrees

Oscargrouch

what_the_.... wrote: »

Hi,
Has anyone any experience of conergy pv solar panels and Hyundai solar panels, the reason I ask is that there is a two grand difference in price, the salesman for the conergy ones said they will generate 3400kwh and not to touch Chinese or Korean ones because the EU will come back looking for import tax, can this be right ?. the chap selling the Hyundai ones said no panels in our area will generate more than 3100kwh maybe 3200kwh on a good year. what do you guys and gals think ?.( area is southern Scotland)

Mart knows what he is talking about. You may be interested in reading a page or two from this link onwards...
https://forums.moneysavingexpert.com/discussion/comment/57301951#Comment_57301951

And...perhaps this; just put in your own address....
http://www.suncalc.net/#/52.4862,-1.8904,10/2013.01.01/10:09

Martyn1981

Sirlaughalot wrote: »

Hi Mart,

Don`t really want to second guess the british summer lets face it the BBC daily weather reports seem to get it as wrong as they get it right. Think you could end up with burn`t fingers so daily savings will be based on fridge/freezer use and washing machine/dryer use and of coarse weekends and holidays.

Hello SL. Sorry, didn't realise what the ceramic heater bit meant. If you were thinking about leaving something on (that is optional) then burnt fingers are very likely. get it wrong and you're importing expensive leccy. There are devices, talked about on other threads, like this one:

https://forums.moneysavingexpert.com/discussion/4152489

that can direct excess generation via proportional controls, but you'll need to do some maths to see if they'll be financially viable for you.

Sirlaughalot wrote: »

Assuming i have this right the sun rises in the east and sets in the west the best roof i can use in terms of shading is a ENE facing roof at a pitch of 30 - 40 degrees

Quick check again using PVGIS (I strongly recommend you have a play). Stuck a random pin in Birmingham, 4kWp and azimuth -110deg. [The azimuth is your point of interest, which for us is the sun, to the south, so before it is a minus, east is -90, and after it is a plus, west is +90.] ENE is approx -110.

Then tried a selection of roof pitches. 20d gave annual generation of 2,900kWh's. 50d was 2,420. So big difference. But 30 to 40 not so bad - 30d was 2,750, 35d was 2,680 and 40d was 2,600.

Shading is important, and there are ways to reduce the effect, but you can't eliminate it. Also, not ideal to install anywhere with a 'N' in it. Ignore my WNW, it is extremely marginal, and was to maximise generation, not income. For the same 'pin' location as above, PVGIS gives 3,730 for due south at 35d pitch, so ENE is a big drop, and will affect your returns significantly.

Ok, serious danger of me flooding you with too much info now (too late perhaps!). So I'll stop. But ask anything, happy to help. Also there are probably lots of old threads that cover many of the issues - but you might need directions to particular posts, on particular threads.

Your best bet, if you're still interested, might be to arrange for a few installers to pop round and assess your situation. You'll learn loads, and get a better idea on prices.

Mart.