Forum newbie & home worker needs advice re solar panels

marchesini46

Hi all,
I’ve been inundated with calls re solar panels and have tentatively looked into the subject in the past.

However, with my electricity bills increasing at a quicker rate than Greece’s national debt, I’ve recently been looking at reducing them where I can. I put energy saving bulbs in where I can and installed an electricity monitor so I have more of an understanding of what is using the most power.

Anyway, onto the point of my post. I am extending my house and I have a (relatively) south facing roof - which I understand is a good starting point for solar panels. From my (limited) research, I’m best paying for the panels up front and going for a 16 panel 4kWh system. Not sure what brand etc but should be looking to spend around £5-6K max.

I work from home most of the time on laptops etc so will be able to make use of the ’free’ daylight electricity. In addition to this, if I ensure that the washing machine and tumble dryers are only used during daylight hours, would I be expected to make larger savings than normal - we do a lot of washing with two footballing boys. I have seen some figures quotes as 15% off your electric bill which doesn’t sound massive but wondered whether I could expect bigger savings - bearing in mind my circumstances.

For the record, my yearly usage is 8627 kWh which I believe is quite high. Is there an online calculator that give realistic expected savings or do you just have to get a pen & paper out to give you a real-world figure?

Lastly, as I work from home, I can offset a proportion of my energy bill as business use so am I better served just ignoring the solar power ‘benefits’ and putting the 5K towards a more efficient boiler (or something which will give me more bang for my buck).

Many thanks in advance for any insights you can give me.

Simon

Martyn1981

marchesini46 wrote: »

Hi all,
I’ve been inundated with calls re solar panels and have tentatively looked into the subject in the past.

Simon

Hiya Simon. So you've been worn down then!

Firstly, good post, loads of info, and you do tick all the PV boxes. Good orientation, high leccy use (more potential for savings), daytime use (even more potential), and a good basic understanding of what would be nice to install, and the better end of the price range.

If you have a read of section 1 of the PV FAQ's, you'll get an idea of the income streams for PV.

I'm always a little wary of misleading folk with 'too' high leccy savings, but I think it's OK to say in your circumstances that you'll most likely do better than £120. You may find an on-line calculator, but there are too many variables - size and time of generation, size of import, daytime use, effort put in etc.

If you don't mind giving an approx location (nearest town/city) and your roof orientation (as "relatively south facing" could be SE to SW, which may affect generation by 10%) I'll happily play with PVGIS (section 5 of the FAQs) for you, and give you an income breakdown guesstimate. Have a try yourself, it's pretty straightforward.

Regarding the 15% of your bill, this gets a little complicated. Some companies say you'll use 50% of what you generate (that's too high for most). Then there's a percentage of what you import, I cut mine by almost 50%. Then there's a percentage of your bill, which differs again, as there will most likely be a standing charge element, so my bill hasn't fallen 50% in £'s, despite falling 50% in kWhs.

Funnily enough, 15% might not be far off. I'm plucking numbers out of the air here, but if you had a 4kWp system, and generated 3,800kWhs. Then managed to use a decent 40%, that would be 1,520kWh. 1520/8627 = 17.6%. Taking S/C into account may mean 15% saving. Still, 1,520kWh would still be a very decent saving. [Note: made up guesstimate.]

Regarding your expenses, if you claim back your costs, and your costs go down, then you'll be no worse (or better) off. But I get your point that you wouldn't benefit from those units that you've invested money to generate. Kind of cheeky, but could you still bill for energy used, since instead of buying the units from your leccy supplier, you'd now be buying them from yourself during PV generation? Thin ice springs to mind here!

Mart.

tunnel

If you have been working from home for a few years then you know how much energy that your business uses. I'd be inclined to keep claiming that much as the tax man has obviously already ok'd it from previous years. You would still be claiming the expense without panels wouldn't you? I'm not advising you to do it as like Mart says its definitely a grey area, it's just my personal take on it.


As for panels, you're definitely in the right ball park with the £5-£6k, better looking at the lower end as it seems quite easily achievable for a standard installation.


Talking of standard, does/will(extension) your roof suffer from any sort of shading? It matters and you'll be well advised on here if it does/will.


Start with your rough location like Mart asked and you'll get some figures thrown back at you for the sort of returns you should achieve.


T

EricMears

marchesini46 wrote: »

For the record, my yearly usage is 8627 kWh which I believe is quite high. Is there an online calculator that give realistic expected savings or do you just have to get a pen & paper out to give you a real-world figure?

Afraid I've no idea of any reliable source for forecasting potential sayings but my own experience might be of some help.

FWIW, our annual electricity consumption averaged over 2009-2011 was 8030kWh (5350 Day units + 2680 E7).

For the period 30/6/14 - 30/6/15, we bought 2335 Day units and 1525 E7 units (total 3860) and generated 3818 units.

Fitting SPs in Aug 2011 has obviously helped a lot but no doubt regular meter reading (I only have quarterly bills before Aug 2011 and many of them were estimates. It was a real struggle to find two real sets two years apart !), switching from fluorescent tubes to LEDs in kitchen, halogen GU10s to LED versions in a couple of rooms and replacing a fridge/freezer and a washing machine have helped a lot.

Using a high proportion of our own generation (but I've no accurate estimate of that) is down to being at home most of day and switching major appliance usage from E7 (still used in winter of course) to peak generation times.

I've recently fitted an Immersun unit so should have a better idea of our proportion of generation usage next year.

silverwhistle

marchesini46 wrote: »

For the record, my yearly usage is 8627 kWh which I believe is quite high.

Ooof, it seems high to me but I'm single, work from home (occasionally) and as a veteran woman footballer do a fair bit of washing too!;-)

My annual bought in usage is <1100kWh which makes it worthwhile for me to have a standing charge free tariff. I divert excess power to an immersion tank and don't use the gas boiler for 6+ months a year. My Owl monitor under-reads generation, if the export figure is under-reading too then I export 40%, if the export figure is correct then I'm exporting c.36%.

I suspect you'll be able to cut your bill more than I can!

marchesini46

Martyn1981 wrote: »

Hiya Simon. So you've been worn down then! .

LOL. The phone calls are a constant reminder for me but experience has shown me the last place I ever want to get cost effective advice from is a cold calling phone salesman. It at least prompted me to do some of my own research.

Martyn1981 wrote: »

If you don't mind giving an approx location (nearest town/city) and your roof orientation (as "relatively south facing" could be SE to SW, which may affect generation by 10%) I'll happily play with PVGIS (section 5 of the FAQs) for you, and give you an income breakdown guesstimate. Have a try yourself, it's pretty straightforward.

My location is Barnehurst / Bexleyheath DA7 6HA so pretty far south. I tried to share a flick link to a screenshot but as a new user, I'm not allowed to do it.

S

marchesini46

silverwhistle wrote: »

My annual bought in usage is <1100kWh which makes it worthwhile for me to have a standing charge free tariff. I divert excess power to an immersion tank and don't use the gas boiler for 6+ months a year.

I presently use a combi boiler but am looking at adding a small boiler to look after the new extension and to make the house run more efficiently. The original house was a bungalow but has been extended several times so the pipework is not the most efficient. It can take a good 90 seconds of running a tap to get any semblance of warmth from the hot water tap in the kitchen. Not very efficient if all you want to do is wash a single cup. Presently looking at pressurised hot water cylinders to reduce the reliance on the combi so IF I could use excess generated electricity to heat the water that can then be stored for later use, that would be very cool. I am however, less knowledgable on the boiler options than I am with the solar options at present. One thing at a time I think or else my head will explode with facts and figures!

Martyn1981

marchesini46 wrote: »

LOL. The phone calls are a constant reminder for me but experience has shown me the last place I ever want to get cost effective advice from is a cold calling phone salesman. It at least prompted me to do some of my own research.

My location is Barnehurst / Bexleyheath DA7 6HA so pretty far south. I tried to share a flick link to a screenshot but as a new user, I'm not allowed to do it.

S

Well done, avoid the cold callers. They seem to work like a boiler room, feeding links to salesmen. These companies are getting away with murder, £7k, £8k, £10k installs! :mad:

Okey dokey, I opened PVGIS and stuck a pin in your postcode, all I've changed was the "installed peak PV power", replacing "1" with "4" for a 4kWp system.

If your roof isn't due south, or 35d pitch, then just change those too, for better accuracy.

The result was excellent, 4,120kWh pa.

So, income streams:-

FiT 4,120 @ 12.92p = £532
Export (deemed at 50%) 2,060 @ 4.85p = £100
Leccy savings, normally I suggest £120 (£80 to £160), but in your case, I think it'll be over £160, perhaps £200, but let's go £160 just in case.

Total £532+£100+£160 = £792.

If you are SE or SW, then perhaps 10% less, so £700(ish).

Not sure how expensive London is, but most of us on here would normally suggest aiming for £5k, certainly under £6k for most locations in the UK.

Mart.

marchesini46

Martyn1981 wrote: »

So, income streams:-

FiT 4,120 @ 12.92p = £532
Export (deemed at 50%) 2,060 @ 4.85p = £100
Leccy savings, normally I suggest £120 (£80 to £160), but in your case, I think it'll be over £160, perhaps £200, but let's go £160 just in case.

Total £532+£100+£160 = £792.

If you are SE or SW, then perhaps 10% less, so £700(ish).

Silly mathematics question then. If my regular annual electric bill is approx £1400 per year, does that mean I deduct the £700 income stream and save 50% off my electric bills? Or have I misunderstood something here ?

marchesini46

tunnel wrote: »

Talking of standard, does/will(extension) your roof suffer from any sort of shading? It matters and you'll be well advised on here if it does/will.

No shading until well after 4pm. In the absence of being able to show a picture or post a aerial image of the house location, I would estimate that the roof faces approx 10 degrees off due south (towards the east) - if that makes sense??

Martyn1981

marchesini46 wrote: »

Silly mathematics question then. If my regular annual electric bill is approx £1400 per year, does that mean I deduct the £700 income stream and save 50% off my electric bills? Or have I misunderstood something here ?

Nope. You submit generation meter readings every 3 months, and get paid the FiT and export based on those readings.

If you were to consume (for example) 1,500kWh's of what you generate, then your leccy bill would naturally be 1,500kWh's less.

So you get FiT and export paid to you, and leccy savings in the form of a lower bill.

But, if the incomes streams do add up to £700, and you mentally net that off against your current £1,400 bill, then I suppose, the net effect is, in a sense, a halving off your bill.

Mart.