EST Solar Calculator reliability?

controversy

Hi there. How reliable is the energy saving trust solar calculator compared to real experiences?

I have a roof facing south at 120* degrees East with a 45* degree inclination.

For a 4kw system the calculator says the KWH raised will be 2287.

I probably have the worst roof for solar panels but I am still willing to see if I can save some money.


What are current Solar Panel owners & users thoughts?

Martyn1981

Don't get me started!

And hi by the way.

I've moaned about their calculator on here a couple of times and rung them up to point out that the leccy savings part doesn't actually work, so there must be a problem with the calculator.

Quick comparison:

I've just tried the calculator again for my property. I used the details of my ESE system 110degress from north, or -70 azimuth from south, and a 30d pitch roof, but called it 4kWp (not 3.58 for simplicity).

The EST calculator suggests 3,081kWh pa,

but PVGIS (which most of us use and trust on here) suggests 3,420kWh. That's not too big a difference, but could be enough to put off folk with non-south systems, such as you describe, but at 120d your system will work fine, so long as you appreciate/accept that it won't be brilliant. [More on PVGIS later.]

Next the EST calculator suggests a leccy saving of £79, whereas I'd suggest a figure of £120 (£80 to £160). Now you could say they are just being conservative, fine ....... but if you click on the button to see how the calculations are made, they state a consumption of 25% at 13.52p/kWh ....... so let's try it:

3,081 * 0.25 * 13.52p = £104.14. Not £79?

I've complained to them twice since last summer that this part of the calculator is broken, but 6+ months on, nothing has happened!

Sorry for the rant, but you asked the perfect question to 'set me off' this morning.

Right, rant over, so now for the help and advice, have a read of the PV FAQ's section 1 & 2. Just a quick skim, then perhaps if it makes sense, start to go through some of the links to get a solid grasp.

Have a look at section 5 on PVGIS and have a go at working out your generation potential, or at least a good guesstimate of it.

Then pop straight back and ask a thousand questions, loads of PV'ers will be more than happy to help.

BTW, did you enter a shading figure into the EST calculator, as I've tried your info on PVGIS (120d from north, 45d roof) as far north as the top of Scotland, and it's still coming out much higher than 2287?

Mart.

tunnel

If you take a look at mine and Marts signatures you'll see that we have both installed "worst roof" installs.
Do your homework and take a little advice from the kind folk on this site, most will give straight forward advice including working out your generation(Mart).
If you post your rough location maybe someone local to you may offer a recommendation for a reliable, trustworthy installer that's not in the business to rip your eyes out(trust me its a mine field)


As Mart states, get some quotes and then ask away on here

controversy

Okay.

The PV potential estimation utility.

My roof goes 120 West North West -60 East South East.

The utility says East is -90 and South is 0. So that means West is 90 and North is 180.

I just found out my roof inclination is actually 36.8

I live in Lincolnshire Wolds at LN86ER or Lat 53.439 Long 0.192

On a 4k installation at -60 with zero system loss my KWH gain is 3950.

Have I done this correct?

Link for calculator.

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>

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

Martyn1981

controversy wrote: »

Okay.

On a 4k installation at -60 with zero system loss my KWH gain is 3950.

Have I done this correct?

Yes and no.

I've just checked and also got 3,950, but had to change the default losses from 14% to zero, as you mentioned.

I'd leave those losses at 14%. Some installers think they are a little high, but best to err on the side of caution whilst working out if this is a good investment (or not) for you.

Note - those aren't shading losses, they are the system losses, inverter efficiency, cable losses etc etc etc.

So any estimated shading needs to be deducted from the main figure, not the system losses box.

So putting the 14% back in, I get 3,390kWh, which is a pretty damn good figure, considering you're not due south, and slightly outside 'the SE to SW sweet zone'. Also a hell of a lot better than the 2,287 figure you got from the EST!

Now, assuming there is no shading, you can work out a reasonable estimate of income:

FiT 3,390 * 13.88p = £470
Export deemed at 50% of generation 1,695 * 4.77p = £80
Leccy savings (£80 to £160) = £120

Total £670

If you can get an install for less than £6k (hopefully nearer to £5k) then a decent return.

Mart.

controversy

Sounds good.

Are there any tracking systems which can shift panels left and right or up and down for roof mounted panels?

zeupater

controversy wrote: »

Sounds good.

Are there any tracking systems which can shift panels left and right or up and down for roof mounted panels?

Hi

Ground based trackers were a reasonable idea when pv panel prices were much higher but at today's prices aren't a cost effective option. You could change the orientation & angle on a decent flat roof (or ground mount) using angled framework, but on a standard pitched roof you would just create a condition where the panels would lift in high winds and simply rip your roof apart ....

If the roof has no shade don't worry about doing anything out-of-the-ordinary to maximise generation as it'll just add more cost than necessary ... if you need more generation & you've got money to burn you'd be better buying a bigger standard system (as long as it'll fit) ...

HTH
Z