Where do I start with solar panels and a battery install?

dharm999

https://forums.moneysavingexpert.com/discussion/comment/82112686#Comment_82112686

We only charge the EV a couple of times a month, as we have another car, not an EV, that gets used a bit more. Given IOG has a much higher standard rate, it doesn’t make sense to switch to it, yet. With solar panels, a battery, a switch to a heat pump and getting a second EV, it would be the sensible choice

Screwdriva

Welcome to the Green and Ethical sub forum!

If it isn't too much to ask, would you mind sharing:

1) An image of your roof? Google Earth snapshot is fine
2) Your annual electricity import (consumption) in KWh.
3) Any plans to get a heat pump?

From there, some of us will be able to give you a good steer.

dharm999

https://forums.moneysavingexpert.com/discussion/comment/82112645#Comment_82112645

Thanks. I’ve had a look at that, and am a little confused by it, to say the least. I’ve put a pin on my house. Then in the Installed peak power box, have put 4, I assume that means a 4kW install, so 10 400W panels. The system loss defaults to 14%, so I’ve left it as that. I’ve assumed a sloped roof install, and the website says just over 3508kWh of energy production. Changing to a flat roof install, I.e. freestanding, the figure increases to 3567kWh. Do these seem reasonable?

EricMears

https://forums.moneysavingexpert.com/discussion/comment/82112741#Comment_82112741

Even a couple of EV charges a month would qualify you for IOG.

And the 'real' benefit to you would be the ultra cheap overnight rate for keeping house batteries topped up when sunshine doesn't manage it..

dharm999

https://forums.moneysavingexpert.com/discussion/comment/82112744#Comment_82112744

Annual usage is around 6000kWh, include c600kWh for EV charging.

Plan is to get a heat pump that does cooling as well as heating, sometime in the next few years when current gas boiler gives up the ghost.

North is at the top of the image

dharm999

https://forums.moneysavingexpert.com/discussion/comment/82112785#Comment_82112785

At the moment the numbers don’t work financially to switch to IOG, because of the higher standard rate. Currently, under Agile I average around 20-21p per kWh, and that’s with switching tumble dryer and dishwasher to running overnight and charging the EV at low rates. But with solar panels and a battery the analysis would change and IOG may well be the better option.

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/82112755#Comment_82112755

Hiya. I think you've pretty much nailed it. I chucked a random pin in Leith and then in Portobello and for 1kWp south facing (zero azimuth) at 35d pitch I get ~900kWh pa, so ~3,600kWh for a 4kWp system. I got less than you for a flat roof (2,900kWh), but I expect you have (correctly) assumed a pitched install, so spot on again.

Teeny point, I understand that free standing is for most roof installs, the building integrated option is for when panels are in-roof (they replace roofing material).

I'd suggest leaving the default losses at 14%. It's actually a bit pessimistic now, but perhaps better to overachieve hopes/plans.

Also panel sizes and power can vary, but hopefully you'll be seeing around 480Wp these days for panels of roughly 1.1m by 1.8m, maybe 540Wp for around 2.1m by 1.1m.

Whilst the PVGIS figures are only guesstimates, and based on average months/years, they are extremely good, so you can feel confident using them, but do consider shading. Mild shading isn't that big an issue these days, but you mentioned trees for the south facing roof - so now might be a great time to see how much shading there is, through to late Dec when it will be worst. Don't worry too much about significant shading if it's only in the Dec/Jan period, even Nov-Feb, as generation will be low then anyway, and on cloudy days the panels will 'see' the daylight, if not the sunlight, so not all lost.

anselld

https://forums.moneysavingexpert.com/discussion/comment/82112727#Comment_82112727

Varies by region but where I am seems rarely below 20p anyway and do you really want to wait for the next short term dip to charge up?

dharm999

https://forums.moneysavingexpert.com/discussion/comment/82112827#Comment_82112827

As we have a second car, not an EV, we can pick and choose when the EV gets charged. The last few times have been when Agile rates were very low, or negative.

At the moment, our base load is 0.5kWH an hour, so 18 hours at 0.5kWh at 33p an hour gives a cost of around £3, and then 6kWh at 8p, gives an overall cost per day of around £3.50. Currently those 15kWh are costing me between £3 and £3.15 a day, and that’s with switching as much as we can to cheap overnight rates.

If we install a battery and solar panels then the dynamics change and it probably does make sense to switch to IOG

QrizB

I’ve assumed a sloped roof install, and the website says just over 3508kWh of energy production. Changing to a flat roof install, I.e. freestanding, the figure increases to 3567kWh. Do these seem reasonable?

"Freestanding" doesn't equate to a flat roof. For a flat roof you'd set the inclination angle to zero.

From the numbers you've quoted, I think your "freestanding" result is still inclined at maybe 40 degrees, ie. not flat.