Plug in solar

HillStreetBlues

Not something I've ever looked into knowledge is totally lacking, when it says Max 800W what does that mean for the user?

Netexporter

Yes, 800W is the maximum you'd get under ideal conditions ie. not all that often. And if you don't use it all the remainder will escape into the grid.

HillStreetBlues

https://forums.moneysavingexpert.com/discussion/comment/81934749#Comment_81934749

What does 800W mean?

Netexporter

0.8kW. It would probably cover your background daytime usage for about 8 months of the year.

HillStreetBlues

https://forums.moneysavingexpert.com/discussion/comment/81934766#Comment_81934766

Going for basic, would that mean if I used it for an hour and it generated at max capacity it would save 0.8 of a unit?

Netexporter

Yes. It's relatively trivial but as they say in Germany, where it is used en masse, every Lidl helps. It's more a feel good gesture than a money making enterprise.

QrizB

https://forums.moneysavingexpert.com/discussion/comment/81934776#Comment_81934776

Yes, in essence.

This assumes you fit a 800 watt system and that it's actually generating 800 watts for that complete hour. And that you don't have an added battery or smarts. All those things could make the situation better or worse.

QrizB

Just to give an idea, here's what the EU's PVGIS model predicts the typical annual output would be for an 800 watt plugin solar PV system installed in the central south (Swindon), pointing south with a clear horizon and inclined at 35 degrees to the horizontal.

You can see it's generating just over 800 kWh per year, with monthly highs close to 100 kWh in May to July and a low of about 30 kWh in December. It would generate more if you were at home and were able to move your panels 2-3 times a day to follow the sun throuh the sky, but that's not really practicable for most people.

If you manage to use half of that to replace electricity that you'd otherwise have bought from the grid at 25p/kWh, and don't receive any payment at all for the excess that you export, you'll save about £100 a year.

Lidl in Germany were selling 800 watt systems for 250 Euros (about £220) when they had a promotion earlier this week, so you could be in profit early in the third year.

("Use half" is quite an optimistic target for a larger system; most folk with 2kW or more seem to use about a third if they don't have a battery or hot water diverter. But for a small system, I think using half is a reasonable goal.)

Netexporter

https://forums.moneysavingexpert.com/discussion/comment/81934800#Comment_81934800

What happens at 90 degrees (balcony mode)?

QrizB

What happens at 90 degrees (balcony mode)?

With the same system and an inclination of 90 degrees (vertical) you get this:

So quite a lot less output in total (about 600 kWh), but a flatter curve through the year and usefully more generation in the winter months.

At the other extreme, with an inclination of 0 (ie. laid flat) there's this:

Slightly more in the height of summer (more than 100 kWh a month at the peak) but less overall (almost 700 kWh) and terrible winter perforance.

The PVGIS model is free for anyone to use, so if you want to try adjusting settings (eg. if you don't live in Swindon) please give it a whirl!