Help comparing proposals

[Algarve_Martin]

Hi,

We want to install photovoltaics at our house in the Algarve and I have received a few offers I need input to compare.

We have 3-phasic supply, a roof with 20 degree inclination to SW and very little shading and are looking at a system without battery storage. Our consumption is about 12000kWh/year.

A local company offers a system with 18x347Wp panels, 6.0kW RCT inverter and new electricity counter, all installed for €12,127.-. This is similar to the first offer I got.

An electricity supplier (Endesa) has on their website a 20x340Wp panel system with microinverters, all installed, for €8,280.-. Endesa even has an option of interest free payments over 3 years.

To me this looks like a huge difference for very similar capacity systems, can there be something hidden here?

Here in Portugal, we pay something like €0.18/kWh for electricity and feed-in tariff is €0.04-0.05 as far as I have learned.

You comments?

Thanks, Martin

Background details:
Algarve is in southern Portugal, climate is similar to central California but I think sunnier with over 3000hours/year.
Electricity grid is 3-phase 400V (so 230V per phase) and quite reliable, I think we have had less than 30min total outage since we move in late September.
We already have thermal solar for hot water.

[Mike90250]

remember with micro inverters - they are up on the roof, sheltered only by the solar PV panel. They get hot & cold every day, That thermal swing is hard on electronics.

A wall mounted inverter at ground level is more vulnerable to theft, but is way easier to replace if it goes bad - there is only one to have to locate and replace.

Actual PV panels seldom go bad, but I'd get a spare or two, to have on hand. Getting a replacement in 4 years, that fits the same mounting holes, is going to be tough

[Algarve_Martin]

Thanks, I can see the thing about thermal swings. ATOH, wall mounted inverters also seem to have a shorter lifetime than the panels (I've seen ~10 years).

What I find appealing by the system with micro inverters is that if the rules change making sale of power more attractive, it would be easier to expand. And then it looks like the brice is a third lower for the same capacity, still waiting for an actual proposal.

[GTAZ]

I don't know about prices in Europe, but when I've researched costs in the US, Micro inverter systems can cost more if you ever want to add any kind of backup/off grid/grid down capacity. Then you need to buy charge controllers, and additional inverters, and battery management, and it means converting from AC out of the microcontrollers back to DC to charge the batteries, and then back to AC for loads. Micro inverters are best for installations that are ONLY grid tie. In a small grid tie they can be cost effective, but in a larger grid tie system they can cost more than a single inverter.

As for theft, well, don't mount it outside on the wall. Mount it inside. It also reduces temperature swings on the device.

[Algarve_Martin]

I was also surmised about the pricing, but let then do the actual proposal - perhaps that is different from the website (which is a bit light).

Reliability of the grid is quite good here, I think we have been without mains for less than half an hour total since we moved in late September - it has blipped enough to restart the WiFi a couple of times. Financially it does not make sense with batteries from the suggestions I have seen, and environmentally even less. This of course could change in the future.

We have a good wall in the laundry for mounting if needed, with a fusebox for the borehole pump right next to.