Making the jump to solar

[GaryMG4]

Some interesting quotes there. Have you got quotes from other companies too?

With only 8 panels you'd be under using a 5kWh inverter meaning it's be less efficient. Is 8 panels the maximum you can fit of your roof? What's your years usage ? which battery would cover a full day usage?

Surely in that case every inverter would be inefficient as they are rarely fed with the full capacity of the panels, and I'd guess they would be hybrid so DC-DC to the batteries?

 

[Everest]

Right guys got some figures to digest and some questions ,
5kw battery or 10kw battery , which would you recommend

No one ever complained about having too much battery storage

In addition to what @MattyS asked, have you done an energy audit to determine your peak power usage. From my experience, these days, I'd avoid only having a 3.6kW inverter - you will exceed its output capability as soon as your turn on two high-power devices (e.g. kettle and toaster). So minimum of 5kW inverter would be my suggestion.

With only 8 panels you'd be under using a 5kWh inverter meaning it's be less efficient.

Not sure why you think that? Assuming the 8 panels are connected to just one MPPT input, the input voltage (Vmp) will be around 300V, so well within the optimum MPPT range for most modern inverters. i.e. that configuration should be just as efficient as having 16 panels in two strings across 2 MPPT inputs.

 

[Everest]

Surely in that case every inverter would be inefficient as they are rarely fed with the full capacity of the panels, and I'd guess they would be hybrid so DC-DC to the batteries?

True, we rarely get maximum power. But MPPT tracking algorithms will adjust current draw to gain maximum input voltage x current in order to gain maximum power. The typical graph for modern PV panels' max power will show voltage ramping up quickly, with the current largely dependent on luminosity. Hence the voltage presented at the inverter for the PV string for any given luminosity (Vmp) will typically be around 80% of Voc and, unless you are running less than 6 panels, will typically be within the ideal MPPT range. Obviously a good system designer will match panel's Voc & Vmp to the ideal range for the specific inverter.

If the OP can post the tech data sheet on the proposed panels as well as the inverter, I'll happily look at the numbers to give my 2p worth

 

[Everest]

The typical graph for modern PV panels' max power will show voltage ramping up quickly, with the current largely dependent on luminosity.

Here's what I mean in graphical form for a Trina Vertex S 440W panel.