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.

 

[Bam Bam]

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

I'd generally say 10kWh would be a good idea rather than 5kwh.

I think batteries will become more valuable as more renewables get added to the electricity system. Electricity was negative 10p the other weekend when it was both sunny and windy. You get paid to take it!

Have you got a quote from heatable as well? They seem to offer some 0% APR which I don't think Octopus do any more.

 

[T1 Terry]

Right guys got some figures to digest and some questions ,
5kw battery or 10kw battery , which would you recommend
View attachment 45202View attachment 45203View attachment 45204View attachment 45205

Just like solar, you can't have too much battery. Don't worry about export to the grid limits, inverter capacity to power the house from the battery and think about adding the EV battery into the equation by using a V2X type of system that works on the DC side direct from the solar to the EV battery in each direction.
Over on the Aussie thread, @wattmatters does a video series with another member Neerav Bhatt MG4 in Australia | MG4 EV (2022 to 2025) Forum regarding this use of the MG EV battery as part of the whole system ..... worth at least thinking about

T1 Terry

 

[wattmatters]

Over here maximum inverterwe can fit is 3.68 kWh, we have 12 panels fitted

Is that a regulatory limit of some kind, or just a small roof? Relatively small power panels being a bit over 300 W. Modern panels are more like 500 W each.

The calculus for how much solar and battery to get requires an assessment of a whole range of factors as well as an understanding of what you are seeking to achieve.

But as a start it helps to have done an energy audit as well as anticipate what changes in household consumption can be reasonably expected.

The it's a matter of what can physically be installed, local code and network/grid requirements, and the nature of tariffs applicable in your area.

 

[Giller]

It’s regulatory, maximum you can have in NI.

 

[decrep]

It’s regulatory, maximum you can have in NI.

that sucks.
But more panels and bigger battery won't hurt. especially when you have lots of cloudy days

 

[T1 Terry]

I think all inverters these days have an adjustable upper export limit, the reast can be used in the house from both the solar available and drawn back out of the battery/s as required, then replace by solar or cheaper o/night power ......

Over this way, that cheap overnight power will soon be a thing of the past. Once the last of the spinning mass frequency and voltage stabilisers as shut down, the newer, faster to react, battery backed, frequency and voltage forming inverters will completely take over.

Coal fired stations are being shut down because they are well past their service life after they were bought up by interests who were looking for quick returns and didn't maintain the infrastructure with longevity in mind, fix it if and when it broke worked well for a while, with next to no maintenance shut down periods, those breakdowns are getting far more frequent.

For some reason, only known to those that made the decision, South Australia has a gas fired power station that runs 24/7 .... why, in a state that sells excess renewable energy to the other states via the interconnector, so we have periods during the day that we can be paid to take power from the grid to store it .....

T1 Terry

 

[decrep]

Yes W.A. has a 5kW limit on system without batteries, but with battery, the panels can go up to 10kW, so in theory we can export 5kW, and charge battery at 5kW at the same time.