Solar / Battery Storage considerations

Not sure if this equates, but by Solis 4G Inverter quotes the following figures. Dont think I can prove that though.

SolarEdge report a higher inverter output than the net meter. That is where the 95.5% comes from in my case. I’ve averaged the figures. The net meter is probably accurate to 1-2%.

I also found a US government energy site talking about 80% round trip efficiency for lithium batteries in general.


If I remember you don’t have a battery so all solar is converted and used either in the home or by the grid. Conversely home use in excess of Solar available results in drawing from the grid

The SolarEdge app gives me approximate figures for home consumption direct from solar or the battery, and grid import or export. So I can apply different efficiencies but I’m not convinced I am given sufficient information. The crude implication is that battery efficiency may be even lower.

I’m surprised no one with batteries is concerned about the efficiency of batteries. I suppose there is payback nonetheless!


I think a concern will be is whether the inefficiencies are included in calculations given by solar/battery salesman. Certainly when I’ve done calculations, even with current high fuel costs, I cant make batteries viable, with payback not coming until year 11 for a 6KWh battery. That’s assuming 100% efficiency, then you need to consider when they might need replacing, and to me it seems a lot of extra hassle for no big gain. Of course all houses are different

FYI Panel payback looking like just over 6 years, so very pleased with that


It will depend on the tariff you are on. Octopus have several worth looking at if you have a battery (using it for load shifting).

I’m on Flux. Last winter Agile would have been 30% cheaper as on most day there wasn’t enough left to export without having to buy some before the next cheap rate. From May to October I can export 10kWh/day with some import judging the likely solar.

For the last 12 months I have paid £25/month to cover about 4K miles and heat with an ASHP supplemented by a wood burner in the evening. It a 300m2 home so big and fully heated to 18/20c apart from the cold spells.

Not dissatisfied but no one told me the battery round trip would be 80%. In fact the blurb implies 95%.


I pay 7.5p per unit at night and have ( as well as an EV) 19kWh of home batteries. Plenty to run all day in the dark winter months.
My PV export gets me 15p per unit.
Battery storage works for me. I tend to dump the battery each day before the 7.5p rate kicks in too.
My import from the grid is at 7.5p for about 99% of the time.


Last year, once I take into account my FIT payments, my whole electricity bill was a net £220, so it would need a big negative bill to make Batteries work for me. (Remember I do also use a solar diverter for 95% of hot water which covers washing machine, disk washer, and free kettle for various things including weed killer). What I am waiting for is Car to Home/Grid In an EV vehicle - but no rush for that quite yet.

So is a big negative bill happening for people?