G8 or KH8 inverter for solar only system? and what size for 16 panels?

[werdas]

hello

Im getting quotes for solar system 16 panels , no battery ( as numbers doe snot add up for battery to be paying off in 10 years)

I wanted to go for kh8 inverter in case I decide to add battery in the future

one quoter said that I will be getting error on the app, and at the time of getting battery that battery might not be compatable with kh8,
so they are pushing me to have g8 one

the other quoter suggested to have solis inverter, not sure .... if they are any good

also another Q is kw of inverter , Im getting quoytes for 8kw, 7kw, 6kw inverters,
which is the right size?

many thanks

[Dave Foster]

Yes go with the KH8 inverter and if possible start with just the minimum size of battery - if not possible you can always add them later, there are plenty of Fox units that are and always will be compatible with the KH inverter it is one of their flag ship domestic products.

In terms of sizing get the largest you can, 16 high output panels would be close to the 8kw output and having capacity to add more later is a real benefit. Also the larger inverter when fitted with batteries can provide a higher power output to cover your bigger house loads.

Solis are also good inverters but I believe Fox have the better range of hybrid battery solutions.

[WyndStryke]

... no battery ( as numbers doe snot add up for battery to be paying off in 10 years)

...

Consider this approach -

• Charge up overnight on the E-on Next Drive tariff, 6.7p/kWh 00:00 - 07:00 to 100%
• Run off that during the day (to do this, you need batteries at least big enough to run for a winter's day where there is little solar generation)
• Export any solar generation at 16.5p/kWh
• Export surplus battery in the afternoon and evening, at 16.5p/kWh, so that you are left with just enough to get to midnight

That should pay back reasonably quickly if you have enough wall space (preferably in a garage or similar) for EP11 batteries (which have a good price per kWh). Energy Cube batteries cost more, so the payback period is longer, but even those will pay back reasonably quickly.

There are also other tariffs from other suppliers where you can do similar things.

16 panels

Get all the panels you can fit on the roof, for the west/south/east. North can also be worthwhile as long as the pitch on your roof is gentle. Additional panels are relatively cheap, because a lot of the cost of an installation is overheads.

[werdas]

thanks,

ok, so lets say I buy 1kw for 7p and export for 15p
so that is 8p profit per kw
if my battery is 10kw, I leave 1 kw in reserve
I sell export 9kw in the morning=9x8=£0.72
times 365=£262.8 per year
battery cost £3000/262.8=11.4 year for the battery to pay off
and that is you do this every night for 11 years, but it wont happen as you will need to charge EV, plus energy prices might fluctuate

so it still does not seem worth it
as by then I would need to replace battery


or should I count as not exporting that 9kw and using it?
9kw is 1/3 of what I need per day, but
lets say peak time is 26p-7p=19p per kw cheaper x 9 =£1.71
x 365=£624.15
£3000/624.15=4.8 years for the battery to pay off

[WyndStryke]

but it wont happen as you will need to charge EV, plus energy prices might fluctuate

Strongly recommend that you don't try to charge the EV from the battery. An EV's battery is much larger than a household battery, so it'll just be drained immediately. Best to charge it overnight, simultaneously to charging the home battery.

9kw is 1/3 of what I need per day, but ...

Ideally the battery should be big enough to supply your own needs for a day, the export at the end of the day is only for the surplus that you didn't already use yourself. Self-consumption is the first priority, the arbitrage export is the little bonus at the end of the day for what you didn't already use.

[reef]

thanks,

ok, so lets say I buy 1kw for 7p and export for 15p
so that is 8p profit per kw
if my battery is 10kw, I leave 1 kw in reserve
I sell export 9kw in the morning=9x8=£0.72
times 365=£262.8 per year
battery cost £3000/262.8=11.4 year for the battery to pay off
and that is you do this every night for 11 years, but it wont happen as you will need to charge EV, plus energy prices might fluctuate

so it still does not seem worth it
as by then I would need to replace battery


or should I count as not exporting that 9kw and using it?
9kw is 1/3 of what I need per day, but
lets say peak time is 26p-7p=19p per kw cheaper x 9 =£1.71
x 365=£624.15
£3000/624.15=4.8 years for the battery to pay off

Yes, essentially the battery is saving you from importing at the peak rate (I.e 24p / kWh) so the payback is quicker.

Say you have a 15kWh battery and charge it at 7p/kWh - that's £1.05 to charge. Not taking into account solar, if your usage is 12kWh per day, you've saved £2.04 as you've not drawn those 12kWh from the grid at 24p for example. You can then export the remaining 3kWh at 15p/kWh for a further 45p. Any solar generation means more battery left to export at the end of the day if you choose, so more savings. On 10kWh of generation you've essentially got another £1.50 from exporting (some from solar, some remaining battery).

Obviously payback varies depending on when you use those units in the day, but it's much quicker.