Upgrading inverter and adding a battery

Hi all,

Been running solar 4.4kwh and 9.5kwh battery with a 3.6kwh gen 1 inverter since May 23.

I'm generally happy with everything even though my roof is not perfectly positioned, so I do lose out on optimum sun position.

What I'm finding is that the 2.6kwh restrictions on the inverter means that even with a full battery, I still draw from the grid (such as running a couple of things such as induction hob and washing machine etc), so would a higher rated inverter such as 5kwh help here?

I'm also thinking that an extra battery would also help, married to a bigger inverter, so that I can export to grid for more income quicker and import more when at really cheap or negative rates.

I'm currently with Octopus, fixed export at 15p/kwh and Agile for import. (Example charged last night 8kw at an average of 9p/kWh).

What are people's thoughts about the above?

Also should I consider gen 2 or 3 inverter and what kind of costs are we looking at? (Inverter and additional 9.kwh battery)

Finally, I presume that I have to go through my original supplier for warranty and set-up purposes?

Cheers
Ieuan

I have the 5 kW hybrid Gen2 inverter paired with a 9.5 kWh battery, and that is limited to 3.6 kW peak from the battery compared with the 2.6 kW via your Gen1 inverter. It is only capable of 5 kW when there is also sufficient solar generation.

You would have a large expense with very little financial gain by swapping out your inverter for the relatively short periods when you have combined loads greater than 2.6 kW.

Even SWMBO has got in the habit of running power hungry appliances in sequence such as the kettle (3 kW), microwave (1.4 kW) and washing machine in the heating cycle (2 kW). There are kettles available with a 2kW element instead of the usual 3 kW.

How much peak rate consumption are you actually recording on your Agile tariff, other than when the battery is depleted before getting to a cheap period?

Iguana I think even a 5kW gen-1 inverter would be limited to 2.6kW from the battery. A gen-2 could take 3.6kW from battery.

Can you run washing machine from grid when agile is cheapest, overnight if necessary? You only have to get under 15p/kWh, really, since exporting solar instead of running machine from it earns you that. (ie you should cost your solar at 15p when calculating best way to cover your consumption.)

(We use a travel kettle at home - takes longer to boil, but gives enough for 2 - my OH hasn't mastered running sequentially)

We have 6.4kw panels, 9.5 and 5 kw gen 1 since April 23. We have used 260kw at peak and about 6000 total (EV uses 2400). Not yet a year but I think it will be about total cost zero for electricity - including the car, saving sessions and export. We use the hungry appliances at night on the Intelligent Go rate unless the sun is shining in which case it doesn’t really matter. Charge the battery to 100% at night. The kettle is an irrelevance unless you drink a massive amount of tea! Trick is one thing at a time if possible but don’t lose any sleep over it.
We thought we were getting a gen 2 inverter right up till it was fitted and were pretty annoyed at the time but to be honest it hasn’t been a big problem and probably not worth swapping for another £1-1500 + fitting.

SimonClarke We use the hungry appliances at night on the Intelligent Go rate unless the sun is shining in which case it doesn’t really matter.

Hmm... my take is that running overnight costs 7.5p/kWh, whereas consuming solar costs 15p (opportunity cost).

DD I agree it just feels better! And sometimes more convenient. Small amounts of money involved but I guess it adds up if you’re really worried.

SimonClarke Yeah... know what you mean : I had to charge car from solar on Friday since overnight charge failed for some reason. Much better driving experience on home-grown power :-)

Iguana an additional 9.5kW battery will cost you about £4,000-ish fitted. The inverter another £1,000-1,500

I doubt that either will pay for themselves in the extra charge rate and storage capacity. I did modelling of different scenarios for an extra 9.5kW battery and came up with payback periods of 5-22 years !

Taking yesterday as an example, import rates were super-low at 6-10p for most of the day so it was worthwhile charging and then discharging at 15p. My consumption for yesterday was -£2.50. That was an exceptionally cheap day as it was sunny and windy, but even at that saving it’d be something like 10 years to payback the £4k battery cost.

If you’ve got a 9.5 battery you should be able to avoid the worst of the peak agile import rates, as others have said, defer high load like the washing machine until the cheaper periods.

Yesterday’s cost was about 90p including the standing charge and charging the car so an expensive one! Mind you today won’t be great - no sun whatsoever and cooking a special large family meal so no export but we won’t run out either.

Thanks all, very good points and had made me think that it's not worth it.

Yesterday for me cost £1.22 in imports, but £1.40 in exports, but that was with washing machine and tumble dryer on for at least 3 hrs.

I think I'll stay as in then.

As for small ones, for me even a small net+ is worth it 👍

Probably best of waiting for the EMS before making a decision.
I am told that this is under going testing at employees properties currently so perhaps it will finally arrive this year.
You can then add an additional inverter & battery should you wish.

dragon2905 I'd agree a multi-inverter setup is better, much better charge/discharge throughput rates.

Just as long as the two inverters play well together (which my two gen 1 hybrids do).

Of course the cost of the mythical EMS remains to be seen. Given that it seems to be acting as an intelligent 'head' over the top of the inverters I suspect it (a) won't be cheap and (b) will have its own firmware 'journey' ...

But we shall see