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Future proofing vs initial cost for inverter


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Hi guys


Currently I intend to buy an infini solar 3kW plus.

But, I'm wondering if I should consider another alternative like the axpert series and upgrade to the infini later.

The stand where I'm hopefully soon going to be buidling our house is serviced by ESKOM directly.

Currently there is a trend where municipialities are starting to open up their grids for feed in for solar roof top PV.

I know NERSA is busy with regulations regarding this but I wonder if ESKOM itself will allow solar roof top PV feedin.

So this is where the trade off comes in, go the infini route and potentially not be able to feedin or just stick with something bi-directional for now and potentially upgrade later but then the bidirectional second hand value will be a lot less as a lot of guys would want to do the same thing to feedin?

Any suggestions?

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Hi there,

I'd think that if NERSA as the energy regulating authority decides you can feed into the grid than ESKOM has to follow. I could be wrong but new building regulation require a green component for new buildings (like solar heating, not sure what else).

I refer to an article in Mail&Guardian from 15/01/2015, not sure whether this is already outdated:

One can expect a low tarif on electricity sold into the grid, talks are R0.50/kWh. At the same time, an extra tarif is discussed since PV without storage would feed in at the wrong times leading to a steeper demand at peak times in the morning and evening. The drop in supply when the sun goes down would require more power stations to come online at peak times.

To summarize: you might get little pay for feeding in and might pay a higher tarif when using grid electricity. In addition a further network charge for PV feeders is also mentioned.

That sounds now all pretty negative and maybe there was some exageration by the author.

My personal concern would be where to get electricity during loadshedding if my PV system does not have sufficient storage capacity.

The fixed fees for network and maintenance make up about R600 of the monthly electricity bill. I would like to save these costs, too. For a new house, i personally would design for off-grid solar power and solar water heating and gas for cooking.

Have not done the calcs though but a payback time of about 8 years looks ballpark to me (R150,000 investment and R1,500 monthly savings).

I cannot commend on your technical question regarding when to buy what kind of inverter.

C u

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Ok, if you not sure where you going with the solar, I still think the InfiniSolar 3kw unit is best, just for the simple reason that it is programmable.

It can do backup power or grid-tie or both.

Only problem with these units is that you cannot parallel them.

I would love a 5kw unit !!!!

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I have also been comparing the axpert and the infinisolar and one of the main reasons for the later was how the grid tops up the infinisolar and not the axpert. For example, if u get a 3kw solar power and ur power needs are 5kw, my understanding is the axpert will switch to grid for full 5kw whereas the infinisolar will sync and 3kw by solar and 2kw by grid ... can this be confirmed by the experienced guys?

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Hi Hagger

Just went through this myself. You are correct - the infini is "true" hybrid as it can use from any source combined AC(grid) and DC (pv panels/batteries)

The axpert doesn't - it can combine pv and batteries but if the load is above its rating (4000w for the MKS 5K) if will switch to eskom.

In my experience there are other questions that made me go for the axpert rather. It depends on how you plan to install - ie - run the whole house off/via it, or are you going split circuits only (lightS perhaps etc) - reason is the total draw you can run trough the inverter before it trips.

The inifiis smaller - think the max load is 3000w? That's less than say a smeg oven with the grill on (4100w max) - kettles are around 2000w, dishwashers more etc etc... Option one of everything is easier and less electrical - options two is more electrical and bigger seperate DB bord etc - and as your system grows you end up having to re-wire more often.

I went option 1 - so all In - and I'll try manage the simultaneous loads to stay under the 4000w (it does allow "spiking" - but have not tested how much or how long) - if it doesn't work smooth all I need is another axpert in parallel - doubles my load to 8000w - which is more than enough. It also offers 2 other advantages : I always have a backup inverter on hand should something break - and it allows me to add another 3000w of panels for future proof.

My install is probably going live in a week or two - I'll post some details - but you are welcome so email me and I'll give you my number and I'll share my experience and what I've picked up.

[email protected]

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