Is it worth getting ‘Battery Ready’ solar?

Before we get started, any solar system can get batteries added on later. This means the first ever solar system was battery ready. And you don’t need to worry too much about whether your solar will be able to have batteries added later.

But, is it worth taking steps and making choices when getting solar, so it is better placed for a battery in the future?

The key part of the equation is the inverter as part of your solar system. The job of the inverter, amongst other things, is to take in the Direct Current (DC) power generated by your solar panels, and convert it to Alternating Current (AC) that can be used by your home appliances or supplied into our AC electricity grids.

You may realise that batteries we have at home, like AA or those big old ones from Dolphin torches also use DC. So in the future if you get a battery, it will charge up using DC and also discharge supply DC. This means, our battery needs an inverter too. To convert the DC from the battery into usable AC power, and vice versa. Sometimes the inverters you get with a battery are called an AC (battery) charger.

Tesla announced last year that all their Powerwall batteries will come with an inverter included, to make them plug and play (and probably some other benefits Elon has thought up). Many batteries don’t include an inverter, so if you have solar, then get a battery, the solar company will install a new battery and inverter.

With these batteries, this means that when you have excess solar, and that solar electricity is used to charge the battery, it goes like this:

  • DC solar supplied to your solar inverter
  • Converted to AC by the solar inverter
  • Convered back to DC by the battery inverter

This is called ‘AC Coupled’. There are some losses during all this conversion, but not large.

Now, what is ‘battery ready’ solar then?

‘Battery Ready’ typically means your solar comes with a hybrid inverter, that can manage both solar and battery. For example, the Solar Edge ‘Storedge’, as a single inverter, can do:

  • Convert your Solar DC electricity into usable AC for home and grid
  • Supply your solar DC direct to you battery to charge the battery
  • Convert AC power from the grid supply to DC to charge your battery (maybe during off-peak?)
  • Convert the battery DC power to AC for use by your home and grid

This is called ‘DC Coupled’. It sounds pretty neat, but the benefits are fairly limited. It avoids some losses, but these are minor.

Battery Ready costs more and can limit your options.

When we got solar for our house, we got the Solar Edge ‘Storedge’ inverter. This costed $700 extra.

Storedge inverters are a certain voltage (400V), and were designed for 2 of the first batteries coming to market: the Tesla Powerwall 1; and LG Chem HV. Unfortunately, the Tesla PW1 was soon surpassed by the PW2, and Tesla announced they would include their own inverter for all PW2s. Solar Edge were not happy I assume!

For us, we had spent $700 extra, and if we wanted to use the benefits of our hybrid inverter, our only battery option was LG Chem! As I work in energy, I was already aware of this limitation, and knew I was fairly keen on an LG Chem battery if we got one.

For other hybrid inverters, it is a similar situation. There are over 40 battery suppliers in the market, with many times more battery options available. Hybrid inverters are designed for some batteries, but not all. So getting a hybrid inverter now, so your solar is ‘Battery Ready’ can limit your future battery options in the future. One of the reasons we got a battery late last year is I was worried that LG Chem may discontinue their HV batteries, and we would have no hybrid options. It is a rapidly changing market.

That said, as we had a hybrid inverter and ‘Battery Ready’ solar system for an extra $700, we have some benefits:

  • Avoided cost of 2nd inverter – ~$1,000
  • Potentially easier installation and connection
  • Battery and solar monitoring in one place – our Solar Edge monitoring app (this is probably possible with 2 inverters anyway, like with the Tesla battery app)

Conclusion

We are entering a new world of energy. New products and technologies. It is challenging to assess the right strategy and options when investing in solar, and batteries. And things are changing quickly.

Generally, any solar system is battery ready. Getting a hybrid inverter so our solar is ‘Battery Ready’ costs more, may save you a few hundred dollars down the track, but limits your options. If you keen on a Tesla Powerwall in the future, then you don’t need to get a hybrid inverter.

For the reasons above, for the Sunny Shire Bulk Buy 3, we don’t recommend getting a hybrid inverter. This has become clear to me going through the process myself, of getting battery ready solar, then a battery 8 months later.

1 Comment

  1. DC Coupled battery systems can increase the allowed over-sizing of arrays without paying for a larger inverter (upto $700 extra of course)

    Potentially, a hybrid inverter (with DC Coupled battery) can be programmed to only direct trimmed generation into the battery, upto a certain time (maybe 3pm), which maximises the generation of your array.

    Upsizing the inverter is not the same, because export limiting can still “waste” the power.

    In perspective, trimmed power may only be 2-5% of Generation.

    In defense of Hybrid Inverters & HV Battery coupling (vs AC battery coupling):
    1) it is more efficient to charge a 400V battery with 350-600V DC generated by the solar panels than down-scale voltage to 48VDC (or double conversion)
    2) it is much more efficient (and easier) to scale down voltage to 230VAC, versus scale up voltage (from 48VDC) to 230VAC.
    3) It is more efficient (both losses and also wear/tear on electronics) to have minimal voltage adjustment vs triple conversion (inverter, rectifier, inverter).

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