Apollo Gem Compact (Wireless)

2-3 Day
4.43 out of 5 based on 7 customer ratings
(8 customer reviews)



The Apollo Gem Compact is our most cost effective solar PV directors. The unit calculates when the home is producing a surplus of electricity (i.e the solar PV panels are producing more electricity than is being used in the house) and redirects this surplus to the immersion heater on the hot water tank to provide you with free hot water.

This Wireless compact solar PV diverter is a cheap way to maximise you solar PV financial return. The unit is designed and manufactured in the UK and comes with a market leading 5 year warranty!

Apollo Gem Compact (Wireless)

When your solar PV panels are producing more electricity than is being consumed in the home, this little piece of kit diverts the surplus to the immersion heater on your hot water tank. The unit kicks in when there is a surplus of just 70W, making it one of the most reactive solar diverter units available on the market today!

Why Divert the extra electricity to the Immersion unit on your hot water tank?

In homes with solar PV electricity you get paid for any electricity you produce through a Government backed scheme known as the Feed-in tariff. This is regardless of whether you use the electricity in the home or export it back to the grid.

The great value Solar PV diverter

You also get paid to export electricity back to the grid via the same scheme – so why would you install a Apollo Gem Compact and stop exporting electricity to the grid?

The reason is that while any house with solar PV on the roof will have a generation meter installed to record the amount of electricity produced (for the feed-in tariff payments), very rarely will an export meter be installed – instead the exported electricity will be ‘estimated’ by halving the amount of kWh generated. i.e. you get paid as if you are exporting 50% of whatever your generation meter reading is.

Therefore there is actually no point exporting any electricity back to the grid – since you are getting paid anyway, therefore the Apollo Gem Compact diverts any surplus electricity to the hot water tank to ensure none is exported.

Why use a Solar PV diverter?

By diverting any surplus electricity to the immersion unit on the hot water tank, it means that the gas boiler doesn’t need to fire up as much to heat the hot water, thus saving you money on your heating bill. Unlike a TV for example, which is either on or off, a immersion heater can be fed any amount of electricity and it will still function, obviously the more electricity going through the electric immersion unit, the quicker the hot water tank warms but any surplus electricity will heat the water up a bit.

Features of the Apollo Gem Compact

The Apollo Gem Compact is packed with amazing features!

    • Small Compact Unit – 145mm x 115mm x 50mm (height x width x depth)
    • Power saving starts from just 70w PV surplus
    • An Informative LED panel shows the household import / export level and the heater power level
    • Incredibly reactive response time for accurate control under constantly changing generation and load conditions
    • Power sensor extends to 100m (wireless)
    • The Apollo Gem Compact is a solid state design offering high reliability
    • The Apollo Gem Compact comes with a market leading 5 year warranty!
    • It is designed and manufactured here in the UK
    • 1 hour or 2 hour Boost button


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Reviews (7)

  1. Rated 5 out of 5

    Jan Pringle

    A splendid piece of kit. Easy to install; no set-up, just turn it on. Does exactly what it claims to do. I investigated (and rejected) the idea of using batteries to store energy that I would otherwise export to the grid because the pay-back would be too long…

  2. Rated 4 out of 5


    Easy to install and should reduce the cost of heating our hot water over the coming years. Indication System clearly indicates different modes.

  3. Rated 5 out of 5


    Does the job I suppose. That or expensive voltage optimizers they are now trying to sell me

  4. Rated 4 out of 5

    Silent Assasin

    The Apollo Gem is a great little purchase. It means we no longer export electricity back to the grid, everything we make we use. Since the export tariff is so low, it is a bit of a no brainer. Very much a plug in and forget technology!

  5. Rated 4 out of 5

    Chris T

    Free delivery on Mondays to Fridays only is ok but please state this on your ts and cs. Other than that cant fault the product works pretty well so far. No explosions so far haha

  6. Alan

    If the Apollo Gem kicks in at 70 w surplus PV output this would not be enough to power the immersion heater, these heaters consume at least 3000 watts therefore the extra 2930 watts will be dragged from the grid and electricity bills would be very large.
    Excess grid power should be fed to the grid until sufficient power is available to operate the appliances, 70 watts will not do it.


    • James Alcock

      Hi Alan,
      Thanks for your comment – this is incorrect though. An immersion unit can operate at variable energy input, so the immersion unit itself will get hot regardless of how much electricity is fed through it. Obviously there is a vast difference if 70w goes through a 3kW immersion compared to 3000w, but it will still make a difference.

      The important thing to remember though is that zero electricity is being pulled from the grid. The Apollo Gem has a clamp which is directional it can only power the 3kw element when export energy exists. It cannot pull from the grid unless you press the boost button. ( same as all makes pv diverter )

      I hope that clarifies this!

  7. Rated 4 out of 5


    I did loads of research on the internet before investing in a solar PV optimiser / solar PV diverter. There are lots of different brands out there and they all do a similiar thing, but basically the theory is they divert any excess electricity to your immersion heater meaning nothing is exported. Good news cause not mny people have export meters installed, so you are getting paid as if you export 50% regardless of how much you export.

    THe Apollo Gem was the cheapest out there and to be honest it does what it says on the tin. It diverts the excess. Don’t expect to be given fancy charts that are sent to an ipad though, this system keeps it all very simply and just gets on with its job in the background.

    A couple of other plus points, it is wireless and it is really easy to use (once set up) and also it comes with a 5 year warranty to provide a bit of peice of mind!!

    Only downside is that it was not that simple to set up, so needed to call for some assistance, hence my 4 stars!

    if you are looking for a cost effective solar PV diverter, look no further though!

  8. Rated 5 out of 5

    Douglas Maxwell

    The PV installer who installed my Solar PV installed a PV immersion switch with batteries in the transmitter which i didn’t know when he installed it. Ive had it removed and installed the Apollo Gem C wireless.
    its a fabulous bit of kit for the money. A genuine mains powered transmitter (NOT BATTERIES ) like other brands and 5 years warranty. When a manufacturer is prepared to stand by their products for this amount a time you have to ask yourselve is it really good value to fit anything with a warranty of only a few years at best. My advice don’t hesitate. Why bother with more expensive pv immersion devices when this is the best value device of its type hands down.
    Really straight forward to use too. Amazing value great product..