PeterP

Heat-pump is more energy efficient but not necessarily more cost-effective. EV Tubes and PV have zero marginal cost, heat-pumps reduce the marginal cost. If the goal is minimizing running costs then zero marginal cost should win. If ROI is not a concern then a heat-pump wins on it's efficiency

Yes but at what cost? For the amount of money you spend installing the heat pump you can have the PV power (at zero marginal cost and 25 year life) to run the normal geyser element plus plenty excess power for other loads when water is up to temp. Heat pumps are more energy efficient for sure by the factor of 3.5 but I'm assuming he is looking at best option financially and if you factor in extra upfront cost, 10 year life and maintenance then the heat pump for such a small system may lose out. But as I said, it depends - if he doesn't have other loads or battery to push the excess PV power into then it might not work. If he was only heating water then heat pumps might work.

As with most of these questions - it depends. If you have enough excess PV power during the day to run 2x 1.5-2kW element for 2hours then thats your solution. If your load-profile won't allow the geyser load without having to add panels then it will be slightly cheaper to much of a muchness to add EV-tubes as opposed to adding extra PV panels. Heat pumps are typically only viable on bigger systems for water heating + they require maintenance and have shorter lifespans.

Agree with everything Plonkster said except the comment: "It's also cheaper to buy gas for the next few decades than installing a larger solar system" You got gas to come in at around R2/kWh - solar is much less, even with storage. And the solar cost would be fixed whereas gas is likely to go up. Financially gas makes no sense, especially compared to solar.

I believe Kodak is a Segensolar own brand made by Voltronic with some tweaks.

Some CoCT offices have expanded the 25% rule to also include off-grid non-synchronised systems - or so it seems with some of the replies people have been getting from their registration applications (not all, as plenty have been approved). The restriction has merit for SSEG systems but not for non-imbedded systems. In my world Embedded means synchronised with the grid whether set up to export or not. SSEG means the PV system can share the load with the grid, which a non-SSEG off-grid system cannot - the non-SSEG system is either grid or pv/batt - load is never shared. Therefore to call an off-grid/UPS system SSEG is a misnomer and possibly where the 25% rule expansion has crept in. The main implication being that an SSEG system will go down and up with the grid whereas an non-SSEG system will work independently of(f) the grid and therefore will not affect the grid when grid switches back on - in fact it will alleviate the situation when batteries are still carrying system. I'm not sure if this 25% (SSEG) rule expansion to also include off-gridUPS systems is now the rule going forward, or just some of the CoCT offices not being completely aligned with regulations? Installers and customers need clarification on this.

With the Solar MD battery AI settings you overcome some of the limitations of the Axpert inverters as it lets the BMS control the switching based on accurate SOC and it allows user to set the % trigger points. Furthermore they allow for relays to be set for geysers or similar which will trigger when excess PV is available so you will be able use your own preferred settings (SOC vs Load vs PV) to determine trigger. Unless you have very favourable feed-in tariff (which we don't) or only want to off-set a very small % of your Eskom usage the off-grid battery option is improving in price and useability. But ultimately it depends on a cost benefit analysis of the desired functionality as Plonkster says.

Instead of swapping out inverter - Work out how much energy you are losing and add battery capacity to capture the energy - you now have 48V inverter which is compatible with Solar MD Lithium Ion batteries amongst others. It will never make 100% use of PV power unless you match/oversize batteries but it's the better alternative in my opinion as it gives more off-grid resilience and a grid-tie inverter will also spill power unless you have access to feed-in facility.

Locally Solar MD is introducing this solution. It can be set it up on Solar MD's logger V2 if you are running a Solar MD Lithium Ion battery - system can be set to allow geyser to switch on once battery has reached an adjustable pre-set SOC and the PV exceeds load by sufficient watts to run the geyser. I believe you can add two relays and it' works on off-grid systems. I want to run pool pump and EV charging like this. I will be testing this in the near future and will report back.

Found a V2H device which comes in 3kVA and 6kVA. It can only discharge and only works with Nissan Leaf. Cost is R35K and 50K respectively. Compare that to the amount of kWh you get access to in current and future EV's and it may make sense. If one had a 40kWh Nissan Leaf you'd probably have access to about 35kWh and you'd use 5-10kWh for your daily driving leaving a potential 25-30kWh to use as back-up or to carry you through the night at a cost of R1-1.5K/kWh - substantially cheaper than buying equivalent sized Li-ion battery. Charging at work or via home solar system during the day would get you off-grid over night quite nicely. And it would help utilities flatten the duck curve.

Nissan claims Tesla got it all wrong - I'd be tempted to agree although Tesla don't seem to get too much wrong too often...... https://thedriven.io/2019/07/11/nissan-sees-leaf-as-home-energy-source-says-tesla-big-battery-waste-of-resources/

If you include upfront costs then EV's in South Africa lose on TCO calcs - 100% agreed.....but if we start looking at including external costs as well, then the playing field may be a bit more level......

and if you run it off solar then cost is half that....Upfront cost and availability is the only obstacle right now

The cost per km for an EV about R0.35.....a 15km/litre car is over R1.00. And this is before you add in maintenance and depreciation both of which favour EV's. There is room to create parity once upfront cost of EV's is equal to ICE.

Google suggests that 90% of EV charging in the US currently takes place at home overnight - taxing fast charging won't cut it. We currently pay about 1/3 tax on our fuel - that's R6-8K (rough calc) on an average vehicle pa. It's going to be a challenge.

Except you'll find that the primary source of supply to an EV is a domestic wall-plug.....fast charging is only necessary to keep EV's going on longer trips or for top-ups. The funding model will have to be completely re-worked.

The way to solve the fuel-tax issue is to introduce road-pricing - pay for the km's you drive. With this you can also vary pricing road by road to re-direct traffic to better manage congestion.

You can add all the panels you like - the question is whether your inverter will like it....some apparently just throttle once it reaches max capacity, others might melt from what I understand. Some newer Axperts will just throttle at 4kW and you get a nice flat 4kW line the whole day - others have a max for a reason.

CoCT limits the size of inverter (on grid-tied systems only) which in turn limits the possible amount panels as most inverters can only take a factor of 1.2-1.5x the size of inverter. So indirectly CoCt is limiting the number of panels on grid tied systems

15kWh/day per geyser is quite a lot - how many people are showering and how far away from showers are the geysers located? And are your hot-water pipes insulated? As with everything heating/cooling/powering - start with the low hanging fruits: Reduce consumption (shorter showers), insulate everything to reduce heat-loss (incl. shortening route as much as possible), use timers to have heating occur as close to usage as possible - then you'll know how to size your system. On face value EV tubes and or heatpump sounds like the way to go. Then add PV later to pick up powering heat-pump or elements later.

Plonkster is pretty close - the retail price for Solar MD 3.7kWh battery (complete - no extra cables, enclosures etc needed) is R28,800 excl VAT. Add R3,500 for the logger if monitoring is required. Battery is compatible with any 48v battery charger/inverter and logger can be used with an increasing number of inverters - Axpert, SMA, MLT, Victron, Microcare, Studer, Sungrow, and Imeon. Most retailers sell systems and then the pricing gets a bit more fluid depending on total system sizing. The package is impressive and very installer friendly + the guys are constantly tweaking and improving software in logger and BMS + making logger compatible with more inverters.

1. The 3.5kVA limit is there to ensure all grid-tied SSEG customers remain net-consumers (import more than they export) + to limit excessive feed-back. The UPS/Off-grid generator cannot export hence this does not apply. 2. I don't see what patterns they create that are any different to flicking a switch on any appliance - home-automation could create the same patterns. The grid merely picks up what ever load that was being serviced by generator - none more, none less and entirely identical to what would have been serviced by grid prior to generator installation. 3. Correct - the grid-tie system is synchronised and load is shared between grid and generator, whereas the generator picks up the load in its entirety. 4. No problems that wouldn't have been there prior to generator being installed as loads remain the same whether serviced by grid or generator. In lieu of above I don't see any need for limits on off-grid/UPS systems as they are not adding any stress that wasn't already there. It's akin to saying you are only allowed to use 15.75A of your 63A Eskom supply - if that's the case then what are the 63A breakers for?

Plonkster I don't agree - the UPS/off-grid system will fall back to grid when battery capacity is too low - it's highly unlikely that all such installed systems will run out of battery at exactly the same time. The television tea episode would be more of an impact and if they didn't find a way of legislating away the tea-break then I don't see the need here.

might as well make a "No coffee until after 9am" - rule.......An off-grid system can only put less stress on the grid, to say otherwise is non-sensical. Any load carried by the off-grid system would, in it's absence, have to be carried by the grid and saying the demand is more sudden when switching over is problematic means switching on/off your mains at DB board is equally problematic.

If the "sudden demand" narrative catches on then there will be a ban on geysers and underfloor heating following shortly. Never heard of a "25% of supply max demand limit" and council has already set a precedent with numerous off-grid systems identical to the above having been approved so I think someone just had a bad day...