We try to manage our general consumption with electricity production. We don't have an EV, but from March to October, we try and mop up as much excess solar production as we can. We do the laundry (and drying if required) on days that we know will be sunny. Same thing applies to all electricity intensive tasks like ironing, using the hub to make home-brewed beer, using the dishwasher, etc. This has worked well for us in the past, but it does require a lifestyle flexibility to be able to not do these tasks when its cloudy and to be patient to wait for prolonged sunny spells that maximise solar production. Our hot water is also switched off during the day on those sunny days and it's reheated using our iBoost.

Our numbers for April so far have been provided below. So far, we've consumed 597.05 kWh and generated 585.8 kWh. Obviously, we're still consuming at night so we've self consumed 268.2 kWh, but from a carbon neutrality perspective, we imported more or less what we've exported so happy with that. 

If we had a battery, however, we'd be in a solid situation because on a full charge (say 15kW) we'd get through the night and not have to import at all. Comes to RoI which we're still teetering on.

Ah, yes I see what you mean - I'm just getting used to these graphs and the terminology. Does the SolarEdge give graphs that show an average over 24 hours - I mean showing a typical daily usage pattern ? 

Another question ! Would I be able to have the PV power linked straight into my heat pump's immersion with some clever wiring and a switch ?

Posted by: @heat-pump-newbie

Another question ! Would I be able to have the PV power linked straight into my heat pump's immersion with some clever wiring and a switch ?

We use the iBoost to do that but there are many different products on the market. Instead of sending excess production to the grid, it diverts that power to the immersion. 

https://www.marlec.co.uk/product/solar-iboost/

Posted by: @heat-pump-newbie

Ah, yes I see what you mean - I'm just getting used to these graphs and the terminology. Does the SolarEdge give graphs that show an average over 24 hours - I mean showing a typical daily usage pattern ? 

Yes, it does. It also give you an hourly breakdown which is very helpful. This is for yesterday.

@editor That's great, thanks. So the iBoost can just be wired in to the system, does it interfere with the heat pump controls? Mine is a Daikin Altherma 3, it only uses the immersion for the legionella cycle or if I request a boost to the DHW (which is v rare!)

@heat-pump-newbie, the iBoost doesn't interfere with anything and it runs independently of everything. You get a control box that goes in the room where the HW tank is and that wires into the immersion. You then get a separate "unit" that clamps onto your mains cable leading into your consumer box. This unit checks which way the electricity is "flowing" so if you're importing energy, it does nothing. If you're exporting it checks in with the unit near the HW cylinder – if the hot water is below its target temperature (not what's set by your heat pump, but what's set by the dial on your immersion) it'll divert electricity to the immersion and heat water. So your heat pump can be off, and it'll still heat water. That's what we've been doing for a few weeks. The heating goes off in the morning, we have our showers and the water is reheated via the iBoost.

@editor sounds perfect !

@julianc do you have one of these ? you have a similar Daikin to mine. Or is that what your Solec 200 is?

@heat-pump-newbie I chose the Solic 200 over the iBoost as it comes with a 10 year warranty, is built In Britain like a battleship. It doesn’t provide any data. Just fit and forget. An alternative now is the Harvi from myenergi which integrates with the Zappi via the Hub. 
I switch off the legionella cycle on my Daikin as the Solic via immersion heater get the water to 80C (I need to step this down to 65C) in my Mixergy. I set the ASHP to top up overnight. But it doesn’t need to in the sunny summer 

@julianc Ah - so by switching off the legionella the heat pump doesn't need to communicate with the immersion ?  This is in the iboost faq: "The immersions must have thermostat controls but no electronic controls between the Solar iBoost+ and the immersion. Take care not to connect any devices with any electronic controls as these and the Solar iBoost+ will be damaged."

Maybe the controller should be set to not see the immersion at all ?

@hydros is this how your heat pump is set up - I remember seeing that you have one of these too?

@heat-pump-newbie Correct. I have the simple but well built Solic200. Principle is exactly the same as the other devices like the iBoost but a bit older and doesn’t have the monitoring functionality. I’ve had mine for about 7 years now (pre-heat pump era). 

The ideal situation for integrating with a heat pump setup is via a tank with two immersion ports. One for the heat pump, one for the PV diverter. My installers wouldn’t provide this (I am part of a trial with OVO and the installers were rubbish). Instead we have a timed relay switch that isolates the heat pump control of the immersion between 9am and 5pm. The reason for this is if the Solic (or other brand) is diverting electricity to the immersion and then the heat pump tries to do the same you get a 🤯 and the RCDs will trip. Some of the later heat pumps and PV diverters do have more integrated wiring panels to facilitate this operation more cleanly but not all. 

In reality with the Solar PV my water is above 65 most days by mid-morning, even cloudy days like today, so I never need the heat pump to operate the immersion except for the odd day in the depths of winter when the heat pump needs some assistance, this is where my timed solution isn’t great and I’d prefer a tank like the Mixergy. But at £2000 for a tank I can’t justify the change (yet).

A battery connected to my PV, and topped up from the Grid, to run the heat pump (and a few other appliances) is my preferred solution. Much more efficient use of energy than an immersion running at a COP of 1.0