Monitoring heat pump, solar p/b and home energy


I want to start monitoring the electricity used in our house. I have 4kw solar with a Trannergy inverter. A hitachi yutaki monoblock, quite sophisticated with underfloor heating throughout, zoned into rooms with room thermostats. A solar iboost + to divert spare solar output into a 300 litre tank.

The heat pump does heating + domestic hot water.

I can use a pulse device on my solar meter, not so sure about the heat pump meter, want to monitor heat pump to level 2, really don’t want to add a flow meter to the heat pump as that would be disruptive.

Ideally I’d like this all to be Wi-Fi, I’m quite handy and could install modbus blocks if that would be better.

I just need some validation on what all to buy … single phase house.

Any help appreciated


Hello John and welcome to the forum!

How are the different measurement points spaced appart in your house?

Can you do all of the electricity monitoring at the consumer unit location? how far is that from your heat pump flow and return primaries and hot water tank?

Hi Trystan, thanks for taking the time.

I have two consumer units, one in the garage at the heat pump and solar, I think I could connect up all of the heating and solar with no more than 12 feet of cables, all the heat pump cables, hot tank and flow pipes are in easy reach. That CU has a 100 Amp feed from the house.

The main house CU is in a room approx 35 feet further away in the house, electric comes in there, external electric cupboard on the outside wall.

The main reason for wanting to do this is the heat pump has been a trial to understand, I think I’ve tamed it by watching heat geek and following some advice on flow temps but I would like to monitor the pump and its additional heating element/buffer tank.

I was thinking that the modbus meter units would replace the respective circuit breakers but after doing some more reading I don’t think thats how they are used. My solar has a generation meter with pulsing red led. The HP has a meter attached but its just an LCD display, can’t see any light pulses coming from it, I could replace that meter with a pulsing one if that helps. The HP buffer tank has an electric element embedded which might be up to 3Kw, not sure. I would like to add the buffer heater into the monitoring regime.

Wifi reaches into the garage, no probs there.

Thanks in advance


Hello John

As ever lots of different ways you could do this.

  1. An emonTx4 to monitor the different circuits, you may need to extend the CT cables if you thinking you can monitor everything off a single emonTx4 with 6 CT inputs. You could also use the emonTx4 for temperature monitoring using DS18B20 temperature sensors.

  2. You could monitor the pulse’s on the existing meters. The firmware for the emonTx4 is limited to a single pulse input at the moment even though the hardware could support more. It is possible to do pulse counting directly from a digital pin on a raspberry pi which might be another option to monitor multiple pulse output meters.

  3. Replace the pulse output meters with Modbus SDM120 meters and read the full data output from these via a Modbus reader connected to an emonBase ( raspberrypi).

  4. Does the Trannergy inverter have a data output option? You may also be able to get data from the heat pump with a modbus add on.

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