Menu

Monitoring of solar PV system with Tesla Powerwall, immersion heater controller and electric vehicle charging

When solar PV systems first started to become popular in the UK, the majority of installations consisted simply of some solar panels and an inverter. Nowadays there are some excellent products available to help the user get the most out of their investment. Examples include monitoring systems, automatic switching of electrical appliances and, more recently, storage of excess generated electricity. Below is an example of an installation that incorporates all of these. The house has an Economy 7 electricity supply, meaning that electricity purchased between midnight and 7 a.m. is roughly half the price of the rest of the day.

Tip: This is live data! If you hover over the graph, you can zoom in or out, or scroll back in time so that you can see historic data.

Solar PV generation, Tesla Powerwall battery storage and automatic switching of electrical loads

Battery meter

Yellow: This represents the electricity being generated by the solar panels. Yields during the summer are much higher than in the winter.
Orange: This is electricity being used to charge the battery. Any surplus solar electricity will be diverted here. Between November and February when there is little surplus, the battery will charge overnight on cheap rate electricity that can then be used during the day. The state of charge of the battery is represented as a purple line.
Blue: During the summer the battery will often be fully charged by midday. Any excess electricity will then be taken up by the iBoost immersion heater controller for free hot water.
Red: This is the electric car being charged, which doesn’t happen every day. During the summer, the car will charge from surplus solar electricity. At other times charging usually happens overnight on cheap rate electricity, or in emergencies it can be charged at any time. This is achieved using a custom designed and built electric vehicle charger.

Footnotes: The monitoring is achieved using various electronic modules from the excellent open-source OpenEnergyMonitor project. The electric car charger is a custom built unit based on modules from the OEM project. As of May 2017 the car charger is an OpenEVSE unit. This page is a work in progress so things will be added or removed as time goes on, or it may just occasionally not work properly every now and then as I experiment with it.