What is a solar smart meter? Do I need one?

There are also lots of devices called smart meters...

#1 The Smart Meter that is owned by the electricity retailer

The original electricity meter was elegant, but dumb, a bakelite box with a disc that spun around behind a little pane of glass to count kilowatt hours. (watching solar turn them backwards never gets old).

A dumb analogue meter

Many of these dumb analogue meters have been replaced with dumb digital meters. They are still dumb because they:

• cannot communicate with your retailer (they need a meter reader to physically go to your home)
• cannot be used with time-of-use tariffs (ToU). They record - at best - an off-peak rate and an on-peak rate, whereas a ToU tariff needs a meter that can handle peak, shoulder, off-peak and super-off-peak time intervals..

A dumb digital meter

When you install solar, if you don't already have one, you'll get a digital "smart meter" installed and owned by your electricity retailer, and it provides the interval data that is used to generate your retail bill whether it is a ToU or Standard tariff. They're internet connected via the 4G network, remotely read and remotely operated for controlled load, typically off-peak hot water or floor heating.

If you would like you can access the readings from this retail meter yourself, with either a retailer phone app or by following the procedure listed here to get the raw information. It's your data and you're entitled to it.

A digital smart meter

#2 The smart meter that is owned by the homeowner

The other "smart meter" is a customer-owned device, fitted in your switchboard, which measures energy coming and going from the grid. It is a consumption meter that allows your solar inverter to see what is going on in terms of generation, self-consumption and export, and it's often a legal requirement, used to protect the grid by limiting the peak export capacity of your solar system. 

It also means you have valuable information available via a monitoring app so that you, the owner, can see how much energy is flowing where. This is a real boon because it means you can observe in almost real-time how power is used and how behaviour change improves things. It can show if there are faults that need attending to and even better, a consumption meter will prove if you have the surplus energy required and the consumption patterns to make buying a battery worthwhile. 

Fronius smart meters, single-phase and three-phase versions.

There are also stand-alone "smart meters" like Solar Analytics or Wattwatchers, which don't talk to a solar inverter, but usually just let you know what's going on. They can tease out individual loads like air conditioning and pool pumps and allow you to compare to other solar systems in the area and compare other retailers using your own data. Just to make it confusing Solar Analytics can also be integrated into some inverters. To get the best functionality, you will still need an external consumption meter wired to the inverter.

Two 3-phase Solar Analytics meters

And then there are "smart meters" like the CatchPower relay, which might also talk to some solar systems as a consumption meter. It has its own monitoring app and is aimed mainly at switching things like hot water or a pool pump on and off. Basically, when there is excess solar energy, you can divert it to doing something useful instead of exporting it to the grid.

And with that in mind, a consumption meter or at the very least, a measuring coil is required if you have a battery or hybrid system. It allows the hardware you have installed to measure energy flows and make decisions to best prioritise whatever is available, be it solar from your roof, cheap midday energy from the grid or stored energy you've already collected.