A bidirectional solar meter holds two registers — one tallying the units you draw from the grid, another tallying the units you push back towards it — and those two numbers are not symmetrical halves of one story. They carry different prices, they appear as different lines on the bill, and one of them is largely an outcome while the other is a lever. The lever is self-consumption: the share of your solar production that gets used inside the house before either register ever sees it. The registers tell you what already happened. Self-consumption is what decides it.
I stood at the side of the house just after seven one evening, torch in my mouth, working the little blue button on the meter box. It's the ordinary grey thing bolted to the wall near the gate — same housing as every other house on the street, dust in the corners, a spider that has clearly been there longer than I have. Press the button once and the display lights up green. Press it again and it scrolls. Press it again and there's a code, then a long number.
The codes matter more than the numbers the first time you look. One of them is 1.8.0. That's the import register, the one that has been running since the day the house was connected, counting every unit the municipality has sold me. Then there's 2.8.0. On my meter, for a long time, that one sat at zero. Then it didn't.
The meter is an accountant, not a gadget
It helps to stop thinking of the thing as clever. It isn't. It's a bookkeeper at the fence with two notebooks and a rule about which notebook each unit goes into. A unit crossing towards the house goes into notebook one. A unit crossing away from the house goes into notebook two. The meter doesn't know or care whether the unit in notebook two came off your roof, out of your battery, or out of a generator — only which direction it was moving when it crossed the point of supply.
That is what "bidirectional" actually buys you: separate accounting. Not a feature you can feel, not something that makes the lights brighter, just two tallies that can be priced differently. And they usually are priced differently, because the unit you buy from the municipality and the unit you sell to the municipality are not the same product in the tariff's eyes. One is retail supply at your tariff's energy rate. The other is a credit, set by the municipality's own schedule, and it is generally worth less per unit — sometimes a good deal less.
Two lines on the bill, and everything underneath them
When the statement comes, look for the two energy lines first: units imported and units exported. Then look below them. That's where the accounting arrangement really shows up, because a tariff can charge you for the connection itself in ways that have nothing to do with how many units crossed the fence.
Some schedules include a fixed or capacity-based charge that applies because you have an embedded generator on the property. It appears whether or not the export register moved that month, and whether or not you exported a single unit. That is the difference between being credited for export and paying for the privilege of being allowed to export. Both can be true on the same bill. Neither is a technical question — each one is a line in a document the municipality publishes.
You can't read the arrangement off the meter. The meter just counts. The pricing lives in the tariff schedule, and the schedule is the thing worth downloading and reading properly, definitions and all.
The export register is last in the queue
Here's the part that took me a while, mostly because the inverter app makes it look like the panels are pouring electricity into the grid all day.
Behind the meter there's an order of operations. Solar production goes to the house load first. Whatever's left goes to charging the battery. Only after the house is fed and the battery will take no more does anything head for the boundary — and only then does 2.8.0 start moving. The export register is not measuring your production. It's measuring the leftover after everything else has had a turn.
Which means it's quiet most of the time. Early morning, the house imports. Mid-morning, the panels cover the load and start refilling the battery. Around midday, if nothing big is running and the battery is already full, the surplus spills over the fence and 2.8.0 ticks up. Mid-afternoon, the same. Then the sun drops, the battery takes over, and 2.8.0 stops dead. At night it doesn't move at all — the inverter is either asleep or running on stored energy, and every unit the house uses after sunset comes from the battery or through the import register.
So the export register only ever records the surplus of a few hours. Switch the inverter off and it freezes. Let the battery fill and stay full and it runs. Run the geyser at midday and it slows to a crawl. It's a record of what you couldn't use, not a record of what you made.
The number you actually control
This is the whole thing, and it's why I stopped staring at the export figure.
A unit you use inside the house never appears in either register. It just doesn't cross the fence. And because it doesn't cross the fence, it avoids the full retail rate you would otherwise have paid for it — including the block of the tariff you're sitting in, and the levies and taxes attached to that rate. A unit you export earns whatever the schedule credits you for an exported unit, which is structurally less, and in many cases only offsets the energy portion of the bill rather than the whole thing.
Put plainly: one unit kept at home is worth more than one unit sent out. That's a structural statement, not a rate. Check the gap against your own municipal schedule, because its size varies, but the direction holds across most of the tariffs I've read.
Notice what that does to the question of control. You cannot change the export credit. You cannot change the fixed charges. You cannot change how the meter counts or when the municipality reads it. What you can change is how much of your production gets used inside your own house instead of leaving. Geyser timers, pool pump schedules, the dishwasher, the tumble dryer, when the battery's reserve floor is set, whether the inverter is configured to export at all. Those are the levers. The registers are the scoreboard.
The app and the meter will not agree, and the meter wins
I've had mornings where the inverter app proudly reported several units exported, and the meter's 2.8.0 register had moved by a fraction of that. There are ordinary reasons for the gap. The CT clamp that tells the inverter which way current is flowing can be clipped onto the wrong conductor or facing the wrong way. The app can be reporting the inverter's own calculation at the inverter terminals, while the meter measures at the point of supply, with cable losses in between. The meter's export register can be present in the display but not enabled for billing — it's not uncommon for the register to exist physically and only start counting once the SSEG application has been approved and the meter has been reconfigured. And on some prepaid meters, reverse flow isn't counted at all; it's treated as an event, sometimes with a trip and a tamper log rather than a neat tally.
Forget arguing with the app. The billing instrument is the meter, and the authority on what the meter's numbers mean is the municipality's tariff schedule and your SSEG approval conditions. Reconcile once a month: read both registers, write them down, compare against the statement. Do that three months running and you'll know your household's actual pattern better than any estimate anyone could hand you.
When you have to stop estimating
Some things you can work out at the kitchen table. Others you can only confirm from the municipality, and it's worth knowing which is which before you build a spreadsheet.
From the official schedule only: the credit value applied to exported units and whether it's a straight rate or a percentage of a tariff line; whether the credit is applied before or after VAT; whether unused credit carries over to the next billing period and for how long; whether there's a fixed charge tied to embedded generation and how it's calculated; whether export is permitted at all under your tariff, and the maximum export capacity your SSEG approval allows; and how the credit is delivered if you're on a prepaid meter, since a token and an account credit are not the same thing.
On the import side, the block thresholds matter more than most people expect, because a self-consumed unit is worth more when it displaces a unit in a higher block. That's also in the schedule, not in a call-centre summary and not in a blog post — including this one.
For everything else, the method is the same as it's always been. Read 1.8.0 and 2.8.0 on the same day each month. Write both down. Watch the gap between what the house used and what it pulled off the grid. That gap is your self-consumption, and it's the only number in the whole arrangement that you get to move.
