The energy flows show how electricity moves through your system: from the solar system, the battery and the grid to the consumers – and back into the grid.
Only electricity flows are shown. Heat, gas or oil do not appear, but the electricity a heat pump or an electric heater needs does.
autarc calculates the energy flows for every time step of the year – hourly or at the selected Simulation resolution. Their sum gives the self-consumption rate, the autarky level, costs and savings.
The components
Producers:
Solar system: the hourly solar yield from the linked solar planning. More in How is the PV yield calculated?
Custom producers: e.g. a wind turbine or generator with its own load profile. Their electricity is used, stored or fed in just like solar power.
Consumers:
HouseholdHeating system(e.g. heat pump)Wallbox / EVAir conditioningCustom consumers
Energy flows:
Direct self-consumption: solar power used in the same time step it is produced.Battery consumption: electricity used from the battery.Energy Feed-in: solar power that is neither used nor stored and flows into the grid.Grid consumption: electricity drawn from the grid. With time-of-use tariffs it is split by tariff band, e.g.Grid consumption peakandGrid consumption off-peak.Energy losses: losses when charging and discharging the battery.
How each time step is calculated
In every time step, this order applies:
Direct self-consumption: solar power first covers the simultaneous consumption. If it isn't enough for all consumers, it is shared among them in proportion to their demand.
Charge the battery: a surplus charges the battery – limited by free capacity and charging power.
Feed-in: whatever is left is fed into the grid.
Discharge the battery: if solar power isn't enough, the battery discharges – limited by discharging power and the stored energy.
Grid consumption: the grid supplies the remaining demand.
The battery's state of charge carries over from one time step to the next. Electricity stored at midday is therefore available in the evening and at night – just as in real operation.
The battery in detail
How the battery charges and discharges depends on the product data of the battery in the linked solar planning and on the settings of the Battery storage component:
Field | Where | Effect |
| Product data | Maximum state of charge. Several batteries are added together. |
| Product data | Maximum charging and discharging power. If the value is missing, autarc uses 0.5 × capacity. |
| Product data | Losses, split evenly between charging and discharging. If the value is missing, autarc uses 90 %. |
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| The battery charges from the grid up to this state of charge. The rest stays free for solar power. |
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| The battery never discharges below this state of charge. |
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| Allows the battery to supply the wallbox. Off by default. |
The losses are shown as Energy losses under Solar yield (yearly).
Viewing the energy flows
In the simulation's Charts tab, choose a period in the Energy flow section: Year, Month or Day – at a Simulation resolution of 1 minute also Hour. Use the arrows to move to the previous or next period. Clicking the date opens a calendar where you pick a month or day directly; Today jumps to today's date.
Next to it you switch between three views:
Bar: shows consumption and generation as bars per month, day or time step. Click a bar to zoom into that period.Sankey: shows how much energy flows from which source to which consumer. The width of a band corresponds to the amount of energy.Flow: shows the energy flows as an animated diagram between solar system, battery, grid and consumers.
Below Year/Month/Day/Hour, the slider selects a part of the period, e.g. one hour of a day. With the play button (▶) you play the simulation: the parts run one after another, and at the end it continues with the next period. This shows, for example, how generation, battery and grid consumption develop over a day, hour by hour. This works in all views.
In a scenario you see the energy flows of the planned variant, in the Current tab those of today's situation.
Frequently asked questions
Why is a lot fed in during summer and a lot drawn from the grid in winter?
In summer the solar system often produces more than can be used and stored – the surplus goes into the grid. In winter it produces little, while a heat pump needs a lot of electricity. A battery balances day and night, but not summer and winter.
Why isn't the battery full every day?
The battery only charges with the surplus left after direct self-consumption. On cloudy days or with high consumption, that isn't enough to fill it. In the Flow view with the period Day, you can see this hour by hour.
Why doesn't the battery supply the wallbox?
With Maximise self-consumption, the battery is reserved for the household and the other consumers. The wallbox charges directly with solar power and otherwise from the grid. With Tariff arbitrage you can turn on Battery may supply wallbox.
What isn't simulated (yet)?
Dynamic exchange electricity prices, feed-in limits or curtailment, blocking periods and feeding electricity from the battery into the grid are currently not simulated.