In the system simulation you model a building's current state and compare it with one or more planned variants.

You can combine all components of an energy system: solar system, battery storage, household, heating system (e.g. heat pump, gas or oil), wallbox / EV and air conditioning.

For every variant, autarc simulates a full year – hourly by default, or in 30-, 15- or 1-minute steps if you prefer – and works out how much solar power is generated, used directly, stored, fed into the grid or drawn from it, and how much electricity the heat pump, wallbox and other consumers need.

That year is then projected over the whole analysis period – 20 years by default, or the period you have set – including energy price increases and recurring costs.
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This gives you the self-consumption rate, self-sufficiency, costs and the profitability shown in your offer.

The simulation is split into tabs:

In every tab you'll find the system's components on the right – e.g. Solar System, Battery storage, Household, Heating system, Wallbox / EV and Air conditioning. Use the toggle to add a component to that tab or remove it. Click the arrow in front of a component, or the component itself, to expand its details.

What matters is which tab a component is switched on in:

You can also simulate differences without adding new components – e.g. a different household consumption, a different Usage pattern, or switching between a dynamic and a non-dynamic electricity tariff. Such changes only apply to that scenario; Current, other scenarios and the project stay unchanged.

Examples:

The solar system and the wallbox can each be linked to their own planning variant in every tab. You'll find the selection at the top of the expanded component:

Click Solar planning or Wallbox planning to jump straight to the linked planning.

Heating system and Air conditioning use the project's heating and AC planning. Heating planner (in scenarios with the type Heat pump) and AC planner take you straight there.

Every scenario is compared with Current by default. Use Compare with: at the top right to pick another scenario instead – e.g. “Scenario 1” against “Scenario 2”. Charts and KPIs then show both variants side by side, including the percentage change.

The Current tab has no comparison: it only shows the energy flow and current costs. Profitability and return on investment (ROI) are only shown in scenarios.

You can choose Hourly, 30 minutes, 15 minutes or 1 minute resolution, meaning the simulation will calculate values for each step for one year.

The resolution applies to Current and all scenarios in the project so they stay comparable. In a scenario it is only displayed (Set in the Current tab). Click the pencil icon to go straight back to the Current tab.

Set values you use for almost every project once, centrally:

These values are applied to every new simulation and can be adjusted per project – the simulation resolution in the Current tab, the other values in the respective simulation. Existing simulations stay unchanged.

Instead of a standard profile you can use your own load profile for any consumer – either uploaded from measured data or drawn yourself.

If you have measured consumption data (e.g. from the grid operator or a smart meter), you can use it instead of a standard profile:

No file to hand? Under Templates: you'll find template for any resolution. Download and paste your values into the file and upload it.

Without measured data you can also create a profile yourself – e.g. for a wallbox that only charges at night, or an unusual household behaviour.

The drawn curve is scaled to the annual consumption you entered.

Besides the fixed components you can add your own consumers and producers with their own load profile – e.g. a pool pump, a sauna, a production line, or other generators such as a wind turbine or a generator.

Like the fixed components, a custom consumer or producer in the Current tab counts as already existing – so an existing wind turbine already lowers today's costs. For a producer, Include in KPIs decides whether its generation counts towards self-sufficiency and the self-consumption rate, or whether only the solar system is shown.

In the Energy flow section you can switch the period between Year, Month and Day. At a resolution of 1 minute, Hour is also available. Use the arrows < / > or the date picker to move through the year.

This lets you see, for example on a summer day, how the battery charges at midday and supplies the household in the evening.

In the Energy flow section you can switch between the views Flow, Bar, Sankey and Table. What each chart shows is explained in Energy Flows.

The same calculation runs for Current and every scenario – each with the components switched on in that tab:

Switch the component on in the Current tab.

For an existing solar system, choose the matching planning in the Solar System component under Solar planning.

For an existing heat pump, set the Heating system type to Heat pump – with an optional Heat pump model, annual consumption, tariff and, if you like, your own load profile.

For an existing wallbox, choose the matching planning in the Wallbox / EV component under Wallbox planning.

For existing air conditioning, switch on the Air conditioning component and enter its annual consumption – or open the AC planner to base it on the project's AC planning.

Also switch the component on in the scenarios where it keeps running – it counts there as existing, not as a new investment.

Profitability, payback and ROI only arise from comparing a planned variant with Current. The Current tab therefore only shows the energy flow and current costs. Switch to a scenario to see the economics.

Changes in the Current tab overwrite the project data (note Values are applied globally) – e.g. the household consumption, or the current heating system type and consumption which is also used elsewhere in the project. Values changed in a scenario are not affected.

Via the … menu on the scenario's tab, where you'll also find Delete simulation. The Current tab can be neither renamed nor deleted.

For most single-family homes, Hourly is the right choice: standard profiles and weather data are hourly, so a finer resolution gives the same results.

A finer resolution pays off when you have measured data in 30-, 15- or 1-minute values – e.g. for commercial and industrial customers, or in markets billed in 30-minute intervals. Short load peaks that would disappear in an hourly value become visible.

Note that the calculation can take longer at finer resolutions (1 minute = 525,600 time steps per year).

Standard, Home Office, Mainly morning, Mainly evening, Winter peak, Summer peak and Custom load profile. The variants shift consumption within the day or the year – the annual consumption always stays the same.

The simulation uses a reference year of 365 days (no leap day) in standard time, i.e. without daylight saving time. Public holidays are treated like Sundays.

With the control scheme Maximise self-consumption, the battery only supplies household and heat pump. The wallbox gets solar power directly and otherwise grid power. With the control scheme Tariff arbitrage you can enable Battery may supply wallbox.

Dynamic spot-market electricity prices, feed-in limits or curtailment, blocking periods, and feeding battery power into the grid are not simulated at the moment. The battery only charges from the grid with the control scheme Tariff arbitrage.

Please get in touch if you have requests or feedback.