Reading the results and the graphs

When a run finishes you land on the results page, the last step of the wizard. It shows one run at a time, and with several you pick one from a strip of saved runs. A card called What was simulated, near the bottom, recaps that run’s inputs, including its weather and its dispatch method (how the model decides each hour when the battery charges and when you buy from or sell to the grid). Read it first when you compare runs.

The key figures

Energy is in kWh, kilowatt-hours, the unit on your electricity bill. A 1 kW heater running for an hour uses 1 kWh.

Under HP electricity you see the heat pump’s COP (coefficient of performance) over the year: the heat it delivers divided by the electricity it uses while running, without standby (the SCOPon of the EN 14825 standard). A COP of 3 means three units of heat for each unit of electricity. When no fuel is burned there is also a system COP that counts the standby and the backup heater too. The gap between the two shows how far the backup pulls efficiency down, and in a house that needs little heat, how much the standby weighs.

Annual cost covers grid electricity only. Fuel for a boiler appears in kWh but is not priced, and equipment cost, maintenance, battery ageing and financing are left out.

A panel called Comfort & sanity checks may appear below the figures. It flags results worth a second look, such as an indoor peak above 28 °C, a minimum below 18 °C, or a year with no heating at all. These are rules of thumb that point at inputs to check.

Indoor temperature is the average air temperature of the occupied zones, weighted by floor area. Unheated spaces such as an attic or garage are left out.

Monthly energy use

Stacked bars show electricity by use, in kWh per month: Heating, Cooling, Hot water, Household and, if you have one, EV charging. A use appears only when it carries energy over the year. Heating here is the electricity used to heat (heat pump plus backup heater), while the Heating figure above is the heat itself, so the two should not match. PV production, the output of your solar panels (PV is short for photovoltaic), is a line over the bars because it is generation, not consumption. Fuel is not in this chart.

Daily energy balance

Three lines in kWh per day: PV production, Grid import and Grid export (dashed).

Energy flows

This diagram follows a year of energy from sources (Grid Import, PV Panels, Fuel) through equipment (Heat Pump, Backup Heater, Boiler, Battery) to uses (House Heat, House Cool, DHW, Household, Grid Export). DHW is domestic hot water, the water from your taps and shower. Solar hot-water collectors, a pool and an electric car appear too when you have them. Hover for annual kWh.

Widths use a square-root scale, which squeezes big flows so small ones stay visible. A flow twice as wide carries four times the energy, so compare flows by their hover values, not by eye. Electricity keeps the colour of its source, so you can follow PV or grid power across the diagram. Heat, cooling and hot water have their own colours.

Flows below 50 kWh, or below 1 % of the largest heat, cooling or hot-water flow if that is more, are dropped to keep the picture readable. Equipment you configured that did not run is greyed out and marked configured · unused.

Your home energy system

This panel draws the same annual data as a schematic of your system. Click equipment, or choose it from the list, to follow its connections and see its annual rows and main specifications.

The rows keep different things apart: a heat pump’s electricity in is separate from its heat out, and a battery’s charging from its discharging. The Elec Bus, the shared electrical connection that sources feed and equipment draws from, has no total, because adding what goes in to what comes out would mislead. Drag cards to rearrange them; your browser remembers the layout, and Reset layout puts it back.

Hourly trajectory

Temperature is on the left axis in °C: Indoor °C (solid) and Outdoor °C (dashed). Power is on the right axis in kW, the rate of use at one moment, where kWh is the amount used over time. The power lines are HP heat kW, HP cool kW, PV kW and Grid kW. The first two are the electricity the heat pump draws while heating and while cooling, not the heat or cooling it delivers. Grid kW is the power bought from the grid.

Drag the handles under the chart to pick a period. It opens on the first 30 days. Up to 20 days you see every simulated hour. Beyond that the chart shows daily averages, which smooth peaks, and a line above the plot says which mode you are in.

Hourly CSV

A run keeps 8,760 hourly values, which is 365 days of 24 hours (29 February is left out in a leap year). They drive the chart and can be exported as a CSV file, a plain table that opens in a spreadsheet, with one row per hour and one column per series. The first column is the hour number, 0 to 8759, with no date, so hour 0 is the first hour of 1 January. Most column names end in their unit, such as W or kW, so check before you sum. If a run’s hourly data was not kept, the page says so and shows its key figures only.

Limits of the model

• Indoor temperature is an average over zones, not the temperature of one room.
• Where grid import feeds several uses in the same hour, the split between them is proportional. That is an accounting convention, not a measured path.
• Results come from one weather year, a typical year (a made-up year that looks ordinary, built from many real ones) or one real year, and move with it.
• Compare runs under the same assumptions, as Comparing scenarios fairly explains.