Small flat with a shared roof share

Low use, small share of roof.

Fictional company. Every figure on this site is an illustrative example.

Concept scenario, not an installed system

The scenario

A small share of a shared roof makes enough for a flat that is empty during the day. Most of the energy is exported, so the real benefit depends on rules this site does not model.

Read export rules before sizing.

Inputs: 2,500 kWh a year, 12 m2 of roof, Warm south, no battery
System size: 2.1 kWp
Yearly generation: 2,200 to 2,750 kWh
Met on site: 30%
Annual energy value (illustrative range): EUR 250 to EUR 410

Open this scenario in the calculator

A clear midday sky. — Generated illustration, illustrative. Not a Lumivane installation.

What drives this chart

Ranked by weight on the picture. Nothing here is hidden in a tooltip.

Inputs you can change

d1 System size: in kWp, from the page. Peak output is 80% of this in a clear sky.
d2 Sky: clear 100%, bright cloud 60%, overcast 25%. A multiplier on generation, all day.
d3 Battery: in usable kWh, from the page. Takes surplus at up to half its size in kW.

Fixed constants

d4 Shape of the day: sunrise 06:00, sunset 20:00. A sine curve raised to the power 1.3 between those hours.
d5 Home load: 0.35 kW base, plus morning, noon and evening bumps. A typical profile, scaled to the yearly use on the page.
d6 Battery losses: 90% in, battery starts with 1 kWh. Usable capacity is 90% of the nameplate.
d7 Order of use: home, then battery, then grid. The battery never sends energy to the grid.

Caveats

d8 One illustrative summer day: not a forecast. Real days differ with shade, tilt, season and temperature.

A day in this scenario

Time of day

A sunny day in this scenario: 2.1 kWp, no battery (illustrative)

The roof makes more than the house can use.

13:00: the roof makes 1.7 kW. The house uses 0.4 kW of it and 1.3 kW goes to the grid.

SkyClearBright cloudOvercast

Solid band: straight from the roof to the house
Dashed band: in or out of the battery
Dotted band: to or from the grid

Day totals: 13.6 kWh generated, 4.2 to the home, 0.0 to the battery, 9.5 to the grid.

A sunny day in this scenario: 2.1 kWp, no battery (illustrative)
Time	Generated (kW)	Home (kW)	Grid (kW)
06:00	0.0	0.0	-0.3
07:00	0.2	0.2	-0.4
08:00	0.6	0.6	-0.1
09:00	0.9	0.3	0.7
10:00	1.2	0.3	1.0
11:00	1.5	0.3	1.2
12:00	1.6	0.4	1.2
13:00	1.7	0.4	1.3
14:00	1.6	0.3	1.4
15:00	1.5	0.3	1.2
16:00	1.2	0.3	1.0
17:00	0.9	0.3	0.7
18:00	0.6	0.6	-0.3
19:00	0.2	0.2	-0.7
20:00	0.0	0.0	-0.9

Battery: positive is charging, negative is discharging. Grid: positive is exported, negative is imported.

These scenarios are fictional. No customer, installation or capacity is implied.