Panels, face by face
The automatic layout fills the roof faces that point south, east or south-west and leaves the others empty. Per face you can fill, clear, or add and remove panels one at a time; every fit keeps 0.3 m from each edge and clears every roof object. The default module is 420 W, 1.134 × 1.762 m and 21 % efficient; a selected installer's card re-simulates with its own panel. You can set a face's tilt from 0 to 60° and the roof material per building; both change the yield and go to the installer with your request.
A battery, four strategies, one winner
Battery sizes are 5, 10, 15 and 20 kWh; each charges and discharges at half its capacity per hour, so a 10 kWh battery is a 5 kW battery. Each size is simulated with four strategies over the whole year: own solar first (charge from the roof, discharge to the house), cheap-hour charging from the grid, lower power peaks for an effekttariff, and combined. Every battery loses 10 % per round trip and keeps a 10 % reserve.
The strategy with the highest saving per year at your prices wins; a tie goes to the simpler one. That is 1 + 4 × 4 = 17 simulation runs per change. You can also pick a strategy yourself and read the table of all four.
An electricity provider's battery program
A provider can pay you to control part of your battery for the grid's frequency reserve. We list a program only when a public page states its terms. Today that is one: Flower Hub, 57 kr per kW and month (September 2026), for batteries behind Huawei SUN2000, SAJ H2/HS2 or Sungrow SH inverters, with an hourly-price contract run by Flower's partner Rebel Flex, in SE1–SE4; read on 8 October 2026. The page does not say how much of the battery is reserved, so we reserve half its power. Switch it on and the income per year is shown next to the saving.
An electric car, five ways to charge
Say yes to a car and type the km per day (30 by default, up to 300); the car uses 0.19 kWh per km. Then choose when it charges: when you plug in (19:00–06:00, evenly), the cheapest hours between plug-in at 17:00 and departure at 07:00, at night 22:00–06:00, fixed hours you set, or solar surplus first and then the cheapest hours. The charger is 2.3, 3.7, 7.4, 11 or 22 kW and caps each hour; what does not fit spills into the next cheapest hours. A table shows the cost per year of all five and the share of the charging that came from the roof.
Your household, by month and by hour
Pick a yearly use (apartment 3 000 kWh, small house 10 000, house 15 000, large house 25 000) or type your own. Then shape it: 12 monthly shares and a 24-hour day. Month presets: direct electric heating (winter 4–5 × summer), heat pump (2.8 ×), district heating (1.5 ×) and holiday house (most use in June–August). Day presets: home all day, away 08–17, or an evening peak. A month keeps at least 1 % of the year and an hour at least 5 % of a flat hour, the fridge and the ventilation. The year's kWh stays exactly what you typed, and the same day shape is used for every day: there is no weekday and weekend split.
Trees, roof objects and prices
Move, resize, copy or add trees; set a chimney's or a dormer's height; every change re-runs the shade. In the Prices panel, change the supplier markup, the energy tax, the grid company and its transfer fee, the export price and a peak charge; VAT stays at 25 %. Each edit goes on an undo stack, and your private link remembers all of it.
