Why self-consumption is the first lever of profitability
In French-speaking Switzerland, the electricity purchase rate is CHF 0.20–0.30/kWh and the injection rate (surplus purchase) is CHF 0.07–0.10/kWh. The difference is a factor of 3–4x. Concretely: 1 kWh self-consumed brings you 3–4 times more than 1 kWh injected. Maximizing self-consumption is therefore the main lever for profitability, even before increasing the size of the installation.
Lever 1: Manual shift of large devices (free)
Start washing machine, dishwasher and dryer between 10h and 16h. These devices consume 1–2 kWh per cycle and their start time is flexible. Typical gain: +8–15% self-consumption. Tip: use the built-in timer of your devices the evening before by programming on 10h30 the next morning.
Lever 2: Thermodynamic electric water heater (investment CHF 800–1 500)
An electric resistance water heater uses 2–4 kWh to heat water for a family. With a programmer or a dry contact controlled by the EMS, it only heats when production exceeds instantaneous consumption. The water heater becomes a “thermal storage” which captures solar surpluses. Estimated gain: +5–10% self-consumption depending on the size of the household.
3 lever: EV charging during the day (via smart terminal)
A charging station with control (Wallbox Pulsar Plus, ABB Terra AC) can be programmed or controlled by the EMS to charge exclusively from solar surplus. For an EV traveling 40 km/day (≈ 8 kWh), recharging over 4 solar hours at 2 kW covers the daily requirement. Self-consumption gain: up to +15–25% depending on daily mileage.
Lever 4: EMS and automatic piloting (investment included in hybrid inverter)
An EMS (Energy Management System) constantly monitors production vs consumption and automatically triggers connected devices (via connected sockets, RS485 signals or dry contact). Gain: +10–20% vs. manual shift alone. Huawei's EMMA is the most used in French-speaking Switzerland — it manages LUNA2000, HUAWEI CHARGER-AC terminal and compatible water heater.
Lever 5: The correct sizing of the installation
Paradoxically, an installation that is too large reduces the rate of self-consumption (a lot of injection). The economic optimum in Switzerland is to size for an annual production equal to 100–130% of your annual consumption. For 5 000 kWh/year of consumption: installation of 5–6.5 kWp. With battery: 7–9 kWp.
Lever 6: Battery 8–12 kWh (investment CHF 5 000–9 000)
The battery is the most efficient lever but also the most expensive. She stores the day's surplus for the night. Self-consumption gain: +25–40% points (from 35% to 65–80%). ROI of the battery alone: 10–15 years. Recommendation: Consider battery only after maximizing levers 1-5.
7 lever: Monitoring and continuous adjustment
Install and consult your inverter monitoring application (FusionSolar, SolarWeb, Enlighten). By analyzing weekly data, you identify the hours when you inject the most (noon on weekends: take the opportunity to do the laundry). This active monitoring can be worth 3–5% additional self-consumption without any investment.