Raising self-consumption: seven levers, ranked by effect

Why self-consumption is worth so much

An exported kilowatt hour currently earns 7.86 cents. A self-consumed one saves 35. The ratio is more than four to one — and every price rise widens it.

On a typical 10 kWp array at 40 percent self-consumption, each additional percentage point is worth about €27 a year. Ten points is €270 — every year, for 25 years.

The levers, ranked

First: charge the electric car at home, and at midday rather than in the evening. A car doing 13,000 km a year draws around 2,600 kilowatt hours. Charging half of that from your own generation raises self-consumption by 1,300 kilowatt hours — more than any other single measure.

Second: hot water via an immersion heater. Heating 300 litres from 20 to 60 degrees stores around 14 kilowatt hours, at a cost of a few hundred euros. No battery comes close to that price-to-capacity ratio.

Third: run the heat pump at a raised flow temperature around midday. The building itself becomes the thermal store.

Fourth: put the washing machine, dryer and dishwasher on a timer or delayed start into the midday hours. Three cycles a week is about 150 kilowatt hours a year.

What helps less than people think

Smart plugs with app control almost always fail on attention. What does not happen automatically stops happening after three weeks. A €9 mechanical timer beats a €90 app because it demands no decision.

Optimising lighting does nothing for self-consumption either: light is needed when the sun is not shining. The effect is real, but it lowers consumption rather than shifting it.

Know your base load

Before shifting anything, find out what runs permanently anyway. Read the meter twice an hour apart at night, with every deliberate load switched off. The difference is your base load.

Below 120 watts is good; above 250 watts points to avoidable permanent loads. That base load is also the floor a balcony solar system covers reliably — and therefore the most important number when sizing one.