Solar diverter: stop giving your surplus away to the grid
Every kWh you export earns you a few cents. The same kWh in your hot water cylinder is worth five times more.
This is the most profitable accessory of any solar installation — and the one the public knows least about.
The problem: surplus sold off cheap
As soon as your panels produce more than the house is using, the surplus goes to the grid. Under a surplus-sale arrangement it earns a few cents per kWh — while the kWh you buy back in the evening costs five to six times as much. Every kWh exported instead of used at home is an opportunity lost.
The answer: divert the surplus
A solar diverter constantly measures what is heading out to the grid and steers that surplus — watt by watt, by modulating the power — into something useful, almost always the hot water cylinder. The result:
- Your cylinder heats free, on sunshine, instead of running overnight
- Export to the grid drops almost to zero
- Hot water becomes your cheapest battery: storing 3 kWh in water costs nothing beyond the diverter itself
What to look at before buying
- How finely it modulates: a proper diverter modulates watt by watt (via a triac); it does not simply switch on and off
- Whether it stays local: many commercial diverters route through a cloud app, with all the same drawbacks as inverters — see our guide on going cloud-free
- Tariff support: handling of off-peak periods, so heating can be topped up overnight when the sun has not been enough. In France this means reading the Linky smart meter's peak and off-peak signal
- Home automation: being able to monitor and control it from Home Assistant, over local MQTT
Our Solar Router
The heliolocal Solar Router is designed and built in Hirson, northern France: triac modulation, several measurement points, Ethernet and WiFi, fully local MQTT, and native handling of the Linky meter's off-peak signal. No cloud app, no subscription — it works for you, at your place.
Questions about your own setup? Write to us, or use the calculator to estimate your production.
Free assessment and quote, quality hardware, and 100% local monitoring with no subscription — your data stays with you.