Solar panels and home automation: using your surplus

The problem: production and consumption don't line up

With no control, a large share of what the panels produce isn't used in the home at that moment and is exported to the grid. Then in the evening, when the home does use energy, it buys it. The aim is to bring the two curves closer together.

First, measure

It all starts with an energy meter in the panel that knows, at every moment, how much is being produced, used, exported or imported. Many inverters provide this; the automation system reads it and acts on it.

Which loads can be shifted

• Hot water: the cylinder or heat pump tank is a cheap "thermal battery". Heating water at midday with surplus is the most cost-effective move.
• Heating and cooling: pre-heat or pre-cool the home a few hours ahead, using its thermal inertia.
• Electric vehicle: charge with whatever power is spare at each moment, rather than at a fixed rate.
• Appliances: washing machine, dishwasher or dryer during sunny hours.
• Pool: the filter pump and heat pump.

How the system decides

You set a priority order. For example: battery first, then hot water, then the car, and finally heating. When there's surplus, loads switch on in that order; when a cloud passes, they switch off in reverse. Weather forecasts and tariff periods can be taken into account too.

With or without a battery

A battery stores surplus for the night and may provide backup in an outage, depending on the equipment. It doesn't replace load management: the most efficient approach is to use directly what you can and store the rest.

Staying within your contracted power

The same measurement works the other way: if the home nears its power limit, the system reduces car charging or delays a load, so the supply doesn't trip.

What you see in the app

• Production, consumption and balance in real time.
• Self-consumption percentage by day, month and year.
• Which load is using the surplus.

In a mountain climate

In winter production drops and snow can cover the panels; summer and the shoulder seasons are when there's most surplus. The strategy needs to adapt to the season.