Smart Consumer Units and Load Management for Solar Homes

Your solar panels generate most of their electricity in the middle of the day — exactly when most households use the least. Without some form of load management, that surplus flows to the grid for a modest export payment (typically 4–15p/kWh under the Smart Export Guarantee) rather than displacing grid electricity you would otherwise pay 24–30p/kWh for. A smart consumer unit or a dedicated load manager solves this mismatch automatically, detecting surplus generation and switching on high-demand appliances before the energy reaches the meter.

What Is a Smart Consumer Unit?

A smart consumer unit is an upgraded fuse board fitted with app-controlled circuit breakers, arc-fault detection interrupters (AFDDs), and — in the most capable versions — load management relays that can be triggered by your inverter's output signal. Unlike a standard split-load consumer unit, each circuit can be individually switched, monitored for real-time consumption, and scheduled or automated via a smartphone app or home automation platform such as Home Assistant.

In the UK, full smart consumer units are available from manufacturers including Hager (the Witty/flow ecosystem), Schneider Electric (Wiser Energy), and to a lesser extent Sunsynk (whose Solarbank hub integrates load control with the company's hybrid inverters). These combine metering, circuit switching, and solar-awareness into a single DIN-rail assembly. Prices for supply and professional installation typically range from £800 to £2,500 depending on the number of circuits, AFDD protection, and the complexity of the solar and battery integration.

Load Management Without Replacing Your Fuse Board

Most UK solar homeowners achieve effective load management without touching their consumer unit at all. A class of add-on devices — DIN-rail relays, power diverters, and smart plugs — sit between the consumer unit and individual appliances, reading generation data from a clamp meter on the solar feed and automatically switching loads on when surplus is detected.

Eddi by myenergi — the UK's Most Popular Solar Diverter

The Eddi is not a consumer unit replacement, but it is the single most widely fitted load manager on UK solar installations. It connects to your existing consumer unit via a standard 16 A or 32 A circuit and monitors generation in real time with a clip-on CT clamp. When surplus exceeds the minimum threshold (around 100 W), the Eddi proportionally diverts that power to an immersion heater or storage heater element instead of exporting it, with a maximum heater load of 3.68 kW. Two heater outputs can run simultaneously, letting you heat a hot-water cylinder and a towel rail from the same unit.

Supply cost for the Eddi v2.1 is around £200–£250 from trade suppliers, with a typical installation labour cost of £150–£250 for a qualified electrician. The total all-in cost of approximately £350–£500 makes it the most accessible entry point into solar load management. The Eddi pairs with myenergi's Zappi EV charger for a whole-home solar ecosystem, and both devices integrate with home battery storage systems via the myenergi hub.

Shelly Pro Series — Flexible DIN-Rail Relays

Shelly Pro devices are professional-grade Wi-Fi and LAN relays that mount inside a standard DIN-rail enclosure alongside your existing breakers. The Shelly Pro 4PM provides four independently switchable channels, each rated to 16 A (40 A total), with built-in energy metering per channel. When integrated with Home Assistant, Node-RED, or the native Shelly scripting engine, these relays can receive real-time surplus data from a solar inverter's local API or a Shelly EM current clamp and automatically activate a washing machine, dishwasher, or underfloor heating circuit whenever generation exceeds a set threshold. The Shelly Pro 4PM retails for approximately £80–£100, making a multi-load automation setup achievable for under £300 including CT clamps and installation labour.

Schneider Electric Wiser Energy

Schneider's Wiser platform targets homes that want deeper integration across heating, solar, and EV charging in a single app. The Wiser Energy Hub connects to individual clip-on load monitors on key circuits and to the household solar inverter, presenting a unified energy dashboard. Automated rules can shift heating schedules to align with forecast solar generation, and Schneider has added AI-assisted scheduling that learns household patterns to further optimise self-consumption. The Wiser ecosystem works with a compatible Schneider consumer unit or as a retrofit monitoring layer on an existing board.

How Load Management Works with Solar

All the approaches above share the same fundamental logic:

1. Measure generation — a CT clamp on the main solar feed or inverter output measures generation every few seconds.
2. Measure consumption — a second CT clamp (or the inverter's own export/import reading) tracks what the house is already using.
3. Calculate surplus — surplus = generation minus consumption.
4. Switch loads — when surplus exceeds the appliance's minimum demand, the relay or diverter activates it. When surplus drops below the threshold, it switches off or dims proportionally.

The result is that your hot water, for instance, is heated almost entirely by solar during summer months — effectively turning your cylinder into a thermal battery — without any manual intervention.

Integrating a Time-of-Use Tariff

Combining load management with a half-hourly tariff such as Octopus Agile amplifies savings further. Octopus Agile prices change every 30 minutes in line with wholesale electricity markets, falling as low as negative values (when you are paid to consume) on windy nights, and rising to 30–35p/kWh during weekday evening peaks in winter. A load manager configured with tariff awareness — available in Home Assistant via the Predbat add-on, or natively in myenergi's hub — can postpone heavy loads such as dishwashers and washing machines to the cheapest overnight slots when solar is unavailable, and activate them on solar surplus during the day. Households running this combination on a 5 kWp solar system with a 10 kWh battery have reported annual electricity bill savings of £1,800–£2,500 compared with a flat-rate tariff and no automation. Explore how your system size affects generation output with our solar panel cost by system size guide, and see how EV charging with solar fits into an automated load plan.

Part P and Electrical Safety Rules

Replacing a consumer unit is notifiable work under Part P of the Building Regulations (England and Wales). It must be carried out by an electrician registered with a government-approved Competent Person Scheme — NICEIC, NAPIT, ELECSA, or Stroma — and certified against BS 7671:2018 (18th Edition Wiring Regulations), now incorporating Amendment 4 which came into force in April 2026. The electrician must issue a full Electrical Installation Certificate (EIC) and a Building Regulations Compliance Certificate on completion.

Add-on devices such as the Eddi, Shelly Pro, or Wiser Energy Hub that connect to existing circuits do not require a full board replacement, but any new circuit run to accommodate them (for example, a dedicated 20 A radial for an immersion heater) is notifiable work and must be certified. Fitting a load management relay inside an existing consumer unit enclosure is similarly notifiable. Always engage a registered electrician for any work inside the consumer unit.

Choosing the Right Approach

For most households with an existing boiler-fed hot-water cylinder converting to solar, the Eddi represents the highest return on investment: immersion diversion is the single largest load management opportunity in a typical UK home, hot water accounts for roughly 20–25% of household energy use, and the Eddi's all-in cost of under £500 recovers in 2–4 years on a 4 kWp or larger system. If you also have or plan an EV, adding a myenergi Zappi charger to the same hub gives coordinated solar-first charging. If your priority is whole-home automation across many circuits — appliances, underfloor heating, EV, and battery — a full smart consumer unit from Hager or Schneider, or a Shelly Pro relay array managed by Home Assistant, will deliver more granular control, at commensurately higher upfront cost.