Inverter Customisation: Schedules, Limits & Reserves

When your installer hands over a new solar system, the inverter is typically set to factory defaults. Those defaults are safe and generic. They are rarely optimal for your tariff, your household routine, or your grid's export rules. Unlocking the four settings below can meaningfully improve your financial return.

Charge Schedules

A charge schedule tells the inverter when to charge your battery from the grid — as distinct from charging from solar. This matters on tariffs where electricity is significantly cheaper at certain times of day or night.

For example, on a tariff where off-peak electricity costs 8p/kWh and peak costs 28p/kWh, forcing the inverter to charge the battery to 80% between 00:30 and 04:30 and then discharge during the evening peak can save 20p per kWh used — without a single extra panel.

How to set it by brand:

• GivEnergy: EVC (External AC Charge) timer in the GivEnergy portal, settable per day of week
• Sungrow SH series: Grid charge time slot in iSolarCloud app or local web interface
• Huawei LUNA: Time-of-Use schedule in FusionSolar app
• SolarEdge + StorEdge: Charge from grid via the StorEdge interface in MySolarEdge

Export Limits

Many utilities and distribution network operators (DNOs) cap how much power a residential system can export to the grid. Common limits include:

→ Numbers speak louder: calculate your annual solar return and take the guesswork out.

• 3.68 kW per phase in the UK (G98/G99 rules)
• 5 kW in parts of Germany
• 0 W export (zero-export) required in some commercial districts across Asia and the Middle East

All major hybrid inverters support configurable export limits. Setting this incorrectly — or not at all — risks disconnection notices from your utility. The inverter measures total household export at the grid connection point (using a CT clamp) and throttles inverter output in real time to stay within the limit.

Zero-export mode is also used intentionally by homeowners who want to maximise self-consumption: every kWh generated is consumed locally or stored in the battery, and nothing goes to the grid.

Time-of-Use Optimisation

Time-of-use (TOU) optimisation goes further than a charge schedule. It builds a full 24-hour strategy:

1. Charge battery from solar during peak generation hours
2. Use battery power during evening peak tariff periods
3. Allow grid top-up during cheap overnight windows if battery is below a threshold
4. Export surplus during periods when the feed-in tariff is highest (where dynamic export pricing applies)

Inverters like the Fronius Gen24, GivEnergy AIO, and Sungrow SH series allow you to define up to six time slots per day, each with a different operating mode. Some models support automated TOU via integration with smart tariff APIs — Octopus Energy's Agile tariff integration with GivEnergy is a well-documented example.

Battery Reserve

Battery reserve (also called minimum state of charge or emergency backup reserve) is the floor below which the inverter will not discharge the battery under normal conditions. The battery holds this charge in reserve for grid outages or overnight minimum use.

Common configurations:

• Power cut reserve: Set 20–30% reserve to ensure the home has backup power during an outage
• Winter optimisation: Increase reserve in winter when overnight temperatures drop and solar generation is lower
• No reserve: Set 0% for maximum daily cycling — only appropriate where outages are rare and the priority is financial optimisation

Important: Lithium batteries (LFP chemistry in BYD, Pylontech, and most modern storage) tolerate daily full cycles well. Older NMC chemistry batteries benefit from a higher reserve to preserve cycle life.

→ Your bill, your roof, your result — find out your solar savings now.

Settings Interaction: Getting the Logic Right

These four settings interact. A common misconfiguration is setting a high battery reserve while also enabling a grid charge schedule — the inverter charges from the grid to 80%, but the reserve floor is 80%, so nothing is ever discharged during peak periods. Always test your configuration over a 48-hour period and check your monitoring app for unexpected grid import events.

Comparison: Configuration Depth by Brand