A 3.6kWp hybrid PV/Battery inverter and charger will be the largest permissible under the G98 requirements for grid tied microgeneration. Combined with the 6kWh battery capacity it should cover most of your requirements for six months of the year but surplus solar in the winter months can be an issue. One useful feature is the option with many chargers to have some house circuits configured to use the emergency backup facility in a power cut. These will need to be carefully chosen to avoid overloading the inverter so usually are lighting and fridge/freezer circuits. 

One option is to move to an ev tariff for your electricity. Octopus Go is a tariff that costs 5p/kWh from 0:30 to 04:30 every night. This is not solely a tariff for ev owners and if you have a battery system it allows you to charge up at 5p per unit which you then use the rest of the day to cover base load when solar output is low. All this is usually simple to program. Obviously any demand exceeding the 3kW inverter output capacity will still need a share of grid power at higher cost. These systems are designed to maximise battery life by preventing discharge to a damaging level and can be expected to last 10 years. If you want a separate battery charger system it is the combined capacity that is available. This however must be installed under G99 requirements. This might mean on a sunny day with 3kW output from solar and 3kW output capacity from the battery system your 9kW shower only uses 3kW from the grid i.e. ⅓rd of normal cost. A 10 minute shower would only take 0.5kWh (1/6 X 3) from the 6kWh battery so leave plenty to cover evening base load occasional kettle etc. Adding additional solar capacity may not be cost effective unless you have ev and or AHP heating when compared to cheap overnight tariff for charging. There are solar diverters available that boost the hot water immersion heater from solar surplus and these are a good option without a battery system to make use of the surplus. Some ev chargers also can use surplus so again are a good option if you have a larger PV system.

There's a lot of content on line that can help with decision making. I have a 2.6kWp solar system that even in the north of Scotland provides our baseload during daylight in all but the cloudiest of days most of the year. This summer we have had sufficient surplus to heat the water tank via a diverter almost every day. I'm hoping the battery inverter systems reduce in price as battery technology develops and costs reduce. Given the present cost per unit it is probably cost effective especially if the system lasts 10 years.

A 3.6kWp hybrid PV/Battery inverter and charger will be the largest permissible under the G98 requirements for grid tied microgeneration. Combined with the 6kWh battery capacity it should cover most of your requirements for six months of the year but surplus solar in the winter months can be an issue. One useful feature is the option with many chargers to have some house circuits configured to use the emergency backup facility in a power cut. These will need to be carefully chosen to avoid overloading the inverter so usually are lighting and fridge/freezer circuits. 

One option is to move to an ev tariff for your electricity. Octopus Go is a tariff that costs 5p/kWh from 0:30 to 04:30 every night. This is not solely a tariff for ev owners and if you have a battery system it allows you to charge up at 5p per unit which you then use the rest of the day to cover base load when solar output is low. All this is usually simple to program. Obviously any demand exceeding the 3kW inverter output capacity will still need a share of grid power at higher cost. These systems are designed to maximise battery life by preventing discharge to a damaging level and can be expected to last 10 years. If you want a separate battery charger system it is the combined capacity that is available. This however must be installed under G99 requirements. This might mean on a sunny day with 3kW output from solar and 3kW output capacity from the battery system your 9kW shower only uses 3kW from the grid i.e. ⅓rd of normal cost. A 10 minute shower would only take 0.5kWh (1/6 X 3) from the 6kWh battery so leave plenty to cover evening base load occasional kettle etc. Adding additional solar capacity may not be cost effective unless you have ev and or AHP heating when compared to cheap overnight tariff for charging. There are solar diverters available that boost the hot water immersion heater from solar surplus and these are a good option without a battery system to make use of the surplus. Some ev chargers also can use surplus so again are a good option if you have a larger PV system.

There's a lot of content on line that can help with decision making. I have a 2.6kWp solar system that even in the north of Scotland provides our baseload during daylight in all but the cloudiest of days most of the year. This summer we have had sufficient surplus to heat the water tank via a diverter almost every day. I'm hoping the battery inverter systems reduce in price as battery technology develops and costs reduce. Given the present cost per unit it is probably cost effective especially if the system lasts 10 years.