How Solar Panels Generate, Store and Export Energy
Solar panels do not produce the same amount of electricity every hour or every month. The best results come from understanding when your home generates energy, when to use it, when to store it and when exporting it can be worth more.
Generation follows daylight. Your energy strategy follows the clock.
Panels begin generating after sunrise, normally build towards their strongest output around the middle of the day and reduce again towards sunset. Cloud, shade, roof direction, temperature and the season all influence the actual output.
Cheap-rate charging
If the forecast is poor or winter demand is high, a battery may be topped up during a low-cost tariff window.
Solar starts supplying the home
As daylight strengthens, solar reduces the electricity being imported from the grid.
Generation is often highest
The home uses solar first. Surplus power can then charge the battery, heat water or be exported.
Save or export
The best choice depends on the battery level, evening demand and the value of the export tariff.
Use stored energy
As solar fades, the battery can supply the home and reduce expensive peak-time imports.
Use it, store it or export it?
The correct order is not identical for every household or tariff, but a well-configured system normally gives each generated unit the most useful job.
Use solar directly
Running appliances while the panels are generating usually avoids buying a unit of electricity at the full import price. Washing machines, dishwashers, immersion heaters and EV charging can often be moved into productive daylight hours.
Store what you need later
A correctly sized battery holds daytime surplus for the evening and overnight. In winter it can also store cheaper off-peak grid energy for use during more expensive periods.
Export genuine surplus
Once the home is supplied and enough energy has been retained for later, surplus can be sold. With some tariffs, deliberately saving energy for a higher-value export window may produce a better financial result.
Summer surplus can help pay for winter electricity.
A solar system should be assessed across a full year—not judged from one bright day or one dark month.
Generation rises quickly
Longer days can produce strong output while household heating demand is falling. Batteries often reach full charge earlier and export begins to increase.
Maximum daylight and surplus
Long days create the greatest opportunity for direct use, water heating, EV charging and export. A well-sized array may generate considerably more than the home uses during daylight.
The strategy starts changing
Shorter days reduce solar yield. The battery schedule may need adjusting so valuable stored energy is kept for evening demand.
Cheap charging becomes important
Solar still contributes, but overnight tariff charging can help the battery protect the home from expensive daytime or peak-rate imports.
Tariff choice can change when energy is worth the most.
Octopus offers several import and export arrangements. Availability, compatibility and rates can change, and some prices vary by region, so customers should always check their postcode and current terms before switching.
| Tariff | How it works | Best suited to | Current position |
|---|---|---|---|
| Octopus Flux | Three-rate import and export tariff. The super-cheap period is 02:00–05:00 and the peak period is 16:00–19:00, in UK local time all year. | Solar-and-battery homes able to schedule charging and discharging. Actual unit rates are postcode-dependent and flexible. | Available |
| Intelligent Octopus Flux | Octopus automatically controls a compatible battery, charging when appropriate and exporting during valuable periods, including the 16:00–19:00 peak window. | Customers wanting automated control with a currently compatible battery. | Temporarily unavailable |
| Outgoing Octopus | A simple flat export payment, currently advertised at 12p per kWh. | Customers who want straightforward export payments without scheduling around a peak window. | Variable tariff |
| Prime Outgoing | Currently advertised at 16p per kWh from 16:00–19:00 and 9p per kWh at other times. | Battery owners who can shift surplus export into the evening peak period. | 12-month formula |
| Agile Outgoing | Half-hourly export prices follow day-ahead wholesale rates and are uncapped. | Customers with storage and active or automated control who accept variable prices. | 12-month formula |
Tariff information checked 6 September 2026. Intelligent Octopus Flux is currently described by Octopus as temporarily unavailable. Prices, eligibility and compatible batteries can change. See the official Octopus Flux page and official Outgoing Octopus page for current postcode-specific terms.
A battery is measured in kWh—but power output matters too.
A large capacity is not automatically the best choice. We look at how many kWh the home normally uses after sunset and how many kW the battery and inverter can deliver when several appliances operate together.
Modest evening demand
Often considered for lower-use homes that mainly need to cover lighting, refrigeration, entertainment and normal overnight baseload.
Example only—usable capacity and discharge power vary by product.Family or higher evening use
May suit homes with greater evening demand, regular cooking loads, longer overnight coverage or more solar surplus to retain.
The inverter must also be able to supply the required peak load.High-use and future-electric homes
Can be appropriate for substantial consumption, heat pumps, EV charging, all-electric properties, extended backup or larger commercial-style loads.
Larger systems require careful tariff, DNO and power-flow design.Why we do not start with a standard package.
For a suitable property, a carefully designed combination of solar panels, battery storage and the right tariff may reduce annual grid electricity costs by up to approximately 90%.
This is a design target, not a guarantee. The result depends on roof area and orientation, shading, consumption, when electricity is used, export permission, weather, equipment settings and future tariff rates. The standing charge still remains.
We size the system around your actual electricity use.
- Annual consumption: how many kWh the property buys across twelve months.
- Time of use: whether demand occurs during daylight, in the evening or overnight.
- Roof potential: orientation, pitch, shading and practical panel capacity.
- Battery capacity: enough usable kWh to cover realistic non-solar periods.
- Battery power: enough kW to support the appliances operating together.
- Future demand: EVs, heat pumps, electric heating, hot-water diversion and home extensions.
- Tariff strategy: the balance between avoided import costs, cheap charging and export income.
What should the system do today?
Sunny day forecast
Leave enough battery space to capture midday surplus. Run flexible appliances during productive solar hours.
Poor winter forecast
Consider cheap overnight charging so the battery is ready to cover expensive daytime and evening use.
High export window
Retain sufficient energy for the home, then export planned surplus if the payment exceeds the value of saving it.
EV or heat-pump demand
Coordinate large loads so they do not unnecessarily empty the home battery or force avoidable peak-rate imports.
Understanding the numbers.
Do solar panels work on cloudy days?
Yes. They generate from daylight rather than heat, although output is normally lower under heavy cloud than in strong direct sunlight.
Should I always fill the battery before exporting?
Not necessarily. If export is unusually valuable, planned export may be worthwhile. The decision depends on what electricity would cost to buy back later and how much stored energy the home still needs.
Can summer solar be stored for winter?
Not physically in a normal home battery. Batteries usually shift energy by hours or days. However, summer export payments can contribute towards winter import costs.
Does a bigger battery always save more?
No. An oversized battery may spend long periods partly empty, while an undersized or low-power battery may not cover the home’s demand. Capacity, discharge power, solar generation and tariffs must be considered together.
Will every property reduce its electricity bill by 90%?
No. “Up to 90%” describes the potential for suitable, carefully designed installations. Mr Solar provides a property-specific generation and usage assessment rather than promising the same saving to every customer.
Let us design the system around your home—not a panel package.
Mr Solar assesses your annual usage, daytime demand, roof, battery requirements, future EV or heating loads and tariff options before recommending equipment.