When a solar PV system generates more electricity than the home can use at that moment, the surplus needs somewhere to go.
It may:
- charge a battery
- charge an EV
- heat water
- supply another flexible load
- export to the grid
Export is not automatically wasted electricity.
Depending on the tariff and the wider system design, selling surplus electricity back to the grid can be one of the most valuable things the solar system does.
Solar export is what remains after the home, battery and other controllable loads have taken what they can use.
And the aim should not simply be to eliminate export.
The aim is to decide which surplus kWh are worth using, storing or selling.
What Is Solar Export?
Solar export is electricity that flows from the property back into the grid.
It happens when solar generation is higher than the electricity being:
- used by the home
- stored in the battery
- sent to other controllable loads
For example, solar generation of 5 kW, home demand of 2 kW and battery charging of 2 kW leaves 1 kW that can be exported.
Solar export is surplus electricity leaving the property.
Solar Generation Is Not the Same as Solar Export
A solar array producing 6 kW does not mean the property is exporting 6 kW.
Some of that electricity may already be being used.
For example, solar generation of 6 kW, home demand of 2 kW and battery charging of 3 kW gives grid export of 1 kW.
The solar panels are generating 6 kW. But only 1 kW is actually crossing the grid connection.
Solar generation tells you what the panels are producing. Export tells you what is left afterwards.
kW vs kWh for Solar Export
- Export Power — kW
- How quickly electricity is leaving the property at that moment.
- Exported Energy — kWh
- How much electricity has been exported over a period of time.
Solar export can be described using both kW and kWh. They mean different things.
For example, 5 kW of export for 2 hours equals 10 kWh exported.
kW tells you the export rate. kWh tells you the amount exported.
Where Can Surplus Solar Go?
Surplus electricity can have several possible destinations.
A simplified flow might be:
Solar → Home → Battery → EV → Hot Water → Grid
But that does not mean this should always be the fixed priority.
The best destination can depend on:
- tariff prices
- battery state of charge
- EV charging requirement
- hot-water demand
- household demand later
- backup reserve
- export value
Export is one possible destination for surplus solar, not simply the place electricity goes when everything else has failed.
Exported Solar Is Not Automatically Wasted
Solar export is often described as wasted solar.
That is not necessarily true.
If exported electricity earns a useful payment, then it still has financial value.
A homeowner may therefore be better off exporting some electricity rather than forcing every possible kWh into battery storage, hot water, EV charging or another discretionary load.
The correct decision depends on what the electricity is worth in each destination.
Exported solar is not wasted solar if the grid is paying enough for it.
The Best Destination Can Change Through the Day
- Morning
- Solar may be best used directly by the home.
- Midday
- The battery may charge while additional surplus exports.
- Afternoon
- An EV may be available to absorb solar.
- Evening
- Energy stored earlier may be more valuable because grid electricity is expensive.
There is no single destination that is always best.
The best place for a solar kWh is not always the same place at every time of day.
Should You Store Solar or Export It?
This is one of the most important questions in a modern solar and battery system.
The answer depends on the value of the electricity.
Consider:
- export tariff
- future import tariff
- battery round-trip efficiency
- battery state of charge
- expected household demand
A battery should not automatically receive every surplus kWh simply because there is spare capacity.
A battery should compete with export on value, not automatically replace it.
Worked Example: Store or Export?
Example
Export rate: 15p/kWh. Later import rate: 30p/kWh. Battery round-trip efficiency: 90%.
If you export 1 kWh you receive 15p.
If you store 1 kWh and around 0.9 kWh returns later, the avoided import value is approximately 0.9 × 30p = 27p.
In this simplified example, storing the energy is more valuable.
But change the tariff — export rate 25p, later import rate 20p — and now exporting can be more attractive.
Compare what 1 kWh is worth exported now with what the smaller recovered amount is worth later.
Battery Efficiency Changes the Store-or-Export Decision
A battery does not return every kWh that enters it.
Some energy is lost during charging, conversion, storage and discharge.
That means 1 kWh stored may return less than 1 kWh to the home later.
So storing electricity should be assessed against the value of exporting it immediately.
Battery storage changes when solar is used, but it also loses a small amount of energy along the way.
High Solar Self-Consumption Is Not Automatically Best
A monitoring app might show 95% solar self-consumption and make that look like the perfect result.
But a high self-consumption percentage does not tell you whether the system made the best financial decisions.
You could increase self-consumption by:
- storing energy when export is more valuable
- heating water unnecessarily
- charging an EV when cheaper electricity is available later
- deliberately creating demand
That can make the self-consumption percentage look better while reducing overall value.
High self-consumption is not automatically the same as high financial value.
Solar Self-Consumption vs Self-Sufficiency
- Solar Self-Consumption
- The percentage of generated solar electricity used within the property.
- Solar Self-Sufficiency
- The percentage of the property's electricity demand supplied by solar.
These two terms are often confused. They answer different questions.
A home can have high self-consumption but modest self-sufficiency, or high self-sufficiency but significant export.
Both figures can be useful, but they should not be treated as the same measurement.
What Is the Smart Export Guarantee?
The Smart Export Guarantee, usually shortened to SEG, is the UK framework under which eligible small-scale generators can be paid for electricity exported to the grid.
Export arrangements normally depend on:
- suitable metering
- supplier eligibility rules
- tariff terms
- system eligibility
Suppliers set their own export tariffs, so payment rates and conditions vary.
That means the important question is not simply how much do I export?
It is also what is each exported kWh worth?
The value of exported solar depends on the tariff, not simply on how many kWh leave the property.
Tied vs Untied Export Tariffs
- Untied Export Tariff
- May allow more freedom around electricity import supplier, battery brand and equipment choice.
- Tied Export Tariff
- May require conditions such as using the same supplier for import, being on a particular tariff, owning particular equipment, or allowing some battery control.
Export tariffs can operate in different ways.
That means the tariff with the highest headline export rate is not automatically the best choice.
The highest export rate is not always the most flexible export tariff.
The Headline Export Rate Is Not the Whole Tariff
When comparing export tariffs, also check:
- eligibility
- import tariff conditions
- whether batteries are allowed
- whether deliberate battery export is allowed
- whether supplier control is required
- time-of-use rates
- contract terms
- tariff duration
A high export payment can still influence the rest of the home’s energy strategy.
A high export rate can come with conditions that change how the rest of the energy system should behave.
Flat vs Time-Sensitive Export Tariffs
Some tariffs pay a similar export rate throughout the day.
Others may reward export differently depending on time, grid demand or tariff window.
This means 1 kWh exported at midday may not always have the same value as 1 kWh exported later.
That becomes especially important when battery storage is involved.
Not every exported kWh has the same value.
Natural Solar Export vs Deliberate Battery Export
- Natural Solar Export
- Solar generation exceeds what the home and battery need, so surplus flows directly to the grid.
- Deliberate Battery Export
- Stored electricity is intentionally discharged from the battery and sent to the grid.
The same meter may record both as export. But the energy strategy is very different.
Battery export can also interact with tariff rules, battery warranty, DNO export limits and battery efficiency.
Solar export and battery export can cross the same meter but represent different energy strategies.
Supplier-Controlled Battery Export
Some energy tariffs can interact directly with home battery systems.
The supplier or energy-management platform may influence when the battery charges, when it holds energy, when it discharges and when electricity is exported.
That can be useful if the system is being optimised around grid conditions or tariff prices.
But the homeowner should understand:
- who controls the battery
- when control can occur
- what reserve remains available
- how the tariff works
- whether warranty conditions are affected
Choosing an export tariff can sometimes also mean choosing how much control the supplier has over the battery.
What Is a Solar Export Limit?
A solar export limit controls the maximum net power that the property is allowed to send into the grid.
For example, a solar and battery system capability of 10 kW with permitted export of 5 kW.
The property may be capable of moving more power internally. But the system must prevent more than the agreed export power from flowing into the network.
The inverter may be capable of more power than the property is allowed to export.
Export Limit Is Not the Same as Solar Generation Limit
This distinction is very important.
Imagine solar generation of 8 kW, home demand of 2 kW, battery charging of 1 kW and export of 5 kW.
The property is generating 8 kW while exporting only 5 kW. The other 3 kW is being used inside the property.
An export limit controls what crosses the meter, not necessarily what the solar array can generate.
How Dynamic Export Limiting Works
A modern export-control system can continuously monitor the electricity flowing through the grid connection.
A simplified control path is:
Solar + Battery + Home Demand → Metering → Export Controller → Inverter
If net export starts to approach the agreed limit, the system can adjust power flows to keep export within that boundary.
This is why export-limited systems may use CT clamps, energy meters, gateways and inverter controls.
The system is responding to what the whole property is doing, not simply limiting the solar panels to one fixed number.
Inverter Size vs Export Limit
Several different power figures can exist in the same solar installation:
- solar array size
- inverter rating
- battery inverter power
- export limit
They do not need to be identical.
A solar system can therefore have larger generation capability than its permitted export.
The design depends on how much electricity can also be used onsite, stored or controlled.
A Battery Can Help with an Export Limit
Example
Solar generation 8 kW, home demand 1 kW, export limit 5 kW.
Without a battery, potential export would be 7 kW — above the export limit.
Now add battery charging at 2 kW. The energy can be distributed as home 1 kW, battery 2 kW, grid export 5 kW. Total solar used: 8 kW.
No solar needs to be curtailed in that moment.
A battery can turn an export constraint into stored energy, provided it has enough spare capacity and charge power.
What Happens When the Battery Is Full?
Use the same example: solar potential 8 kW, home demand 1 kW, export limit 5 kW, battery full.
Now only 1 kW home + 5 kW grid export = 6 kW has somewhere to go.
If the array could produce 8 kW, the system may need to reduce generation by approximately 2 kW at that moment.
Once the battery is full, an export limit can become a generation limit in practice.
Battery Charge Power Matters Too
A battery does not only need empty capacity. It also needs enough charge power to absorb surplus generation quickly enough.
Imagine excess solar above home demand and export limit of 4 kW with a battery charge limit of 2 kW.
The battery may still have plenty of empty capacity, but only 2 kW can enter it at that moment. The remaining generation may need to be curtailed.
What Is Solar Curtailment?
Solar curtailment is available generation that is deliberately held back because the system has nowhere useful or permitted to send it.
This might happen because:
- export limit has been reached
- battery is full
- battery cannot charge quickly enough
- household demand is low
- another system constraint has been reached
Solar curtailment is available generation that is deliberately held back because the system has nowhere useful or permitted to send it.
Curtailment Is Not Automatically a Fault
If an inverter reduces its output to prevent the property exceeding an agreed export limit, it may be operating exactly as designed.
The important question is not simply did the inverter reduce output?
It is why did it reduce output, and how much annual energy was actually affected?
A system reducing output to stay inside an export limit may be operating exactly as designed.
Look at Annual Curtailment, Not One Sunny Moment
Imagine an inverter reduces available solar output by 2 kW for a brief period on a clear summer afternoon.
That can look dramatic on a live monitoring graph.
But the more useful questions are:
- how often does it happen?
- for how long?
- which months?
- how many kWh are lost across the year?
A short power restriction can represent a much smaller annual energy loss.
A large instantaneous curtailment figure can represent a much smaller annual energy loss than it first appears.
Solar Direction Changes the Export Profile
Solar orientation affects more than annual generation.
A south-facing array can produce a stronger midday peak. East- and west-facing panels can spread generation over a wider part of the day.
That can change direct solar use, battery charging, peak export power, curtailment and export timing.
Solar layout changes when energy is exported, not just how much is generated across the year.
Large Solar Arrays Can Still Work with Lower Export Limits
A solar array does not necessarily need to have the same rating as the permitted export limit.
A larger array may still be useful because:
- the home uses some generation directly
- the battery stores some
- east/west orientation spreads production
- winter output improves
- only occasional summer peaks are curtailed
The important measure is the whole-year result.
Solar array size and export limit should be assessed together, but they do not have to be identical.
Inverter Clipping vs Export Curtailment
- Inverter Clipping
- Available solar DC power exceeds what the inverter can convert.
- Export Curtailment
- The system reduces output because more generation would exceed the permitted net export limit.
Both can reduce peak power. But they happen for different reasons.
Clipping and export curtailment can both reduce peak output, but for different reasons.
A Solar Panel Does Not Need to Match Household Demand Perfectly
Solar is sometimes assessed as though electricity only has value when it is used immediately inside the home.
Export changes that.
A panel generating while household demand is low can still create value if that electricity can be sold.
That means the value of east-facing panels, west-facing panels and additional roof areas should not be assessed only against instantaneous household demand.
A solar panel does not have to generate at the exact time the home needs electricity to create value.
Export Can Improve the Case for Additional Roof Areas
Imagine scaffolding, inverter capacity and electrical infrastructure are already part of the installation.
Adding panels to another usable roof face may have a relatively modest additional cost.
Even if some of that generation is exported, it can still add value.
The correct question is not will every additional kWh be used in the home?
It is is the additional generation worth more than the additional cost of installing it?
Charging an EV from Surplus Solar
An EV can absorb significant amounts of solar electricity where:
- the vehicle is at home
- the charger supports solar-aware charging
- enough surplus is available
- charging timing works for the homeowner
But avoiding export should not become the only objective.
If the EV can buy very cheap electricity overnight, it may sometimes be financially better to export daytime solar and charge the vehicle later.
Using solar onsite is only valuable if it creates more value than the export you give up.
Using Surplus Solar for Hot Water
Solar diverters can send surplus electricity to an immersion heater.
That can be useful.
But again, the correct comparison is financial.
If the electricity could instead earn a useful export payment, replace hot water produced efficiently by a heat pump, or be stored for a more valuable period, then immersion diversion may not always be the best destination.
Using solar onsite is only valuable if the electricity replaces something worth more than the export you give up.
Do Not Create Low-Value Demand Just to Avoid Export
A solar system should not deliberately create unnecessary energy consumption just to increase self-consumption.
Examples might include:
- heating water that is already hot
- forcing a heat pump to operate at an inefficient time
- charging an EV when cheaper charging is available later
- charging a battery when export is more valuable
Do not create low-value demand merely to avoid export.
Where Should the Next Surplus kWh Go?
As home-energy systems become more intelligent, the real question becomes:
Where should the next surplus kWh go?
Possible destinations include:
- immediate home demand
- battery
- EV
- hot water
- grid export
But even that order should not always be fixed.
It can change with tariff, battery SOC, weather forecast, EV departure time, backup reserve and future electricity price.
The correct export strategy is a priority decision, not a fixed rule.
Design for Flexible Energy Flows, Not One Tariff
Solar panels can operate for decades. Export tariffs can change much sooner.
That means a good solar design should not depend completely on one particularly attractive tariff remaining available forever.
A flexible system can adapt between direct use, storage, EV charging, hot water and export as energy prices and household needs change.
Design the system around flexible energy flows, not one export tariff that may change long before the panels do.
Historical Export Data Is Extremely Valuable
If the property already has solar, real export data can make future decisions much easier.
Useful information can include annual export, monthly export, half-hourly export, peak export and seasonal profile.
This is particularly useful when considering a battery.
Instead of estimating how much surplus might be available, you can see how the system actually behaves.
Existing solar gives you real evidence of how much electricity is available to store — and when it is available.
Export Data Should Be Read Alongside Import Data
Suppose a property exports 2,000 kWh/year and imports 2,000 kWh/year.
It is tempting to think a battery could eliminate the imports.
But timing matters.
The export may happen during sunny summer afternoons while imports occur on dark winter evenings.
A battery cannot seasonally move summer energy into winter.
The useful question is: can exported electricity be shifted into periods where it replaces sufficiently valuable imports?
Solar Export Is Highly Seasonal
- Summer
- Higher solar generation, longer days, potentially more export.
- Winter
- Lower solar generation, higher household demand, potentially little export.
That is why a battery should not be sized from one perfect summer day.
Solar export is seasonal, so storage decisions should be based on a year of behaviour rather than one perfect summer day.
Smart Export Guarantee vs Legacy Feed-in Tariff
The Smart Export Guarantee and the older Feed-in Tariff system are different arrangements.
Modern SEG payments are based around eligible exported electricity and suitable metering.
Older FiT installations may have generation payments, deemed export arrangements, separate export metering or different contractual rules.
Homeowners with older systems should understand their existing arrangement before changing how export is measured or controlled.
SEG and legacy Feed-in Tariff arrangements should not be treated as the same thing.
Be Careful Before Changing an Older FiT System
Important
Adding a battery, export metering, new inverter equipment or different export arrangements to an older FiT installation may require additional checks.
Do not assume that modern SEG advice applies directly to a legacy system.
If the solar installation receives legacy FiT payments, understand the existing metering and export arrangement before changing how energy is stored or exported.
What Should a Good Solar Proposal Show?
A good solar proposal should explain more than the total annual generation figure.
It should ideally show:
- estimated annual solar generation
- estimated direct household use
- estimated battery storage where relevant
- estimated annual export
- expected export limit
- material curtailment assumptions
- battery assumptions
- tariff assumptions
- where generated electricity is expected to go
A solar proposal should explain not only how much electricity the panels generate, but what happens to that electricity afterwards.
Worked Example: Generation vs Export
Example
Solar generation 6 kW, home demand 2 kW, battery charging 3 kW, export 1 kW.
The solar system is generating 6 kW but only 1 kW is being exported.
Generation is not export.
Worked Example: Export-Limited Solar with a Battery
Example
Solar generation 8 kW, home demand 1 kW, battery charging 2 kW, export limit 5 kW.
Energy flows: home 1 kW, battery 2 kW, grid 5 kW. Total 8 kW. All available solar has somewhere to go.
Now imagine the battery reaches 100%. Only 1 kW home + 5 kW export = 6 kW can now be accommodated. The system may need to curtail around 2 kW of available solar at that moment.
A battery can delay export curtailment, but it does not remove the export limit.
Common Solar Export Questions
What is solar export?
Solar export is surplus electricity that flows from the property into the grid when generation exceeds onsite use and storage.
Is exported solar wasted?
No. Exported electricity can have financial value through an export tariff.
What is the difference between solar generation and export?
Generation is the total electricity produced by the solar system. Export is the amount left after onsite electricity use and storage.
What is the Smart Export Guarantee?
SEG is the UK framework through which eligible small-scale generators can receive payment for electricity exported to the grid.
Do I need a smart meter to be paid for export?
Export payments require suitable metering capable of recording exported electricity. The precise meter and tariff requirements should be checked with the chosen supplier.
What is a tied export tariff?
A tied export tariff may require other conditions, such as using the same supplier for imported electricity, being on a specific tariff or using particular equipment.
Should I store solar or export it?
Compare the export payment with the value of the energy returned from the battery later after storage losses.
Does a battery always reduce solar export?
Usually it can reduce export while charging, but export can continue if the battery is full, charge-power limited or being controlled for another strategy.
Why am I exporting when my battery is not full?
The battery may be limited by charge power, operating settings, temperature or control strategy.
What is a solar export limit?
It is the maximum net electrical power the property is permitted or configured to send into the grid.
Is the export limit the same as inverter size?
No. The inverter may be capable of more power than the property is allowed to export.
Can solar generate more than the export limit?
Yes. Electricity can be used by the home or battery while net export remains below the limit.
What is solar curtailment?
Curtailment is available solar generation that is deliberately reduced because the system has nowhere useful or permitted to send it.
Why does my inverter reduce output on a sunny day?
Possible reasons include inverter clipping, battery limits or export curtailment. They are different system behaviours.
Can a battery help with an export limit?
Yes. A battery can absorb solar that would otherwise exceed the export limit, provided it has spare capacity and enough charge power.
What happens when the battery becomes full?
If household demand is low and the export limit has been reached, available solar generation may need to be curtailed.
Is high solar self-consumption always better?
No. Financial value depends on what exported electricity is worth compared with using or storing it.
What is the difference between solar self-consumption and self-sufficiency?
Self-consumption measures how much generated solar is used onsite. Self-sufficiency measures how much household demand is covered by solar.
Can I deliberately export electricity from a home battery?
Some systems and tariffs allow this, subject to equipment, supplier, warranty and DNO conditions.
Can I export more by adding a larger inverter?
Not necessarily. The site’s permitted export limit may remain unchanged.
Should solar export affect battery size?
Yes, but annual export alone should not determine battery capacity. Timing, tariff value and seasonal behaviour matter.
Should I use surplus solar to heat hot water rather than export it?
Only if the value of the avoided hot-water energy is greater than the export value you give up.
How does solar direction affect export?
Different orientations change the timing and peak power of solar generation, which can change the export profile.
Does adding more solar panels always increase export?
Not necessarily. Extra generation may instead increase direct use, battery charging or curtailment depending on the system.
Are SEG and FiT the same?
No. SEG is the current export-payment framework, while legacy Feed-in Tariff installations can have different generation and export arrangements.
Give Every Surplus kWh a Purpose
A good solar system does not simply try to avoid export.
It decides where surplus electricity creates the most value.
That may mean using it directly, storing it, charging an EV, heating water or exporting it.
The best choice can change with the tariff, battery state, household demand and time of day.
Solar export is what remains after the home, battery and other controllable loads have taken what they can use.
Exported solar is not wasted solar if the grid is paying enough for it.
The aim is not to eliminate export. It is to decide which surplus kWh are worth storing, using or selling.
An export limit controls what crosses the meter, not necessarily what the solar array can generate.
Once the battery is full, an export limit can become a generation limit in practice.
High self-consumption is not automatically the same as high financial value.
Export is part of the system architecture, not just the final line on the electricity bill.