Export limitation is a setting in your solar inverter that caps how much power can be sent to the electricity grid. By limiting export to 3.68 kW, you can install a larger solar system (5 kW, 6 kW, or more) while staying within the G98 notification threshold, avoiding the lengthy G99 application process that can delay installation by months.
The trade-off is curtailment – when your system generates more power than you’re using plus the export limit, the excess is wasted rather than exported. However, for many UK households, especially those with batteries or good daytime usage, the amount curtailed is surprisingly small, making export limitation an attractive option for faster installation and larger system capacity.
This guide explains how export limitation works, when it makes financial sense, how much energy you might lose, and how to decide whether to export limit or pursue full G99 approval.
Quick Overview
| What it does | Caps power sent to grid |
| Common limit | 3.68 kW (G98 threshold) |
| Main benefit | Avoid G99 application delays |
| Trade-off | Some generation may be curtailed |
| Who it suits | Battery systems; high self-consumption |
| Typical curtailment | 2-10% of annual generation |
How Export Limitation Works
Basic Principle
| Component | Function |
|---|---|
| CT clamp | Measures power flow at meter |
| Inverter | Monitors export in real-time |
| Control system | Reduces output if limit reached |
| Response time | Milliseconds to seconds |
What Happens in Practice
| Scenario | System Behaviour |
|---|---|
| Generation 4 kW; using 2 kW | Export 2 kW – under limit; fine |
| Generation 5 kW; using 2 kW | Export 3 kW – under limit; fine |
| Generation 5 kW; using 1 kW | Would export 4 kW – limited to 3.68 kW |
| Generation 5 kW; using 0 | Would export 5 kW – limited to 3.68 kW |
Curtailment Explained
| Term | Meaning |
|---|---|
| Curtailment | Generation potential not used |
| When it occurs | Generation > consumption + export limit |
| What happens | Inverter reduces output |
| Energy lost | Not generated; not stored |
Why Export Limit?
G98 vs G99 Connection
| Aspect | G98 (≤3.68 kW) | G99 (>3.68 kW) |
|---|---|---|
| Process | Notification only | Formal application |
| Timeline | Immediate | 45-90+ working days |
| Approval needed | No | Yes |
| Risk of refusal | None | Possible |
| Cost | Free | Usually free; sometimes fees |
For the full picture of how each application path works in practice, see our DNO approval process guide and the more practical DNO solar application guide, which both cover what your installer needs to submit and the timeline for each route.
Benefits of Export Limiting
| Benefit | Details |
|---|---|
| Faster installation | No 2-4 month G99 wait |
| Guaranteed connection | G98 can’t be refused |
| Larger system possible | Install 5-6 kW+ capacity |
| More self-consumption | Bigger system; more direct use |
| Better winter output | Larger array generates more |
| Battery charging | Excess charges battery instead |
Avoiding Network Constraints
| Issue | Export Limiting Benefit |
|---|---|
| Constrained network | G99 might be refused anyway |
| Reinforcement costs | Avoided entirely |
| Rural areas | Often constrained; G98 safer |
| Many local solar | Network may be at capacity |
Common Export Limit Settings
Standard Limits
| Limit | Purpose |
|---|---|
| 3.68 kW | G98 threshold (most common) |
| 0 kW (zero export) | No power to grid at all |
| Custom limit | DNO-specified requirement |
| Dynamic/flexible | Varies with network conditions |
Single Phase vs Three Phase
| Supply | G98 Limit | Export Limit Setting |
|---|---|---|
| Single phase | 3.68 kW total | 3.68 kW |
| Three phase | 11.04 kW total | 3.68 kW per phase or 11.04 kW total |
DNOs publish official guidance on export limitation alongside their G99 application processes – SP Energy Networks’ export limitation page is a representative example, including a Fast Track G99 process for export-limited PV-plus-storage systems below the threshold per phase.
How Much Energy Is Curtailed?
Factors Affecting Curtailment
| Factor | Impact on Curtailment |
|---|---|
| System size | Larger = more potential curtailment |
| Household consumption | Higher use = less curtailment |
| Consumption timing | Daytime use = less curtailment |
| Battery storage | Absorbs excess = less curtailment |
| Location (irradiance) | Sunnier = more peak generation |
Typical Curtailment Levels
| System | Scenario | Annual Curtailment |
|---|---|---|
| 4 kW panels; 3.68 kW limit | No battery; low daytime use | 1-3% |
| 5 kW panels; 3.68 kW limit | No battery; low daytime use | 3-6% |
| 6 kW panels; 3.68 kW limit | No battery; low daytime use | 5-10% |
| 5 kW panels; 3.68 kW limit | With battery | 1-3% |
| 6 kW panels; 3.68 kW limit | With battery | 2-5% |
| Any size | High daytime consumption | Minimal |
When Curtailment Occurs
| Condition | Likelihood |
|---|---|
| Summer midday | Most likely – peak generation |
| Sunny weekend; nobody home | High – low consumption |
| Clear spring/autumn day | Moderate |
| Winter | Rare – lower generation |
| Cloudy days | Rare – below limit |
| Evenings/mornings | Rare – lower generation |
Financial Impact
Value of Curtailed Energy
| Calculation | Example |
|---|---|
| Annual generation | 5,000 kWh (5 kW system) |
| Curtailment at 5% | 250 kWh lost |
| Export rate (SEG) | ~15p/kWh |
| Annual loss | ~£37.50 |
Comparing G99 Delay Cost
| Factor | G99 Wait Cost |
|---|---|
| Delay period | 3 months typical |
| Lost generation (summer) | 1,200-1,500 kWh |
| Lost savings + export | £150-300 |
| Compared to curtailment | Often exceeds years of curtailment loss |
Break-Even Analysis
| Scenario | Years to Break Even |
|---|---|
| 3-month delay avoided; 5% curtailment | Immediate benefit |
| £200 delay cost avoided; £40/year curtailment | 5 years ahead |
| Summer installation delayed | Even greater benefit |
If you’re trying to estimate how much SEG income you’d actually earn at different export rates and limits, our SEG calculator works through the maths for typical UK system sizes.
Battery Systems and Export Limiting
Why Batteries Reduce Curtailment
| Mechanism | Effect |
|---|---|
| Absorbs excess | Battery charges instead of curtailing |
| Increases self-consumption | Less need to export anyway |
| Shifts usage | Evening use from stored solar |
| Buffer capacity | 5-10 kWh absorbs peak generation |
Example: 6 kW System With Battery
| Time | Generation | Consumption | Battery | Export | Curtailed |
|---|---|---|---|---|---|
| 10am | 4 kW | 0.5 kW | Charging 3.5 kW | 0 kW | 0 |
| 12pm | 5.5 kW | 0.5 kW | Full; stops | 3.68 kW | 1.32 kW |
| 2pm | 5 kW | 1 kW | Full | 3.68 kW | 0.32 kW |
| 4pm | 3 kW | 1 kW | Full | 2 kW | 0 |
Battery Sizing Consideration
| Battery Size | Curtailment Reduction |
|---|---|
| 5 kWh | Absorbs 2-3 hours of excess |
| 10 kWh | Absorbs most daily excess |
| 15 kWh+ | Rarely fills; minimal curtailment |
For sizing a battery to your specific generation pattern and tariff, see our best solar batteries guide. If you’re retrofitting a battery to existing solar, the curtailment savings often help offset the install cost over time.
Zero Export
What Is Zero Export?
| Aspect | Details |
|---|---|
| Setting | Export limit = 0 kW |
| Effect | No power ever sent to grid |
| Self-consumption | Must be 100% or curtailed |
| SEG income | None – nothing exported |
When Zero Export Required
| Situation | Why Required |
|---|---|
| DNO mandate | Network cannot accept any export |
| Specific connection | Terms of approval |
| Private wire | No grid connection for export |
| Commercial premises | Sometimes required |
Zero Export Impact
| System | Curtailment Without Battery |
|---|---|
| 4 kW system | 40-60% curtailed |
| With battery | 10-25% curtailed |
| High daytime use | 20-40% curtailed |
Technical Implementation
CT Clamp Installation
| Aspect | Details |
|---|---|
| Location | Around meter tails |
| What it measures | Import/export power flow |
| Connection | Wired to inverter |
| Essential for | Export limiting to work |
Inverter Settings
| Setting | Configuration |
|---|---|
| Export limit value | 3680W or 3.68 kW |
| CT clamp enabled | Must be on |
| Response speed | Fast enough to stay within limit |
| Fail-safe | Some stop entirely if CT fails |
Monitoring Curtailment
| Method | What It Shows |
|---|---|
| Inverter app | May show power limiting active |
| Generation vs potential | Compare to similar systems |
| Flat-top generation curve | Indicates limiting occurring |
| GivEnergy; Sungrow; etc. | Often show “export limit” active |
A flat top to the midday generation curve in your monitoring app is the unmistakable signature of export limiting in action – a well-built energy dashboard will show both available solar power and actual export, with the difference being the curtailed energy.
When Export Limiting Makes Sense
Ideal Candidates
| Situation | Why Good Fit |
|---|---|
| Battery system planned | Battery absorbs excess |
| High daytime use | Use before export anyway |
| EV charging at home | Large daytime load available |
| Home worker | Higher daytime consumption |
| Heat pump | Can run during solar hours |
| Want larger system | More capacity; faster install |
| Constrained network area | G99 might be refused |
Less Ideal Candidates
| Situation | Why Less Suited |
|---|---|
| No battery; no daytime use | Higher curtailment |
| Maximum export income priority | Every kWh matters |
| Very large system (10 kW+) | Significant curtailment |
| Time not a concern | G99 wait acceptable |
If you have an EV at home, scheduling charging during midday solar peaks turns potentially curtailed kWh into stored vehicle energy – see our solar panels for EV charging guide for the practicalities. Similarly, automating appliances around solar generation can absorb most of the would-be curtailment by running washing machines and water heating at the right time.
DNO-Mandated Export Limits
When DNO Requires Limits
| Situation | Details |
|---|---|
| G99 approval condition | Approved with limit |
| Constrained network | Network can’t take full output |
| Alternative to refusal | Accept limit or no connection |
| Flexible connection | Limit varies with conditions |
Flexible/Smart Export
| Type | How It Works |
|---|---|
| Time-based | Different limits at different times |
| ANM (Active Network Management) | DNO signals limit in real-time |
| Price-based | Future: export when valuable |
Comparing Options
5 kW System Decision
| Option | Pro | Con |
|---|---|---|
| 3.68 kW inverter | No limit needed; G98 | Smaller system; clips generation |
| 5 kW; export limited | Larger system; G98; fast | Some curtailment |
| 5 kW; G99 | No curtailment | Wait 2-4 months; possible refusal |
With Battery Comparison
| Option | Annual Curtailment | Timeline |
|---|---|---|
| 5 kW + battery; G98 limited | ~2% | Immediate |
| 5 kW + battery; G99 | 0% | 3+ months |
| Lost generation waiting | N/A | 1,000+ kWh |
Installation Considerations
What Installer Does
| Task | Details |
|---|---|
| Advise on approach | G98 limited vs G99 |
| Install CT clamp | Required for limiting |
| Configure inverter | Set export limit |
| Test function | Verify limiting works |
| Document settings | For DNO notification |
Questions to Ask Installer
| Question | Why Important |
|---|---|
| What’s curtailment estimate? | Understand impact |
| Can limit be changed later? | Flexibility for future |
| How will I see curtailment? | Monitoring capability |
| G99 option timeline? | Compare alternatives |
Changing Export Limit Later
Increasing Limit
| Situation | Process |
|---|---|
| Remove limit entirely | G99 application required |
| Increase within G98 | Up to 3.68 kW; just reconfigure |
| Three phase upgrade | Higher G98 limit (11.04 kW) |
Reducing Limit
| Situation | Process |
|---|---|
| DNO request | May be required |
| Voluntary | Simple setting change |
| Zero export | Possible if needed |
Real-World Examples
Example 1: Working From Home
| Detail | Value |
|---|---|
| System | 5.5 kW panels; 5 kW inverter |
| Export limit | 3.68 kW |
| Daytime consumption | 1-2 kW (computer; appliances) |
| Annual curtailment | ~3% (150 kWh) |
| Lost export value | ~£22/year |
| Verdict | Excellent choice |
Example 2: Family Home With Battery
| Detail | Value |
|---|---|
| System | 6 kW panels; 5 kW hybrid; 10 kWh battery |
| Export limit | 3.68 kW |
| Battery absorbs excess | Most days; fills by 2pm summer |
| Annual curtailment | ~4% (240 kWh) |
| Lost export value | ~£36/year |
| Avoided G99 delay | 3 months; ~£250 of generation |
| Verdict | Clear benefit |
Example 3: Holiday Home
| Detail | Value |
|---|---|
| System | 4 kW panels; 3.68 kW inverter |
| Export limit | Not needed – at threshold |
| Usage pattern | Empty most of time |
| Most generation exported | Maximise SEG |
| Verdict | Right-sized; no limit needed |
Frequently Asked Questions
Basic Questions
| Question | Answer |
|---|---|
| Does export limiting affect self-use? | No – full system for home use |
| Can I still get SEG payments? | Yes – for what you export |
| Is curtailment wasted energy? | Yes – not generated or stored |
| Can I remove the limit later? | Yes – but need G99 approval |
Technical Questions
| Question | Answer |
|---|---|
| What if CT clamp fails? | Depends on inverter; may stop export |
| Does DNO check the limit? | Declared; rarely inspected |
| Can I set limit slightly higher? | Must not exceed 3.68 kW for G98 |
| Does battery change the maths? | Yes – significantly reduces curtailment |
Summary
| Aspect | Key Point |
|---|---|
| What it is | Cap on power sent to grid |
| Common setting | 3.68 kW for G98 compliance |
| Main benefit | Avoid G99 delays; larger system |
| Typical curtailment | 2-10% without battery |
| With battery | 1-5% curtailment |
| Financial impact | Usually small; offset by faster install |
Export limitation lets you install a larger solar system while staying within the simple G98 notification process. By capping export to 3.68 kW, a 5 kW or 6 kW system can connect immediately without the 2-4 month wait (and potential refusal) of G99 approval. The trade-off is some curtailment – generation that’s reduced because it would exceed your export limit plus consumption.
For most households, especially those with battery storage or good daytime consumption, curtailment is surprisingly small. A typical 5 kW system with a battery might lose just 2-3% of annual generation to curtailment – perhaps £30-40 of export income per year. Compare this to the £150-300 of generation lost waiting for G99 approval, and export limiting often makes clear financial sense.
The decision depends on your circumstances. If you have a battery, work from home, charge an EV during the day, or run a heat pump, export limiting is usually the right choice. If you’re rarely home during the day, have no battery, and want to maximise export income from a smaller system, a right-sized 3.68 kW installation without limiting might be better.
Your installer can model the likely curtailment for your specific situation and help you decide. Either way, understanding export limitation helps you make an informed choice about system sizing and grid connection approach.
The decision usually comes down to two numbers. First, the curtailment estimate – what percentage of annual generation gets thrown away? For a typical 5 kW system with a battery this is 2-3%, costing £30-40/year at SEG rates. Second, the G99 wait cost – what generation would you lose during the 6-16 week approval window? In summer, this can be 1,000-1,500 kWh, worth £150-300. Almost always, the wait cost dominates – which is why export limiting is the default for any installation that wants to fire up quickly.
The exceptions: a holiday home or rental property where you’re rarely there to use solar directly, a very large system (10 kW+) where the curtailment percentage stays small but the absolute kWh number gets meaningful, and any situation where your installer flags a known network constraint that would force a limit anyway. In those cases, ask your installer to model both options against your actual usage pattern – the answer is rarely close.
