EV Charger Load Balancing: Complete UK Guide 2025

EV Charger Load Balancing: Complete UK Guide 2025

EV charger load balancing solves a critical challenge facing UK multi-EV households: how to charge 2-4 electric vehicles simultaneously without exceeding your home's electrical supply capacity or spending £3,000-£8,000 on costly consumer unit upgrades. With dynamic load management systems from brands like Easee, Zappi, and Wallbox, households can intelligently share available power across multiple chargers, automatically adjusting charging rates to prevent circuit overload while maximizing charging speed within safe limits.

The problem is acute: a typical UK home has 60-100A (13.8-23kW) total supply capacity. Running two standard 7.4kW chargers simultaneously demands 32A per charger (64A combined)—potentially exceeding capacity when combined with home loads like ovens, showers, and heat pumps. Load balancing systems monitor real-time electrical consumption and dynamically allocate power, preventing trips while ensuring both vehicles charge overnight.

This comprehensive guide explains EV charger load balancing technology, compatible systems for UK homes (Easee Equaliser, Zappi + Harvi, Wallbox multi-charger setups), installation costs (£1,400-£3,200 for two-charger systems), configuration requirements, and whether load balancing or electrical upgrades represent better value for multi-EV households in 2025.

Understanding Load Balancing: The Technical Challenge

Before exploring solutions, it's essential to understand why multi-EV households face electrical capacity constraints:

Typical UK Home Electrical Capacity:

Single-Phase Supply (Most Homes):

• Main Fuse Rating: 60A or 100A
• Maximum Power Available:
  • 60A × 230V = 13.8kW
  • 100A × 230V = 23kW
• Usable Capacity: Main fuse rating minus diversity allowance (safety margin)
• Realistic Available for EV Charging: 8-15kW after household loads

The Multi-EV Problem:

Scenario: Two EVs, Standard 7.4kW Chargers

Simultaneous Charging Demand:

• EV 1: 7.4kW (32A at 230V)
• EV 2: 7.4kW (32A at 230V)
• Total: 14.8kW (64A)

Household Base Load (Evening):

• Electric oven: 3kW (13A)
• Kettle: 2kW (8.7A)
• Heating/hot water: 3kW (13A)
• Lighting/appliances: 1kW (4.3A)
• Total Household: 9kW (39A)

Combined Load:

• Two EVs: 64A
• Household: 39A
• Peak Total: 103A

Problem: Exceeds 100A main fuse capacity—circuit breaker trips, power cut to entire home.

Traditional Solutions (Expensive):

Option 1: Consumer Unit Upgrade

• Install larger main fuse (if DNO permits)
• Upgrade incoming supply cables
• Cost: £2,000-£5,000
• Issue: DNO may refuse if local network at capacity

Option 2: Limit Charger Power

• Configure each charger to 3.6kW (16A)
• Two chargers: 32A combined (manageable)
• Cost: Free (software configuration)
• Issue: Charging takes twice as long (14 hours instead of 7 hours for 60kWh battery)

Modern Solution: Dynamic Load Balancing

How It Works:

1. Real-Time Monitoring: CT clamps measure total household power consumption
2. Available Capacity Calculation: System calculates spare capacity (e.g., 100A limit - 40A house load = 60A available)
3. Dynamic Allocation: Divides available power between chargers (e.g., 30A each = 6.9kW per charger)
4. Continuous Adjustment: As household loads change (oven turns off), system reallocates power to chargers

Result: Maximum safe charging speed at all times without manual intervention or circuit trips.

Load Balancing System Options (UK 2025)

Several manufacturers offer load balancing solutions suitable for UK residential installations:

Easee Equaliser System (Best Integrated Solution):

How It Works:

• Easee One Chargers: Install 2-3 Easee One chargers (£825-£975 each installed)
• Easee Equaliser: Central load balancing hub (included with multiple chargers)
• CT Clamp: Monitors main supply current
• Mesh Network: Chargers communicate wirelessly, sharing power allocation

Key Features:

• Automatic Discovery: Chargers detect each other automatically (no complex configuration)
• Dynamic Power Sharing: Allocates power based on vehicle needs and available capacity
• Built-in 4G: Cloud connectivity for remote monitoring
• Prioritization: Set priority vehicles (e.g., car 1 charges first)
• Smallest Footprint: 17cm diameter (UK's most compact charger)

Configuration Example: 100A Supply, Two Easee Chargers

• Main Supply: 100A (23kW)
• Household Base Load: 30A (6.9kW)
• Available for EVs: 70A (16.1kW)
• Easee Equaliser Allocation:
  • If one vehicle connected: 32A (7.4kW) to that vehicle
  • If two vehicles connected: 35A each (8kW each—dynamically shared)
  • If household load spikes to 50A: Reduces EV charging to 25A each (5.75kW)

UK Pricing (2-Charger System):

• 2× Easee One Chargers: £1,650-£1,950 (installed)
• Equaliser (included)
• CT Clamp Installation: £200-£300
• Total: £1,850-£2,250

Best For: New multi-charger installations, Scandinavian build quality, effortless setup

myenergi Zappi + Harvi System:

How It Works:

• Zappi Chargers: Install 2-3 Zappi units (£1,050-£1,250 each)
• Harvi Wireless Sensor: CT clamp with wireless transmitter monitors mains supply
• myenergi Hub (optional): Centralized control for multiple devices
• Power Allocation: Zappi units communicate, share available power

Key Features:

• ECO Mode Load Balancing: Allocates power while prioritizing solar excess
• myenergi Ecosystem: Integrates with eddi (immersion heater), libbi (battery storage)
• British Design: UK company, strong local support
• Solar Integration: Best-in-class solar diversion capabilities

Configuration Example: 100A Supply, Two Zappi Chargers

• Main Supply: 100A
• Household Load: 35A
• Available: 65A
• Zappi Allocation:
  • Primary Zappi: 32A (7.4kW)
  • Secondary Zappi: 33A (7.6kW)
  • Dynamic reallocation as household loads change

UK Pricing (2-Charger System):

• 2× Zappi Chargers: £2,100-£2,500
• Harvi Wireless CT: £100-£150
• Installation: £300-£400
• Total: £2,500-£3,050

Best For: Existing Zappi users, solar panel integration, myenergi ecosystem

Wallbox Pulsar Plus Multi-Charger (App-Based Load Management):

How It Works:

• Wallbox Pulsar Plus Chargers: Install 2-4 units
• Power Sharing Mode: Configured via app
• Static Allocation: Pre-set power limits (e.g., 16A per charger)
• Or Dynamic (Limited): Can adjust based on total capacity setting

Key Features:

• Affordable: Lowest per-charger cost
• WiFi/Bluetooth: App-based control
• Compact Design: Sleek appearance
• Smart Charging: Tariff integration

Limitation: Less sophisticated load balancing than Easee/Zappi (more manual configuration)

UK Pricing (2-Charger System):

• 2× Wallbox Pulsar Plus: £1,300-£1,600
• Installation: £500-£700
• Total: £1,800-£2,300

Best For: Budget-conscious multi-EV homes, manual control acceptable

Sync EV Multi-Charger Solution:

How It Works:

• Sync EV Chargers: British-designed chargers with built-in load balancing
• Master/Slave Configuration: One charger acts as master, controls others
• CT Clamp Monitoring: Monitors available capacity

UK Pricing (2-Charger System):

• 2× Sync EV Chargers: £1,600-£2,000
• Installation: £400-£600
• Total: £2,000-£2,600

Best For: British brand preference, straightforward master/slave setup

Installation Requirements and Process

Pre-Installation Assessment:

Step 1: Confirm Main Fuse Rating

Check your main fuse (before meter, sealed by DNO):

• Look for markings: "60A" or "100A"
• If unclear, contact DNO or electrician for assessment
• Take photo for electrician quote

Step 2: Calculate Available Capacity

Method A: Simple Assessment

• 100A supply: Can support 2× full-speed chargers (7.4kW) with load balancing
• 60A supply: Requires load balancing for 2 chargers, or limit to 3.6kW each

Method B: Detailed Load Calculation

Electrician performs load assessment:

1. Measure peak household consumption (evening)
2. Calculate diversity (not all loads run simultaneously)
3. Determine safe available capacity for EV charging
4. Configure load balancing limits accordingly

Step 3: Charger Location Planning

Ideal Setup:

• Both chargers near each other (simplifies electrical installation)
• Close to consumer unit (reduces cable runs)
• Adequate parking space for both vehicles

Less Ideal but Workable:

• Chargers at opposite ends of property (e.g., front drive + garage rear)
• Requires longer cable runs, potentially more installation cost
• Wireless load balancing systems (Easee, Zappi + Harvi) handle this well

Installation Process:

Week 0-1: Survey and Quote

1. MCS-certified electrician site visit
2. Assess consumer unit, main supply, charger locations
3. Verify load balancing system compatibility
4. Provide detailed quote (£1,400-£3,200 typical)

Week 2-3: Order Equipment

1. Order chargers (lead times: 2-4 weeks)
2. Order CT clamps and load balancing accessories
3. Schedule installation date

Week 4: Installation (1-2 Days)

Day 1 (Full Day):

1. Isolate Mains Supply
2. Install Consumer Unit Circuits:
   • Dedicated 32A circuit for each charger
   • RCD/RCBO protection per circuit
   • Cable runs to charger locations (6mm² cable typical)
3. Mount Chargers:
   • Wall mounting or post installation
   • Charger 1 and Charger 2 positioning
4. Install CT Clamps:
   • Main supply CT clamp (measures total household current)
   • Wired or wireless connection to chargers
5. Electrical Connections:
   • Connect each charger to dedicated circuit
   • Earth bonding
   • Testing (insulation resistance, earth loop impedance)

Day 2 (Half Day):

1. Configure Load Balancing:
   • Set main supply limit (e.g., 100A)
   • Configure household base load allowance (e.g., 30A)
   • Set charger priorities if required
   • Test dynamic allocation with vehicles connected
2. Commission System:
   • Plug in both vehicles
   • Verify load balancing active (check app/display)
   • Test household load changes (turn on oven, observe charger adjustment)
   • Handover and user training
3. Certification:
   • Issue electrical installation certificates (BS 7671)
   • MCS registration if applicable

Total Timeline: 4-5 weeks from survey to operation

Load Balancing vs Electrical Upgrade: Cost Comparison

Scenario: Two-EV Household, 60A Main Supply

Option 1: Load Balancing System

• 2× Easee One Chargers + Equaliser: £2,000
• Installation (2 circuits, CT clamp): £600
• Total: £2,600

Charging Capability:

• Both EVs charge overnight (8 hours)
• Dynamic sharing: 6-7kW per vehicle (adjusted based on household load)
• Typical overnight charge: 50-55 kWh per vehicle (sufficient for 170-190 miles)

Option 2: Electrical Supply Upgrade

• DNO Connection Upgrade (60A → 100A): £1,500-£3,000
• Consumer Unit Replacement: £800-£1,200
• 2× Standard Chargers: £1,400-£1,800
• Installation: £600-£900
• Total: £4,300-£6,900

Charging Capability:

• Both EVs charge at full 7.4kW (no power sharing)
• Faster charging (7 hours for 60 kWh)
• More future capacity for additional loads

Verdict: Load balancing saves £1,700-£4,300 compared to electrical upgrades and delivers adequate charging for most households. Upgrade only makes sense if you also need capacity for other high-power loads (heat pump, workshop equipment).

Real-World Multi-EV Household Scenarios

Scenario 1: Couple with Two EVs (60kWh Batteries Each)

Setup:

• Main Supply: 100A
• Household Load: 25-35A (evening)
• 2× Easee One Chargers with Equaliser
• Both vehicles plugged in 10pm-6am (8 hours)

Typical Overnight Operation:

• 10:00pm: Both vehicles arrive home (30% battery each, need 42 kWh each)
• 10:00pm-11:00pm: High household load (cooking, TV, shower)
  • Available for EVs: 50A (11.5kW shared)
  • Allocation: 5.75kW per vehicle
• 11:00pm-7:00am: Low household load (sleeping)
  • Available for EVs: 75A (17.25kW shared)
  • Allocation: 8.6kW per vehicle (maximum safe rate)
• By 7:00am: Both vehicles 95%+ charged

Result: Seamless overnight charging without manual intervention or circuit overload.

Scenario 2: Family with Three EVs (Mixed Battery Sizes)

Setup:

• Main Supply: 100A
• Vehicles:
  • EV 1: 75 kWh (Tesla Model Y)
  • EV 2: 60 kWh (VW ID.3)
  • EV 3: 40 kWh (Nissan Leaf)
• 3× Zappi Chargers with Harvi CT

Load Balancing Strategy:

Priority Configuration:

1. EV 1 (Tesla): Priority 1 (longest charge time needed)
2. EV 2 (VW): Priority 2
3. EV 3 (Leaf): Priority 3 (smallest battery, fastest charge)

Overnight Operation:

• 10pm-12am: EV 1 gets maximum available power (7.4kW), EV 2 gets remainder (6kW), EV 3 waits
• 12am-2am: EV 1 complete, power shifts to EV 2 (7.4kW) and EV 3 starts (6kW)
• 2am-5am: EV 2 complete, EV 3 gets full power (7.4kW)
• By 6am: All three vehicles fully charged

Result: Intelligent sequential/parallel charging ensures all vehicles ready by morning without exceeding capacity.

Scenario 3: High-Mileage Household (Two Company Cars)

Setup:

• Main Supply: 60A (older property)
• Both vehicles: 200+ miles daily use
• 2× Wallbox Pulsar Plus (configured to 16A each = 3.6kW)

Challenge: 60A supply limits total EV charging to ~10kW

Solution:

• Static Load Limit: 16A per charger (safe within 60A supply)
• Extended Charging Window: Plug in 6pm, charge until 7am (13 hours)
• Capacity: 3.6kW × 13 hours = 46.8 kWh per vehicle overnight
• Range: 46.8 kWh = ~165 miles per vehicle

If Insufficient:

• Top-up charge during lunch (home workers)
• Weekend daytime charging to 100%
• Consider DNO supply upgrade (long-term solution)

Result: Load balancing makes multi-EV viable even on constrained 60A supplies through extended charging periods.

Frequently Asked Questions

Q1: Can I charge two EVs at the same time in a UK home without load balancing? A: It depends on your main fuse rating and household load. A 100A supply can typically support two 7.4kW chargers if household consumption is low (<30A), but you risk circuit trips during high-demand periods (cooking, heating). A 60A supply cannot safely support two simultaneous 7.4kW chargers without load balancing—you'd need to limit each charger to 3.6kW or install load balancing.

Q2: How does load balancing affect charging speed? A: Load balancing slightly reduces individual charging speeds during simultaneous charging, but maximizes combined throughput. Example: Without load balancing, you might charge one car at 7.4kW while the other waits. With load balancing, both charge at 5-6kW simultaneously, completing in similar total time. Overnight (8+ hours), most households find load-balanced speeds adequate to fully charge both vehicles.

Q3: What happens if my household uses a lot of power while both EVs are charging? A: The load balancing system automatically reduces EV charging rates to prevent exceeding your main supply capacity. For example, if you turn on your oven (3kW) and both chargers are running, the system detects the 13A increase and reduces each charger's power by 6-7A to compensate. Charging continues, just slower temporarily. When the oven turns off, full power returns to the chargers.

Q4: Which load balancing system is best for UK homes—Easee, Zappi, or Wallbox? A: Easee Equaliser offers the most seamless experience (automatic charger discovery, true dynamic balancing, £1,850-£2,250 for two chargers). Zappi + Harvi is best if you have solar panels or want myenergi ecosystem integration (£2,500-£3,050 for two chargers). Wallbox Pulsar Plus is the budget option with more manual configuration (£1,800-£2,300). All three work effectively; choose based on budget and features.

Q5: Can I add a third EV charger to an existing load balancing system later? A: Yes, most systems (Easee, Zappi, Wallbox) support adding additional chargers. Easee is particularly straightforward—new chargers automatically join the mesh network. Zappi requires adding another unit and reconfiguring via the app. Ensure your electrician designs the initial installation with expansion in mind (adequate consumer unit capacity, spare RCD/RCBO slots).

Q6: Does load balancing work with three-phase electricity? A: Yes, load balancing systems support both single-phase (most UK homes) and three-phase supplies. Three-phase actually makes load balancing easier—you can dedicate one phase per charger and balance loads across phases. However, three-phase residential supplies are rare in the UK; most multi-EV load balancing installations use single-phase.

Q7: Can I use load balancing with smart tariffs like Octopus Intelligent Go? A: Yes, load balancing is compatible with smart tariffs. The load balancing manages power distribution between chargers, while the smart tariff controls when charging occurs (e.g., 12:30am-5:30am cheap period). Both systems work together—load balancing ensures safe power allocation during the smart tariff's charging window. Easee, Zappi, and Wallbox all integrate with Octopus Intelligent.

Q8: What's the minimum main fuse size needed for load balancing two EV chargers? A: Technically, load balancing works with any main fuse size (even 60A), but practical charging speeds vary. With a 60A supply and typical 30A household load, you have 30A available for EVs (6.9kW shared = 3.45kW per charger). This charges 27 kWh overnight (8 hours), sufficient for ~95 miles per vehicle. For comfortable two-EV charging, 80A+ supply is ideal, providing 5-6kW per vehicle.

Q9: Does load balancing increase my electricity bill? A: No, load balancing doesn't consume additional electricity—it's purely a power management system. Your electricity bill depends only on how much energy your vehicles consume (kWh), not whether you use load balancing. Load balancing may actually reduce costs by enabling you to use cheaper overnight tariffs (Octopus Intelligent Go, 7.5p/kWh) for both vehicles simultaneously.

Q10: Can I install load balancing myself or do I need a professional electrician? A: You must use a qualified electrician (ideally MCS-certified) for EV charger installations in the UK. Load balancing systems require:

• Consumer unit modifications (adding dedicated circuits)
• CT clamp installation on main supply (requires working near live mains)
• Electrical certification (BS 7671 compliance)
• DNO notification DIY installation is illegal for mains electrical work and voids insurance. Expect to pay £1,400-£3,200 for professional two-charger installation with load balancing.

Conclusion: Load Balancing Essential for Multi-EV UK Homes

For UK households with two or more electric vehicles, load balancing technology has evolved from optional luxury to practical necessity. Dynamic load management systems from Easee, Zappi, and Wallbox enable simultaneous multi-EV charging within existing electrical infrastructure, eliminating the need for costly £3,000-£8,000 supply upgrades while delivering adequate overnight charging speeds for typical daily mileage needs.

The investment is modest—£1,850-£3,050 for a complete two-charger system with intelligent power sharing—and the alternative (electrical upgrades) costs 50-200% more while delivering only marginal practical benefit for most households. With proper load balancing configuration, a standard 100A UK supply comfortably supports two EVs charging at 5-7kW each overnight, providing 160-190 miles of range per vehicle by morning.

As multi-EV households become increasingly common (projected 15% of UK EV-owning households by 2027), load balancing infrastructure represents forward-thinking home electrical planning. Early adopters installing load-balanced systems in 2025 are not only solving today's two-EV charging needs but future-proofing for potential third vehicles, home battery storage integration, and the broader electrification of home energy (heat pumps, induction cooking) that defines the UK's net-zero transition.