Heat Pump & EV Charger Electrical Capacity: UK Home Energy Guide 2025

Heat Pump & EV Charger Electrical Capacity: UK Home Energy Planning Guide 2025

Installing both a heat pump and EV charger? You're not alone. The UK government's push for decarbonisation means millions of homes will need both technologies. But can your electrical supply handle them?

This comprehensive guide explains how to plan your home's electrical capacity for heat pump and EV charger coexistence, avoiding costly supply upgrades and ensuring both systems work efficiently.

The Challenge: Understanding Your Electrical Capacity

Typical UK Home Supply

Standard UK Supply:

• Single-phase: 100A at 230V = 23kW maximum
• Main fuse (cut-out): 60A, 80A, or 100A depending on property age
• Consumer unit: Typically 63A-100A rated

What This Means:

• A 60A supply = 13.8kW maximum total home load
• An 80A supply = 18.4kW maximum total home load
• A 100A supply = 23kW maximum total home load

Typical Power Demands

The Problem Scenario

Winter evening example (worst case):

• Heat pump running at 5kW (cold weather, high demand)
• EV charging at 7kW
• Cooking dinner at 4kW
• General lighting/appliances at 2kW
• Total: 18kW

With a 60A (13.8kW) supply, this would trip your main fuse. Even with 80A (18.4kW), you're at the limit.

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Solution 1: Load Management (Most Common)

What Is Load Management?

Load management (or dynamic load balancing) automatically reduces EV charging power when other demands increase. This prevents overloading your supply without requiring expensive upgrades.

How It Works:

1. CT clamp monitors total home consumption at meter/consumer unit
2. When load approaches supply limit, EV charger reduces power
3. When load decreases, EV charger increases power back
4. All automatic - you don't notice anything

Load Management Chargers for Heat Pump Homes

Zappi V2 (Best for Load Management)

• CT clamp included - Monitors home load in real-time
• Dynamic adjustment - Reduces from 7kW down to 1.4kW as needed
• Price: £800-£950 (installed)
• Why ideal: Aggressive load management, proven reliability

Wallbox Pulsar Plus with Power Boost

• CT clamp optional - Add Power Boost for £80-£120
• Dynamic adjustment - Reduces power automatically
• Price: £750-£900 (installed) + Power Boost
• Why ideal: Compact, reliable, excellent app

Ohme Home Pro

• CT clamp included - Built-in load monitoring
• Smart tariff integration - Combines load management with Octopus Intelligent
• Price: £900-£1,100 (installed)
• Why ideal: Best smart tariff optimisation + load management

Easee One

• CT clamp option - Equalizer add-on for load management
• Dynamic adjustment - Very smooth power reduction
• Price: £850-£1,000 (installed) + Equalizer
• Why ideal: Best for multiple charger installations

Real-World Example

Home: 60A supply, air source heat pump (5kW peak), 7kW EV charger

Outcome: EV still charges (just slower), heat pump runs normally, no supply trip.

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Solution 2: Scheduled Charging (Simplest)

Time-Based Separation

If load management chargers aren't suitable, schedule EV charging for times when heat pump demand is low.

UK Heat Pump Demand Pattern:

• Highest: 6-9am, 4-9pm (heating active)
• Lowest: Midnight-5am (most homes pre-warmed)

Ideal EV Charging Window:

• 00:30-05:00 - Heat pump usually idle, cheapest electricity
• Aligns with: Octopus Intelligent Go, OVO Charge Anytime, British Gas EV tariff

How to Set Up:

1. Car scheduling: Set departure time for morning, charge during off-peak
2. Charger scheduling: Use Wallbox/Ohme/Zappi app to set charge windows
3. Smart tariff: Let Octopus Intelligent or similar control charging automatically

Limitation: If you arrive home late needing a quick charge, the heat pump may be running - risk of overload without load management.

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Solution 3: DNO Supply Upgrade

When an Upgrade Is Needed

Consider supply upgrade if:

• Load management won't provide enough EV charging speed
• You have multiple EVs (2+ chargers)
• Ground source heat pump with very high demand (8kW+)
• Electric cooker + shower + heat pump + EV = frequent issues
• Future expansion planned (battery storage, more EVs)

UK DNO Upgrade Process

Step 1: Application

• Contact your DNO (listed on electricity bill/meter)
• Request supply upgrade (e.g., 60A to 100A, or three-phase)

Step 2: Assessment

• DNO assesses network capacity
• May need to survey property
• Timeline: 2-8 weeks for decision

Step 3: Quotation

Costs Vary By:

• Distance from transformer
• Network reinforcement needed
• Whether service cable needs replacement
• Your DNO (prices vary significantly)

UK DNOs:

• UK Power Networks (London, South East, East)
• Western Power Distribution (Midlands, South West, Wales)
• Northern Powergrid (North East, Yorkshire)
• Scottish Power Energy Networks (Scotland, North Wales)
• Electricity North West (North West England)
• SSE Networks (Scotland Highlands/Islands)

Step 4: Installation

• DNO schedules work
• May involve new cable from street to meter
• Typically 1-2 day installation
• Power outage required (usually 2-4 hours)

Three-Phase: The Ultimate Solution

Benefits:

• 69kW capacity (3x single-phase)
• Can install 22kW charger
• Heat pump, EV, all appliances with headroom
• Future-proof for full electrification

Drawbacks:

• Cost: £2,000-£10,000+ (network dependent)
• Time: 2-6 months typical
• Consumer unit replacement needed (£400-£800)
• May require new main cable

Who Needs Three-Phase:

• Large homes with ground source heat pump
• Multiple EV households (2+ chargers)
• Home battery + solar + heat pump + EV setups
• Future-proofing for full electrification

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Solution 4: Lower-Power EV Charging

When 3.6kW Charging Is Sufficient

Do the Maths:

• 7kW charger: 30-35 miles per hour of charging
• 3.6kW charger: 15-18 miles per hour of charging

Average UK Daily Driving: 20-30 miles

3.6kW overnight (8 hours): 120-144 miles added

For most UK drivers, 3.6kW is plenty for overnight charging.

Lower-Power Charger Options

Dedicated 3.6kW Units:

• Cheaper installation (smaller cable)
• Lower load on supply
• Still charges 80% of EVs overnight
• Price: £400-£700 installed

7kW Charger Set to 3.6kW:

• Keep full capability for when needed
• Default to 16A daily
• Increase for weekend long-distance prep
• Most smart chargers allow this via app

Recommendation: Install 7kW charger but use load management. Get full speed when available, reduce automatically when needed.

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Heat Pump Specific Considerations

Air Source Heat Pump (ASHP)

Typical UK Power Range: 2-6kW

Demand Pattern:

• Highest in coldest weather (-5°C to 0°C)
• Lower in mild weather (8-15°C)
• Near-zero in summer (hot water only)

EV Charging Impact:

• Winter: May need significant load management
• Spring/Autumn: Minimal impact
• Summer: Essentially no competition

Best Load Management Strategy:

• CT clamp at consumer unit
• Prioritise heat pump (essential comfort)
• Reduce EV charging as needed (can charge later)

Ground Source Heat Pump (GSHP)

Typical UK Power Range: 3-8kW (larger due to compressor size)

Demand Pattern:

• More consistent than ASHP
• Less affected by weather extremes
• But higher baseline power

EV Charging Impact:

• More consistent load throughout year
• May need more aggressive load management
• Or consider 3.6kW charging as default

Hybrid Heat Pump

Combines: Heat pump + gas/oil boiler backup

EV Charging Advantage:

• In coldest weather, boiler takes over (no electrical load)
• Heat pump load rarely at maximum
• Easier to manage alongside EV charging

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Consumer Unit Considerations

Space for Both Circuits

EV Charger Needs:

• Dedicated MCB or RCBO (32A for 7kW, 16A for 3.6kW)
• Possibly Type A or Type B RCD (check charger spec)
• 1-2 module spaces in consumer unit

Heat Pump Needs:

• Dedicated MCB (typically 16A-32A depending on unit)
• 1-2 module spaces

If Consumer Unit Full:

• Add small sub-board for EV charger (£150-£300)
• Or upgrade consumer unit entirely (£400-£800)

Upgrade During Heat Pump Installation

Cost Saving Opportunity:

If having heat pump installed, add EV charger at same time:

• Single electrician visit (saves £100-£150)
• Consumer unit work combined
• Cable routes planned together
• Load management configured for both

Ask Your Heat Pump Installer: "Can we include EV charger installation in the same project?"

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Smart Tariff Optimisation

Best Tariffs for Heat Pump + EV Homes

Octopus Intelligent Go:

• 7.5p/kWh during smart charging windows
• Works with Ohme chargers automatically
• Heat pump can benefit from low night rates too
• Best for: Ohme charger owners

Octopus Flux:

• Variable rates throughout day
• Export payments for solar
• Can schedule heat pump and EV for cheapest periods
• Best for: Solar + battery homes

Octopus Agile:

• Half-hourly pricing
• Can be very cheap (sometimes negative)
• Requires active management
• Best for: Tech-savvy users with automation

OVO Charge Anytime:

• Smart charging windows for EVs
• Reasonable standard rate for heat pump
• Best for: OVO existing customers

Optimisation Strategy

Morning (6-9am):

• Heat pump pre-heats house (on cheap overnight rate before 5:30am)
• EV fully charged overnight
• Both off during morning peak

Daytime (9am-4pm):

• Heat pump on economy mode
• EV not charging (at work anyway)
• If home: solar generation covers loads

Evening (4-9pm):

• Heat pump maintaining temperature
• EV not charging (peak rates)
• House coasting on morning's heat

Overnight (11pm-5am):

• EV charging (cheapest rates)
• Heat pump pre-heating (cheap rates)
• Load management ensures no overload

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Planning Your Installation

If Installing EV Charger First

Considerations:

1. Choose load management charger (even if no heat pump yet)
2. Install CT clamp at consumer unit (ready for future)
3. Leave consumer unit space for future heat pump circuit
4. Document supply capacity for heat pump installer

Recommended Chargers:

• Zappi V2 (load management built-in)
• Ohme Home Pro (CT clamp included)
• Wallbox + Power Boost (add CT clamp option)

If Installing Heat Pump First

Questions for Heat Pump Installer:

1. "What is my current supply capacity?"
2. "How much does the heat pump draw at peak?"
3. "Is there space for an EV charger circuit?"
4. "Should we upgrade supply now?"
5. "Can you install EV charger at same time?"

Get In Writing:

• Heat pump maximum power draw
• Remaining supply capacity
• Consumer unit spare ways
• Recommendations for EV charger

If Installing Both Together

Best Approach:

1. Combined assessment - Installer evaluates total load
2. Supply upgrade if needed - Do before installation
3. Load management included - Charger with CT clamp
4. Single consumer unit upgrade - If required
5. Coordinated commissioning - Both systems tested together

Cost Saving: Combined installation typically saves £300-£500 vs separate projects.

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Case Studies

Case Study 1: Victorian Terrace, 60A Supply

Property: 3-bed Victorian terrace, London Supply: 60A single-phase Heat Pump: Vaillant ASHP, 4kW typical, 6kW peak EV: Tesla Model 3

Challenge: 60A supply can't handle heat pump (6kW) + EV charger (7kW) + cooking (4kW) simultaneously.

Solution:

• Installed Zappi V2 with CT clamp
• Load management reduces EV to 1.4-3kW during peak heat pump demand
• Scheduled charging for overnight when heat pump idle

Outcome:

• No supply upgrade needed (saved £1,500+)
• EV fully charged every morning
• Heat pump never interrupted
• Total installation cost: £950

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Case Study 2: New Build, 100A Supply

Property: 4-bed new build, Bristol Supply: 100A single-phase Heat Pump: Samsung ASHP, 5kW typical, 8kW peak (larger home) EV: BMW iX3, MG ZS EV (two cars)

Challenge: Two EVs + large heat pump pushing supply limits.

Solution:

• Upgraded to three-phase supply (£3,200 total)
• Installed two Easee chargers with Equalizer load balancing
• Heat pump on dedicated phase
• Each EV charger can access 7kW, load balanced between them

Outcome:

• Future-proof for battery storage addition
• Both cars charge simultaneously
• Heat pump never affected
• Premium solution but comprehensive

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Case Study 3: Rural Cottage, 60A Supply

Property: 2-bed cottage, Cotswolds Supply: 60A single-phase (DNO upgrade would cost £8,000 - remote location) Heat Pump: Grant ASHP, 3kW typical, 5kW peak EV: Hyundai Kona Electric

Challenge: DNO upgrade prohibitively expensive. Must work within 60A.

Solution:

• Installed Ohme Home Pro with CT clamp
• Configured 3.6kW default charging (16A)
• Full 7kW available manually when needed
• Octopus Intelligent Go for overnight charging

Outcome:

• 3.6kW overnight adds 100+ miles (plenty for rural use)
• Heat pump never affected
• Electricity cost £40/month (EV + heat pump)
• No supply upgrade needed

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Frequently Asked Questions

Can I run a heat pump and 7kW EV charger on a 60A supply?

Possibly, with load management. A load-managed charger (Zappi, Ohme, Wallbox with Power Boost) will reduce EV charging power when heat pump demand is high. For most homes, this works well - EV charges slower during peak heat pump times but still fully charges overnight.

Do I need to tell my DNO about a heat pump AND EV charger?

Yes. DNO notification is required for EV chargers over 3.6kW. Heat pumps also require notification. Your installers should handle both notifications. This doesn't mean you need an upgrade - it's just informing the DNO of your load.

Will load management slow my EV charging too much?

Rarely. Most load reduction happens during evening peak (5-8pm) when you're unlikely to need fast charging anyway. Overnight, when you actually want to charge, heat pump demand is usually low and full 7kW is available.

Should I wait to install my EV charger until after my heat pump?

No need to wait. Install a load-managed charger now (with CT clamp). It will work at full speed currently and automatically adapt when the heat pump arrives. The CT clamp monitors total home load regardless of what's installed.

Is three-phase worth it for heat pump + EV homes?

For most homes, no. Load management solves the problem at much lower cost. Three-phase makes sense if: you have multiple EVs, want 22kW charging, have a ground source heat pump with high demand, or want to future-proof comprehensively. Otherwise, stick with single-phase + load management.

Can my heat pump installer also fit my EV charger?

Possibly. If they're a qualified electrician (NICEIC, NAPIT registered) and OZEV-approved, yes. Many heat pump installers can do both - ask specifically. Combined installation saves money.

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Summary: Your Action Plan

Step 1: Know Your Supply

• Check main fuse rating (on meter cutout)
• Typical: 60A, 80A, or 100A

Step 2: Calculate Peak Load

• Heat pump peak demand (check specifications)
• EV charger (7kW = 32A)
• Other high-demand appliances
• Add together - compare to supply

Step 3: Choose Your Solution

Step 4: Install with Future in Mind

• Choose load management even if not currently needed
• Leave consumer unit space for additions
• Document everything for future installers

The good news: Most UK homes can successfully run a heat pump AND EV charger on their existing supply with load management. Supply upgrades are only needed for the most demanding situations.

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Last Updated: March 2025 | Based on UK DNO requirements, BS 7671 18th Edition, and real UK installation data