Property heat mapping Guernsey

If your customers struggle with electrical installations, here are some essential insights that will benefit everyone.

Heat Loss Calculations

The key to effective installations. 

Oversized heating installations demand more load than the customer needs, significantly reducing network capacity.

So how can you help as many of your customers as possible get their electric heating installed?  Heat loss calculations.

Here’s an example.
Imagine a single electricity cable supplies five potential customers, each with property heat loss of 14kW. All five may want electric heating soon, and the current electricity supply cable can only provide 80kW of additional load.

If three of those customers have an oversized heating system – e.g. 24kW rather than 14kW – the capacity left for your other customers is just 8kW.

The result? The final two customers cannot have an electric heating system installation. And you lose business.

The good news is Guernsey’s electricity network is undergoing upgrades, but the energy transition is a journey that won’t be fully complete until at least 2050. This frustrating situation (particularly for your customers) could be reduced by performing an accurate heat loss calculation.

Contractors may simply replace e.g. a 36kW gas boiler with a 36kW electric boiler in a property with just 6kW heat loss. Consequently, a heat loss calculation would have left capacity for another 30kW installation from the same cable. Scale this across all your potential customers, and you’ll see why heat loss calculations are better for everyone.

A mechanical or ventilation engineer can carry out a heat loss calculation.

Electric heating customers


Electrification is in high demand, so timing is everything.

‘Additional load’ applications

As more people turn to electrical solutions, particularly for heating and EV charging, waiting times for these applications will inevitably increase.

Anyone needing a ‘change of existing load’ – for example moving electric heating from E12 tariff to Superheat tariff – also needs to submit an application.

Please advise your customers to plan early.

‘Supply line’ upgrades

As Guernsey Electricity maximise network capacity, more electrical solutions will need ‘three-phase’ connection meaning, in most cases, a supply line cable upgrade.

At the time of writing, ‘additional load’ applications and ‘supply line’ upgrades take around 9-months to complete.

Road closures

Upgrading or repairing our underground electricity grid likely requires road closures. This means upgrade timings are governed by Traffic and Highways, road embargoes, school holidays, emergencies, and other road closures.

See upcoming network plans 

Roadworks Guernsey

Why does it take so long?

We receive around 1200 additional load applications annually, and this is increasing year on year.

Electricity powers everything we do, so we can’t cut corners and approve electrical installations without engineers thoroughly assessing the network supplying the property. Depending on additional load required, this may include:

• The local low-voltage network
• The wider high-voltage network

Each application comes with unique considerations, challenges and outcomes, and often isn’t a simple job to turn around.

Why should we apply for additional load?
Like an extension lead, supply cables have finite capacity of available load.

Flickering lights would become the norm if installations took place without checking the network first. Plus there would be increased risks including faults, power outages, and many unhappy customers unable to run electric appliances.

Please apply for additional load in plenty of time to help keep your customers safe and enjoy reliable power.

Some applications may be refused if areas of the network are at capacity.

The best short-term solution may well be for customers to stay on fossil-fuel heating for 10-15 years until the local electricity network is upgraded. Off-peak solutions such as storage heating, or replacing heating oil with HVO, is something more customers are considering during the journey to 2050.

Fabric First

Easing the load

  1. Improve thermal performance through improved insulation
  2. Then Install lower-carbon heating solutions

‘Fabric First’ focuses on reducing a property’s heat loss and priorities energy efficiency over investing further in heating.

This isn’t only aimed at big-ticket insulation. There’s also a number of lower-cost alternatives that will help reduce energy bills and the amount customers need to spend to heat their property.

And if more buildings in Guernsey are well insulated with minimal heat loss, electricity grid investment would be significantly reduced too. The network reinforcements will electrify more homes and businesses quicker as the demand required by each property will be lower.

Home Energy Audits

Guernsey Electricity is offering a paid-for service to help domestic customers waste less energy in their homes and free up capacity across the grid.

Find out more about The Energy Savers

What can you do today? 

Install correctly sized boilers
Encourage property insulation
Set hot water timers to heat overnight
Property heat mapping Guernsey


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