Cylinder Sizing & Efficiency: Prime Boiler Care's Horsham Guide

When your central heating system starts letting you down—maybe the hot water runs cold too fast, or your gas bill seems too high—where do you look first? 

Like most homeowners in Horsham and the wider West Sussex area, you probably point straight at the boiler. 

While the boiler is the engine of your heating system, as a seasoned engineer, I can tell you a secret: one of the biggest bottlenecks to comfort and efficiency often lies in the forgotten component lurking in your airing cupboard —the hot water cylinder. 

At Prime Boiler Care, we specialise in making homes in the Horsham and Adur Districts warm and efficient. 

Here’s a detailed breakdown of why your hot water cylinder is more important than you think, and the three crucial factors that could be costing you money. 

1. Size Matters: Are You Running on Empty? 

The primary job of the cylinder is to store hot water heated by your boiler, ready for immediate use. 

If the cylinder is too small for your home, (or has excess scale inside the cylinder or on the coil itself, which I will cover in a separate blog post) you run into two major, expensive problems: 

The Cold Shower Problem 

This is the most obvious issue. 

If your cylinder volume (measured in litres) is inadequate for your family’s peak usage (e.g., morning showers), you will simply run out of hot water. 

As a general guide: 

 * 1-2 People need around 100 – 120 Litres 

 * 3-4 People need around 150 – 180 Litres 

 * 5+ People need around 210+ Litres 

The Efficiency Killer 

When an undersized cylinder runs out of water, the boiler must kick in immediately and run flat-out to reheat it. 

This results in short cycling—the boiler constantly turning on and off to chase demand. 

A properly sized (or even slightly oversized) cylinder allows the boiler to run for one longer, continuous, and highly efficient cycle to heat the entire tank, saving gas and wear and tear on your boiler. 

2. The Power of Modern Insulation Many older homes in Horsham and Adur still have decades-old copper cylinders, perhaps covered by a simple, loose insulating jacket. 

This is a massive hidden drain on your gas supply. 

A thin copper tank, even with a jacket, loses heat rapidly. That means your boiler has to fire up every few hours, even when the hot water isn't being used, just to maintain the temperature against the huge heat loss. 

The Modern Upgrade: Unvented Cylinders 

If you are due for a boiler upgrade or simply want to maximise efficiency, consider upgrading to a modern unvented stainless steel cylinder. 

 * Superior Insulation: Modern cylinders use dense, factory-injected foam insulation. 

This dramatically reduces standby heat loss, meaning the water stays hot for significantly longer.  

* Mains Pressure Hot Water: A key benefit of unvented cylinders is that they deliver hot water at mains pressure, giving you that powerful, invigorating shower experience that a gravity-fed tank cannot match. 

Engineer's Fact: Upgrading a poorly insulated cylinder can easily save a household £50-£100 per year on heating costs by simply preventing wasted heat. 

3. The Technical Gold: Heat Exchange Coil Surface Area 

This is the technical detail that engineers typically focus on, but it’s critical for new, efficient boilers. 

Inside your cylinder is a copper coil through which the hot boiler water flows to heat the surrounding domestic water. 

The surface area of this coil dictates how quickly and efficiently the heat is transferred. 

 * Old/Small Coil: Found in older tanks, these have poor heat transfer. 

This forces your boiler to run longer and hotter to heat the water, wasting fuel. 

 * Modern/Large Coil: Modern cylinders are designed with large, high-efficiency coils. 

This allows the boiler to run for a shorter time and can even operate effectively with cooler water—a crucial factor if you ever transition to a super-efficient condensing boiler or even a heat pump. 

The Takeaway: If your cylinder has a small coil, even the most expensive, efficient boiler will struggle to deliver hot water quickly. 

Prime Boiler Care's Advice: Act Before You Replace 

Before you commit to a major boiler replacement, ask yourself: Is my cylinder holding back my entire heating system? 

As your local heating experts in Horsham and the surrounding area, we always assess your entire system—including your radiators and your cylinder—to ensure any investment you make provides maximum comfort and efficiency. 

Don't replace an expensive boiler only to find your old cylinder is still the problem! 

If you are experiencing slow hot-water recovery, running out of water quickly, or simply want an efficiency audit of your entire heating system, we’re here to help. 

Contact Prime Boiler Care today to book an assessment: 

 * Service Area: Horsham District and Adur District areas. 

 * Phone: 01403 814602 

 * Website: andrewtyler.co.uk 

 * Address: Suite 54, Standby Business Center, Foundry Lane, Horsham, West Sussex, England, RH13 5PX