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Megaflo System and Combi Boilers [Side-By-Side Comparison]

Megaflo system Welcome to our quick guide to Megaflo cylinders. Here, we’ll help you understand whether your home needs a combi boiler or a Megaflow cylinder, and walk you through the costs of buying and installing a Megaflow system.

Before we proceed, however — if you’re wondering whether a Megaflo system is a boiler, the answer is no.

Megaflo is a range of stainless steel hot water cylinders produced by Heatrae Sadia. Whilst Heatrae Sadia do produce boilers (the Electric Flow), there are is no “Megaflow boiler”.

In fact, a Megaflo cylinder is just a part of the hot water system, and must work in conjunction with a system boiler.

What Is a Megaflo? Megaflo System Explained

A Megaflo system comprises a cylinder that stores domestic hot water. These cylinders typically work with system boilers, but could also operate with solar thermal energy or a immersion water heaters as a backup heat source.

Megaflo hot water tanks are connected to mains water supply, which is used to fill them up with cold water. As the system boiler heats water intended for the central heating system, this hot central heating water passes through an immersion coil inside the cylinder, thus warming the cold water inside the cylinder. The cylinder then keeps the water at the desired temperature thanks to its polyurethane foam insulation, and supplies it on demand when you open your taps or use the shower.

Heatrae Sadia produces a range of Megaflo unvented cylinder models; you can see our explanation of vented and unvented cylinders here. Note that Megaflo cylinders don’t require an expansion vessel, and come with a temperature and pressure relief valve that shuts off the boiler or immersion heater if the acceptable temperature or pressure limits are exceeded.

The key takeaway here is this — a Megaflo cylinder only stores hot water, it doesn’t produce it. So, you need a system boiler — not a combi boiler, mind you — to make the water hot.

Megaflo System & Combi Boiler Comparison

Wondering if you need a combi boiler or a Megaflow cylinder?

The answer is straightforward and unambiguous: If you have a combi boiler system, you don’t need — in fact, you can’t use — a Megaflo system. That’s because combi boiler systems don’t work with hot water storage cylinders — they are designed to supply hot water instantly, on demand. When you open your taps, a combi boiler simply heats the water coming from the mains, and that’s how you get hot water in your taps and showers.

But since combi boilers can only produce as much flow as the mains water supply pressure allows, they’re not suitable for larger properties with high demand for hot water. So, for instance, if your household ever runs 2 showers at the same time, your combi won’t keep up and all you’ll get is an unsatisfying drizzle from both showerheads. A combi may also not be suitable if your mains pressure is normally low.

To cut to the chase — if you need plenty of hot water, and often at the same time, a combi boiler won’t do. Instead, you need the following:

  1. A cylinder to store a large volume of hot water — i.e. a Megaflo system; and,
  2. A system boiler to heat the water in the cylinder

With this setup, you’ll always have plenty of preheated water stored at your disposal. However, note that a system boiler with a Megaflo system costs more to install than a combi.

When You Should Install a Megaflo System & Boiler

If the points below apply to your property, hot water systems with a Megaflo hot water storage tank is suitable:

  • Demand for high water pressure
  • Need to run 2-3 baths or showers at once
  • Sufficient storage space for a hot water tank
  • Mains water pressure of 1 bar (measured at 22mm mains)
  • 16 litre per minute (or higher) flow rate from your mains water supply

When You Should Install a Combi Boiler

Combi boilers are incredibly popular heating systems, and are simpler to fit. If the bullet list below describes your circumstances, a combi boiler with no hot water storage will be the most cost-efficient option:

  • Low water pressure
  • Typically only 1 tap or shower on at the same time
  • Focus on energy effiency
  • Short on space
  • Have a gas, oil, or LPG supply to the property

You can get on-screen fixed price quotes for a combi boiler using this form from Heatable.

What Size Megaflo Cylinder Do I Need?

Given the complexity and cost of installing a Megaflo system, you’ll need to speak to a qualified heating engineer. They’ll need to survey your home, factoring in the quantity of bathrooms and hot water demand. You can find out what size cylinder you need here.

If you need a new system boiler to go along with the hot water cylinder, you can learn what size boiler you need here.

You can also get boiler quotes from qualified engineers by clicking here.

The Cost of Installing a Megaflo System [Compared to a Combi Boiler]

The cost of installing a Megaflo cylinder, including the cylinder itself, all safety features, cylinder thermostat, and connections to the hot water system could range anywhere from £500-2,000, inc. VAT.

The prices for the cylinder itself will vary. As an example, a 210L Megaflo cylinder will cost around £600, inc. VAT (and even then, prices vary depending on the exact model). That’s before factoring costs for additional parts and labour. We’ve created a cylinder installation cost guide here.

Then, there’s the cost of the system boiler you need to heat the water in the Megaflo cylinder. So whilst the cost of a combi and system boiler is roughly the same, installing a system boiler + Megaflo cylinder will obviously cost more than simply fitting a combi.

Looking for a new boiler? Jump over to Heatable, an online boiler comparison company. They offer awesome deals on Worcester boilers. You can get prices on screen within 2 minutes using this quick, anonymous form.

Worcester Bosch Greenstar 4000

What’s Next?

Hopefully, our guide has cleared up the confusion about Megaflo systems and combi boilers. To reiterate — a Megaflo is a cylinder that works in conjunction with a system boiler, but it’s not a boiler itself. Meanwhile, a combi boiler works on its own and doesn’t require a Megaflo cylinder.

If you feel that we’ve missed anything, or have any questions, please leave a comment below and we’ll get back to you as soon as possible.

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