You’ve got a tough choice to make.

After doing all your research about boiler solutions for larger homes, you’ve finally whittled it down to two potential champions; a storage combi, or a system boiler with unvented cylinder.

Both are great solutions for larger homes, but which do you choose? Many of my customers often face the same question, which is why I’ve decided to help you out a little by putting together this blog post.

Aside from budget (obviously), there are some other factors to consider before you pick the ultimate winner.

Let’s first take a closer look at the storage combi, shall we?

Challenger 1: Storage Combi

Maybe you’ve heard in the past that combi boilers aren’t the best for large homes. There’s an element of truth in that, however thanks to the introduction of the storage combi, it might actually be a good solution.

Nowadays, a storage combi will allow you to run a bath AND two showers quite easily, due to the fact it has a storage capacity – this is a small heated tank stored with water so that when you turn on your taps, you can have access to heated water instantly.

You can also enjoy flow rates of up to 25 litres per minute, and heating output to radiators of up to 31kw. This is more than enough to heat a five-bedroom, two-bathroom home.

However, depending on the amount of power your storage combi can supply, you may notice a reduction in flow rate if a few people are using the hot water at the same time. NOTE: This is only really a problem if you have a particularly large family who are likely to be using the hot water simultaneously.

Pros of a storage combi

• Instant hot water that can easily heat a five-bedroom, two-bathroom home
• Flow rates of up to 25 litres per minute
• Central heating output to radiators of up to 31kw
• Incredibly energy efficient
• No need for cold water tanks in your attic
• Cheaper than a system boiler with unvented cylinder

Cons of a storage combi

• Flow rates can suffer if multiple users switch on the taps at once, depending on the amount of power your storage combi can supply.
• Bigger and bulkier than a normal combi
• Engineers may be unfamiliar with storage combis

Challenger 2: System boiler with unvented cylinder

Just like a storage combi, a system boiler will also take up a bit of extra space – in fact, more so, as you’ll have to find a cupboard or attic space to put the unvented cylinder. However, these are known as high-pressure systems which can provide all the heating and hot water your home will ever need, direct from the mains, with no reduction in flow rate.

Probably the greatest benefit of a system boiler with unvented cylinder, aside from the fantastic water pressure, is the fact that it is incredibly energy efficient. This is because cold water storage tanks simply aren’t needed (much like the storage combi).

Another great benefit of unvented cylinders is that you’ll be able to achieve true mains balancing at your water outlets, which reduces the risk of scalding – it’s also easy to include blending valves into the mix.

In fact, you’ll find with an unvented cylinder, your heating and hot water will run so smoothly that you won’t even have to think about it. The only real downside to the unvented cylinder option is the price, which is significantly more expensive than a storage combi.

Pros of a system boiler with unvented cylinder

• You can draw from several taps simultaneously with no reduction in flow rate
• There’s no need for a separate feed and expansion tank
• Suitable for larger properties that need a lot of hot water
• Pump included, making it faster and more energy efficient
• 25-year-guarantee on the unvented cylinder

Cons of a system boiler with unvented cylinder

• Takes up more space than a storage combi due to the cylinder
• Because the water is stored in a tank, it could take anywhere between 25 and 60 minutes to heat the water if you’ve been away.
• Much more expensive than a storage combi – the unvented cylinder alone can cost £1100
• Takes longer to install, as you need a full day just to install the unvented cylinder alone
• You may have to upgrade your incoming cold water mains supply pipe to 22m

Conclusion

If you have a large home and are faced with making the tough decision between a storage combi and a system boiler with unvented cylinder, I’ve (hopefully) just made things a little easier for you.

What you have to remember, is that a storage combi can comfortably supply a five bedroom, two bathroom home with up to 25 litres per minute of hot water. HOWEVER, if for instance, three or four family members were using the hot water at the same time, it’s possible you’ll notice a reduction in flow rate. Will this be a problem for you?

If so, your other option is a system boiler with unvented cylinder. This is known as a high-pressure system, and provides all the hot water your family will ever need direct from the mains, so your flow rate will always be consistent. The only drawback here is the price, as you’ll be paying £1100 just for the unvented cylinder alone.

Which will you pick?