Wondering if you need a more powerful boiler in your house?
Usually when homeowners ask me about this, it’s twofold. Some may have just recently moved, and strongly feel their home is underheated. In which case, they’re often looking for a boiler with a bigger output.
TIP: Check out my blog ‘3 Reasons Why Your Home Isn’t Getting Warm Enough’ if this applies to you.
On the other hand, some may just be in the market for a new boiler, and find some engineers are quoting a 30kW boiler, whilst others are quoting a 35kW. So, which is right?
Having been fitting boilers in Edinburgh for over 20 years, I’m here to help. Below, I’ve outlined some of the biggest considerations to help determine if you need a more powerful boiler in your house.
How powerful is too powerful?
Theoretically, most modern boilers are fully modulating. This means they only burn the gas they need. So, when the come on and it’s really cold and there’s 20 radiators to heat, they’ll fire up to their maximum capacity – say, 30kW. However, if it’s not too cold, the burner will come down to 10kW to keep energy down.
So, whether you have a 30kW or 35kW heating output, neither boilers will waste fuel.
And although I’d be happy to over-specify a boiler slightly – it’s always within reason. After all, we’d want to ensure your home is never under-heated. For instance, if you need a boiler that’s somewhere between 24kW – 25kW, I’d always take the 25kW figure and fit the relevant boiler, on Worcester this would be a 27kW as a 24kW would be slightly under-sized.
However, a 30kW would be going over the top. You’d be paying more for a boiler you don’t need. And the bigger the difference in kW, the higher the price.
TIP: A reputable engineer will measure your heat loss to help determine the boiler you need for your home. You can also check your boiler quotes to ensure different companies are all recommending the same output for your home.
What if you need a better flow rate?
When we talk about ‘over specifying’, a lot of the time we’re talking about the heating circuit. However, when looking at combis, the flow rate is also important. The more kW to the hot water, the higher the flow rate. You may want a higher flow rate so your boiler can easily handle a rain shower and a deep-filled bath.
Ideally, a higher flow rate is more suitable if you have a family home and more than one person wanting to use the hot water at once.
But, you can also overspecify on flow rate. For instance, if you have a small property with only one shower, you’d be crazy to fit a boiler with a flow rate of 15 litres per minute, when you only have 12 litres per minute of water coming into your home. You’d again be paying more for a boiler you don’t need.
Again, you’ll need a knowledgeable engineer. They should help you determine your incoming maximum water pressure, and test your current flow rate – and whether it can be improved. But there’s no point in specifying a boiler that can’t possibly fulfill its potential.
Advice from an experienced engineer
Do your research, and find a reputable engineer you can trust. You may wish to compare classic and compact ranges of boilers, and check places like the Energy Saving Trust website. Always get three independent quotes, and check the heat loss capacity of your house.
A good engineer will be able to measure your heat loss, tell you the figures you need to know, and answer all of your questions. They shouldn’t refuse to keep anything back.
Just two weeks ago, I didn’t get a job because the customer had an existing 35kW Ideal combi boiler. He wanted to replace it. I quoted on a Worcester Bosch 36cdi compact, with the same flow rate and the same heating output.
Instead, he asked me to quote on a Worcester Bosch 30i or an Ideal 30kW boiler. I didn’t want to do it, as I knew he wouldn’t get the same flow rate as he was getting at present. Because of that, I wasn’t happy to do the job – I felt it’d be substandard. I didn’t want him coming back to me saying it wasn’t as good as what he had. I wanted to give him the right thing.
The reason he wanted a 30kW boiler? Someone else had told him it’d be fine. He’d save £200, but I knew he wouldn’t be happy with it.
Sometimes getting all the figures will tell you how knowledgeable an engineer really is. Some will shy away, or just don’t want to spend much time on calculations and specifications. Some may just want to fit a boiler that suits them. Instead, they should want to listen to you and your individual needs.
TIP: If one engineer’s saying one thing, an someone else is saying another? Get a third quote.
Conclusion
Unsure if you need a more powerful boiler in your house? The tips above should help you determine if that might be the case. Remember, most modern boilers will be fuel modulating, so you won’t be burning energy you don’t need (that’s now a thing of the past).
However, you could be spending an extra £200 – £400 on a bigger boiler than you need.
Got any questions about the size of boiler you need? Let me know in the comments’ section. I’m always happy to help!
