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Does Chop-Cloc really reduce energy bills?

Can Chop-Cloc really reduce energy bills? A Quick Review

What if there was a device that could knock up to 30 percent off your heating bills without you even noticing the difference?

The Chop-Cloc, which hit the market last year claims to do exactly that simply by turning off your heating for a period every hour. The idea is that your heating’s not off long enough for you to notice a difference in how warm you are, but that every minute it off saves you energy and money.


The founder, Garry Stewart is almost evangelical about it, and judging by the number of awards it’s been nominated for – and won – it’s impressing others too. Never ones to have our heads turned without due cause, we wanted to see for ourselves.

We asked Nick Davies to test the Chop-Cloc in his home and let us know what he thought. Working at the renewable energy testing center Narec, he is something of a whizz when it comes to figuring out how, and if, stuff works. Chop-Cloc advises that any plumber can easily install it. Nick did it himself.

Does Chop-Cloc really reduce energy bills?

“I like the simple control knob, and that you get an immediate response if you increase the chop (say if you feel a bit warm) and the boiler switches off. Many modern thermostats don’t click off so the user doesn’t know what’s happening. It’s also good to see the green when the heating is on and the boiler is off – it makes me feel smugly efficient, but I suspect it may make some people feel cold!

“I found the ‘meet the choppers’ leaflet amusing, but of little value to be honest. My wife was somewhat less diplomatic; saying it was making fun of people who try and save energy and making them all out to be cranks!

“Time will tell how we get on with it – it’s a large house with a smallish boiler (it’s actually carefully matched to the building heat loss, meaning it has to work hard when it’s cold) so I don’t expect we’ll be using a 30-minute chop in winter. But at this time of year, as we enter the season we might. I plan to start with 15 minutes and I’ll let you know how we get on.”

After four and a half months, and several cold snaps (he lives in the northeast), Nick updated us again in January 2015:

Longer term view

“We’ve had the Chop-Cloc installed since September and used a 15-minute chop right through to late November. As the blurb suggests, we hardly noticed a difference in comfort because the radiators stay warm even when the boiler has been off for ten minutes or so. The 45 minute ‘on’ time is more than enough to get the system back up to temperature and although it’s too early to say if we have saved any fuel, I expect the boiler is more efficient when worked harder in intervals than slumbering continuously. It should certainly prolong the life of the fan.

“Over the Christmas holidays, it was great. We had relatives staying, so the heating was on all day. Normally if we go out for a walk on the beach etc, I’d turn the heating off and face a  long warm-up time when we got back. Instead, I turned the Chop-Cloc to 30 which maintains warmth in the system so the response is faster and you have warm radiators to come back to.

Using it this way certainly allows you to maintain a better level of warmth during the day, slowly heating the building core and raising the radiant temperature which is what makes us feel warm. This is a bit at odds with energy efficiency thinking (i.e. always turn off when you go out) but I really think a higher average radiant temperature in the internal structure allows you to have a lower room thermostat setting…

“Now the temperature has fallen to around zero we don’t generally use it as the house never got up to temperature with the time switch settings we have. As a rule of thumb, if it’s less than 5C during the daytime I’m leaving it with zero chops, but expect we’ll use it again in a few weeks.”

“Overall I’d say I’m quite impressed with it.”

On installation

“I found the unit straightforward to install, once I’d read the instructions and figured out which terminals to use! Our system has mains voltage control, so I used terminals 1 to 4. I think some plumbers might struggle with this especially if the boiler has volt-free switching like many combis do.

“The terminal space is pretty congested and a bit fiddly. It’s no worse than most solar controls, but not as much space as you typically get in heating programmers or thermostats. To make it a bit easier, I fitted a 4 core flex to it before fastening to the wall and connecting to the boiler. I expect many installers would appreciate if the unit came fitted with a meter of flex.”

The Chop-Cloc costs £69.99 (free delivery) from The Chopping Company Ltd.

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