The Controls Are the Clue: Boiler Plus on a Glow-worm Quote
Photo: One Trick Pony from Stockholm, CC BY-SA 2.0, via Wikimedia Commons
If you have spent the past fortnight collecting boiler quotes, you will know the pattern. The first page is the boiler. The second page is the price. Somewhere near the back, in a font size that suggests embarrassment, is a line about controls. That line is where Boiler Plus lives.
Boiler Plus is not a Glow-worm scheme, a sales upgrade or a badge on the boiler. It is the set of minimum standards for gas boiler installations in England, introduced back in April 2018. It applies to Glow-worm installations in the same way it applies to every other gas boiler brand. If you are in Scotland, Wales or Northern Ireland, the rules are different, so check the local position before you compare quotes.
Boiler Plus in one paragraph
For a typical combi replacement in England, Boiler Plus asks for three things. The boiler must meet a minimum ErP space-heating efficiency of 92 per cent. The system must have time and temperature controls. And the combi must include at least one additional efficiency measure from a short list: flue gas heat recovery, weather compensation, load compensation, or a smart thermostat with automation and optimisation.
That is the whole policy in plain English. The complications come from how it is written into quotes. Some installers put every item on the page. Others fold the controls into a single line, reuse what is already on the wall, or leave the extra measure until you ask. The result is that two quotes for the same Glow-worm boiler can look wildly different — not because the boiler is different, but because the paperwork is.
What a compliant quote should name
A quote is a sales document, not a certificate, but it should still give you enough detail to check the job. Look for three things.
First, the exact boiler model and its ErP space-heating efficiency. Glow-worm has models that meet the 92 per cent threshold, but the model still has to suit your home and your hot-water demand. A quote that says only 'Glow-worm combi' is not giving you enough to compare.
Second, the controls package by name. That usually means a programmer and a room thermostat, plus a cylinder thermostat if you have a hot-water cylinder. If the quote says the existing controls will be retained, ask whether they actually meet the standard and are compatible with the new boiler. Reusing controls is not automatically wrong, but it should be a considered decision, not a shortcut.
Third, the additional measure for a combi. The quote should say which one is being fitted and include the parts. 'Smart thermostat included' is not enough on its own. The thermostat has to meet the Boiler Plus definition of automation and optimisation, and the model should be named.
What each item actually does for your bill
Time and temperature controls are the basics. The programmer sets when heating comes on and off. The room thermostat sets the target temperature. Together they stop the boiler firing when there is no demand, which is the boiler interlock. Without proper controls, a condensing boiler can spend more time at high flow temperatures than it needs to.
Flue gas heat recovery is a passive heat exchanger on the flue. It captures heat from the gases leaving the boiler and uses it to preheat the cold water going into the combi. There are no moving parts, and it is particularly useful in homes that use a lot of hot water. It will not turn a combi into a thermal store, but it can trim the gas used for hot water.
Weather compensation uses an outdoor sensor to adjust the boiler flow temperature according to the weather. On a mild day, the boiler runs cooler and more steadily. On a cold day, it lifts the flow temperature. Condensing boilers work best when the return water is cooler, so this can improve efficiency and reduce cycling.
Load compensation works from inside the home rather than from an outdoor sensor. It adjusts the flow temperature based on the room temperature and the demand from the controls. It can be a good fit where running a sensor cable outside is awkward, and it keeps the boiler from blasting away when the house is already close to temperature.
A smart thermostat only counts for Boiler Plus if it offers automation and optimisation. In practice, that means it can learn patterns, use geofencing or adjust settings automatically to reduce energy use. A basic app-controlled thermostat may be smart in the everyday sense but still fall short of the Boiler Plus definition. That is why the model matters.
Why it can look optional
Boiler Plus is mandatory for gas boiler installations in England, but it does not always feel that way when you are reading quotes. Installers often treat controls as add-ons because that is how the pricing works: the boiler is the headline, the controls are the extras. Homeowners sometimes choose the cheaper quote without realising the cheaper quote has left something out. And enforcement runs through building control and competent-person schemes, so a missing line does not always get flagged before the van arrives.
None of that makes the requirement optional. It just means you have to read the quote like a checklist rather than a brochure.
Red flags on a Glow-worm quote
Be wary if the quote does not name the controls at all. Be wary if it says the existing thermostat will be reused without checking whether it meets the standard. Be wary of a smart thermostat with no model name, or a combi quote with no additional measure listed. Be wary if there is no ErP efficiency figure, no commissioning note and no mention of Building Regulations notification. And be wary of a price that is far below the others with no explanation — sometimes the difference is labour, but sometimes it is a missing control or a missing measure.
Five questions to ask before you pay a deposit
- Which Boiler Plus additional measure are you fitting, and what is the make and model?
- Will the quote include a new programmer and room thermostat, and a cylinder thermostat if I need one?
- Does the smart thermostat meet the automation and optimisation criteria, and can you show me how?
- Will you notify Building Control or put the job through your competent-person scheme, and will I get the certificate?
- What flow temperature will you set, and will you walk me through the controls before you leave?
The bottom line
Boiler Plus is not glamorous. It will not make a boiler look better in a photo. But it is the difference between a quote that is complete and one that is merely cheap. If you can point to the boiler efficiency, the controls and the extra measure on the page, you are in good shape. If you cannot, ask before you pay a deposit. A good Glow-worm installer should be able to explain every line without reaching for the brochure.
