The Vokera Evolve 42C is a 42kW gas condensing combi and the largest combi in Vokera’s Evolve range. It was built for bigger homes with two bathrooms, where a smaller combi would struggle to keep up with hot water demand. It runs on natural gas or LPG without a conversion kit.
The Evolve range is no longer part of Vokera’s current line-up, which now centres on the Pinnacle, Synergy, Vibe MAX and Easi-Heat i boilers. Plenty of 42C boilers are still in service, though. This review covers what it does well, where it falls short and what to consider if you’re replacing one.
What Are The Vokera Evolve 42C’s Key Specs?
It’s a 42kW combi giving around 17 litres per minute of hot water, with A-rated 94% seasonal efficiency and a 1:7 modulation ratio.
| Specification | Vokera Evolve 42C |
| Boiler type | Gas condensing combi, wall-hung |
| Hot water input | 42kW |
| Central heating output | Up to 34.3kW at 80/60°C, 37.2kW at 50/30°C |
| Hot water flow rate | Approx. 16.6 to 17.2 litres per minute (Vokera quotes 17.2 at a 35°C rise) |
| ErP seasonal heating efficiency | 94%, A-rated |
| Modulation ratio | 1:7 |
| Dimensions (H x W x D) | 740 x 420 x 350mm |
| Weight | Approx. 39kg (dry) |
| Fuel | Natural gas or LPG, no conversion kit needed |
| Status | No longer in Vokera’s current range. Current Vokera combis are the Pinnacle, Synergy, Vibe MAX and Easi-Heat i |
What Is The Vokera Evolve 42C?
It’s the most powerful combi from Vokera’s Evolve family, a mid-range line-up that came in combi and system versions. Vokera is a long-standing UK and Irish boiler brand and part of the Riello group.
The 42 refers to hot water. When you run a shower or tap, the boiler can burn up to 42kW of gas to heat water straight from the mains.
Heating output to the radiators is lower, at up to 34.3kW at normal radiator temperatures. That’s still enough heat for most four and five-bedroom houses. People pick a 42kW combi for the hot water flow, not because their radiators need that much.
For its output, the casing is compact. At 740mm high, 420mm wide and 350mm deep, it fits in plenty of kitchen cupboards, which isn’t true of every high-output combi.
Still deciding between a combi and a system boiler with a cylinder? Our guide to combi, system and conventional boilers explains the trade-offs.
What Features Does The Evolve 42C Have?
Its key features are LPG compatibility without a kit, Active Combustion Control, a built-in CO monitor and OpenTherm support.
Can It Run On Natural Gas And LPG?
Yes, the 42C can be set up for either without a separate conversion kit. That made it a practical pick for rural homes off the gas grid, where large combis with LPG options are less common. Our LPG and oil boilers page covers off-grid options in more detail.
What Is Active Combustion Control?
It’s Vokera’s system for monitoring combustion and adjusting the gas and air mix automatically. It helps the boiler burn cleanly across its output range and adapt to different gas types without manual adjustment.
Does It Have A Built-In CO Monitor?
Yes. The Evolve has a carbon monoxide monitor built into the boiler.
It doesn’t replace a separate CO alarm in the room, and you should still have one. It just adds another layer of protection.
Does It Work With OpenTherm Controls?
Yes. With OpenTherm, a compatible thermostat tells the boiler how hard to work, rather than just switching it on and off. Paired with a suitable smart thermostat, the boiler can run at lower, steadier outputs, which suits condensing operation. See our smart thermostats page for the controls we fit.
What Kind Of Display Does It Have?
It has a backlit display with text menus. Settings and fault messages are easier to read than a bare code.
How Efficient Is The Vokera Evolve 42C?
It’s ErP A-rated with 94% seasonal heating efficiency, in line with most modern gas combis. If it’s replacing an old non-condensing boiler, you’ll notice the drop in gas use.
Its 1:7 modulation ratio is where it’s been overtaken. The boiler can turn down to roughly a seventh of its maximum heating output before it has to start cycling on and off.
Newer boilers often turn down further. That helps in well-insulated homes and on mild days, when only a little heat is needed. Vokera’s current Pinnacle range, for example, quotes 1:13.
Like any condensing boiler, real-world efficiency depends on the system. Lower flow temperatures, a clean system and good controls all help, and a yearly service keeps the condensate trap, heat exchanger and burner in good order.
What Are The Pros And Cons Of The Vokera Evolve 42C?
Its biggest pluses are strong hot water flow and LPG flexibility in a compact case, while its main drawbacks are narrow modulation and no longer being in Vokera’s range.
Pros
- Strong hot water flow for homes with two bathrooms
- Runs on natural gas or LPG with no conversion kit
- Compact casing for a 42kW boiler
- Built-in CO monitor and Active Combustion Control
- OpenTherm compatible for smarter, modulating control
- A-rated, 94% seasonal efficiency
Cons
- No longer in Vokera’s current range
- 1:7 modulation is narrower than many current boilers
- Oversized for most two and three-bedroom homes
- Vokera parts can take longer to source than parts for the biggest brands
- Still limited by your mains water supply, like any combi
What Size Home Does The Vokera Evolve 42C Suit?
It suits four and five-bedroom homes with a main bathroom, an en-suite and roughly 15 to 20 radiators. At around 17 litres per minute, it’ll run a shower well while other taps are in use. It can even manage two showers at once, though both will run at reduced flow.
That flow only arrives if your mains can supply it. A large combi on a weak mains supply performs no better than a smaller one.
If your home has three bathrooms, or two showers often run together, a system boiler with an unvented cylinder is usually the better answer. Read our guide on how to size a combi boiler before you choose.
How Much Does It Cost To Replace A Vokera Evolve 42C In 2026?
A straight swap to a current 40kW-class combi typically costs £2,500 to £3,300 installed, with more for a moved boiler or a conversion.
The guide ranges below include a standard flue, a magnetic filter, a system flush and basic controls. Prices vary from job to job, depending on the flue route, gas pipe size, the condition of the existing system and whether the boiler is moving.
| Type of job | Guide installed price |
| Combi to combi swap, same position | £2,500 to £3,300 |
| Combi swap with boiler moved or new flue route | £3,100 to £4,000 |
| System or regular boiler converted to combi | £3,400 to £4,600 |
These are guide figures only. A 40kW combi often needs a larger gas supply pipe than a smaller boiler, and that can add to the cost.
A survey will give you a fixed price. For more detail, see how much a new boiler costs, or boilers on finance to spread the payments.
What Are The Best Alternatives To The Vokera Evolve 42C?
For the same kind of hot water flow, look at the Vaillant ecoTEC plus 840 or ecoTEC exclusive 843, or other 40kW combis.
- Vokera Pinnacle: Vokera’s current high-efficiency combi, with a 1:13 modulation ratio and natural gas or LPG out of the box. The largest combi in the range is the 35C, so check it covers your hot water needs.
- Vaillant ecoTEC plus 840: 16.3 litres per minute at a 35°C rise from a 720 x 440mm casing.
- Vaillant ecoTEC exclusive 843: 17.8 litres per minute, Vaillant’s highest flow rate on a combi.
- Worcester Bosch and other 40kW combis: see our best 40kW combi boilers roundup.
- Vokera Evolve 30S: if a system boiler and cylinder suit your home better, read our Vokera Evolve 30S review and our best system boilers guide.
Is The Vokera Evolve 42C Worth It?
Yes, for a larger home it was a sound, good-value combi, but once one is over 8 years old, replacing it is usually the better option.
You get strong hot water and LPG flexibility in a compact case. Its main weakness is a narrower modulation range than current boilers.
If yours is under 8 years old, running well and serviced every year, there’s no rush. Once it’s over 8 years old, efficiency has usually dropped and faults become more common. A current 40kW-class combi or a system boiler is then often better value than paying for repairs.
Choose A Boiler Like It If
- You have four or more bedrooms and two bathrooms
- Your mains water supply has good flow and pressure
- You want instant hot water without a cylinder
- Your home runs on LPG and you want a high-output combi
Look Elsewhere If
- You have one bathroom, where a 30kW to 35kW combi is enough
- Two or more showers often run at the same time
- Your mains flow is weak
- You want the widest possible modulation for a well-insulated home
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Our experienced, professional and registered installers check your mains flow, gas supply and hot water use before recommending a boiler. That way, a large home gets the hot water it needs without paying for capacity it’ll never use.
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Frequently Asked Questions
Is The Vokera Evolve 42C Still Available?
No. The Evolve range no longer appears in Vokera’s current line-up, which is made up of the Pinnacle, Synergy, Vibe MAX and Easi-Heat i ranges. Existing Evolve boilers can still be serviced, but once one is over 8 years old, replacing it is usually better value than paying for repairs.
What Size Home Is The Vokera Evolve 42C Suitable For?
Four and five-bedroom homes with two bathrooms and a good mains water supply. For smaller homes, a 30kW to 35kW combi is usually a better fit.
Can The Vokera Evolve 42C Run On LPG?
Yes. It can be set up for natural gas or LPG without a separate conversion kit, which made it popular in off-grid properties.
Does The Vokera Evolve 42C Work With Smart Thermostats?
Yes. It’s OpenTherm compatible, so it works with OpenTherm smart thermostats that can modulate the boiler’s output, as well as standard on/off thermostats.
How Often Should A Vokera Evolve 42C Be Serviced?
Once a year, by a Gas Safe registered engineer. A yearly service keeps it efficient, checks the combustion and catches worn parts before they fail in winter.