The Hidden Costs of a Cheap Electric Boiler: What to Check Before You Buy!

Electric boilers are one of the simplest ways to move away from gas. There's no flue, no burner, no combustion and no gas supply to maintain. So it's no surprise that the market is filling up with options at very different price points - from well-supported UK brands to unbranded units bought straight from overseas factory listings.

But the price of the boiler box is rarely the price of a working heating system. A low headline figure can quickly become a false economy once the missing parts, electrical work, engineer time and aftercare are added. This guide walks through what to check before you buy, so you compare what actually matters.

The one question to ask first

Instead of asking "how much is the boiler?", ask this:

"What is included in a system my engineer can actually commission?"

The total installed cost is made up of six things: the boiler itself, the hydraulic parts around it, the controls, the hot water performance you'll get, how easily it can be serviced, and the warranty and support behind it. A cheap boiler usually saves money on one of these and quietly moves the cost into the others.

1. What's actually in the box?

Many electric boiler manuals expect the installer to supply a range of parts separately. These commonly include:

• An automatic bypass
• Full bore isolation valves for the heating and hot water connections
• A filling loop or temporary filling connection
• A magnetic filter and/or scale protection

None of these are optional extras - they're needed for a safe, working installation. If they aren't supplied, they'll appear on your engineer's invoice, along with the time to fit them.

By comparison, the E.C.A. Arceus combination boiler comes with a documented valve kit: heating flow and return valves, a hot water outlet valve, a cold water inlet valve, a WRAS-approved filling loop and a pressure gauge. It also has an automatic bypass and automatic air vent built in. That makes quotes clearer and installations more repeatable. (Good filtration and water quality still form part of any properly designed system.)

Check: ask for the full list of what's supplied, and what the manual says must be fitted externally.

2. Can your electrics handle it?

This is the biggest hidden cost of all, and the one most often discovered too late. An electric boiler draws a lot of current, and it needs its own dedicated circuit with the right cable and protection.

Here's what the manufacturer's published schedule states for the Arceus models:

Model	Supply	Nominal current	Supply cable	Minimum MCB
Arceus 12 kW	230 V single-phase	52 A	3 x 10 mm²	B63
Arceus 12 kW	400 V three-phase	17 A	5 x 4 mm²	B20
Arceus 15 kW	230 V single-phase	65 A	3 x 16 mm²	B80
Arceus 15 kW	400 V three-phase	21 A	5 x 6 mm²	B25

A 30 mA RCD is also specified. Notice that a 15 kW boiler on a single-phase supply needs a minimum B80 breaker - so a 63 A supply should never simply be assumed.

Before any boiler is ordered, your electrician should confirm the maximum demand on your incoming supply and check with your network operator (DNO) if needed. If your supply needs upgrading, that cost belongs in the comparison - not as a surprise after the boiler arrives.

One advantage of Arceus is that both the 12 kW and 15 kW models are documented for either 230 V single-phase or 400 V three-phase supply, giving your installer more flexibility in how the system is designed.

Check: get the current draw, cable size and breaker rating for the exact model, and have a competent electrician design the circuit to BS 7671.

3. Is it the right size, or just the biggest?

Bigger isn't automatically better. An oversized electric boiler can push you towards a larger electrical supply than you actually need - adding cost for no benefit.

A common shortcut is to count radiators and multiply by 1.5 kW. It's a useful starting point, but real radiator output depends on size, panel type and the water temperature the system runs at. For example, a 600 x 1000 mm Type 22 radiator rated at 1,778 W at the standard test condition (ΔT50) produces roughly 1,330 W at ΔT40 and only around 916 W at ΔT30.

As a rough guide, around eight conventional radiators can support a 12 kW conversation, while nine or more should prompt a closer look at 15 kW. But the right answer always comes from a proper room-by-room heat loss calculation.

E.C.A. UK's own experience is that the 12 kW combi is the right starting point for most homes with one to three bedrooms and one bathroom, with 15 kW reserved for homes where the calculated heating load genuinely exceeds 12 kW.

Check: insist on a heat loss calculation before choosing the output.

4. Read the hot water figures carefully

Hot water flow rates are easy to make look better than they are. A figure like "7 L/min" means very little unless you know the temperature rise it was measured at.

Remember: a 30°C temperature rise is not 30°C water. With cold water coming in at around 10°C, a 30°C rise gives you 40°C at the tap. If you want hotter water, the flow rate drops. Raising the target from 40°C to 44°C reduces flow by roughly 12%.

When flow rates from different manufacturers are converted to the same conditions, the picture can change. The Arceus 15 kW publishes 8 L/min at a 26.9°C rise, which works out at approximately 7.2 L/min at 40°C - the strongest figure in the set of competing combis we reviewed on a like-for-like basis.

It's also important to be realistic. An electric combi supplies one hot water outlet at a time. If your home has several bathrooms or you need hot water at more than one tap at once, a system boiler with a correctly sized unvented cylinder is usually the better answer - and a good supplier will tell you so.

Check: ask for the flow rate and the temperature rise it applies to, and compare at the same conditions.

5. What controls does it work with?

A basic on/off thermostat will run most boilers, but better controls give smoother temperatures and closer comfort. Arceus accepts on/off or modulating room controls, timers and an outdoor weather sensor, and is OpenTherm compatible, allowing a compatible thermostat to communicate heating demand digitally. It modulates from 2 kW up to its set output.

A word of caution: be wary of anyone applying gas boiler savings percentages directly to an electric boiler. Real results depend on your home, radiators, settings and how you use the heating.

Check: confirm which thermostats and controls are supported before you buy.

6. What happens when it needs servicing?

The heating elements are the heart of an electric boiler, and limescale is their main enemy - especially in hard water areas like London and the South East. On some boilers, a single failed element can mean a much bigger repair.

Arceus was designed with serviceability in mind. The current service manual documents:

• A dedicated test mode to check each heating element individually
• Guidance on removing and cleaning limescale from the elements
• Replacement of individual elements without removing the main tank
• Published spare part codes and an annual service reminder

Built-in protection functions - including pump overrun, frost protection, pump and valve exercise and an 8 litre expansion vessel (larger than the 5 litre vessels found in many alternatives) - help look after the system between services.

Check: ask whether elements can be tested and replaced individually, and whether spare parts are listed and available in the UK.

7. What does the warranty really cover?

Warranty headlines can hide a lot. Some cover parts only, some split parts and labour across different periods, and some factory-direct units carry as little as one year.

Arceus comes with 3 years' parts and labour cover on the appliance, plus 10 years' cover on the heating elements. As with any warranty, registration, annual servicing and the current written terms apply.

Check: ask what's covered, for how long, whether labour is included, and what conditions apply.

8. Are the approvals real, and do they cover this model?

A logo on a website is not the same as an approval. A genuine approval has a number, names the models it covers, identifies who issued it and has an expiry date - and you can check it on a public register.

For example, the Arceus combination boiler range holds WRAS approval #2205321, covering the 12, 15, 18, 24 and 27 kW models, and is backed by a signed UK Declaration of Conformity covering electrical safety, EMC, RoHS and the Water Fittings Regulations.

Check: ask for the approval number and look it up yourself.

9. Who stands behind it in the UK?

Private-label electric boiler platforms are widely available from overseas factories, with custom logos and packaging offered to anyone ordering in volume. Factory listing prices can start from a few hundred US dollars. But a factory listing isn't a UK-supported product. The price doesn't include UK compliance testing, documentation, import costs, stock, spare parts, technical support or a meaningful warranty.

If something goes wrong, you'll want a UK phone number that gets answered, an engineer who can get the parts, and a manufacturer with a track record. E.C.A. is part of the Elginkan group, founded in 1951, has produced boilers since 2004 and exports to more than 60 countries - with UK technical support available on 0800 640 9988.

Check: find out who handles warranty claims, where spares come from and how to reach technical support.

Your pre-purchase checklist

• What's supplied in the box, and what must be bought separately?
• What current, cable and breaker does this exact model need - and can my supply handle it?
• Has the output been chosen from a proper heat loss calculation?
• What's the hot water flow rate, and at what temperature rise?
• Is a combi right for my home, or do I need a system boiler and cylinder?
• Which controls and thermostats are supported?
• Can the heating elements be tested and replaced individually?
• What does the warranty cover, for how long and on what terms?
• Is there a verifiable approval number for this model?
• Who provides UK support, spares and warranty service?

The bottom line

The cheapest electric boiler is only cheap if the price covers a complete, safe and supported heating system. Compare the whole installation - not just the box - and you'll avoid the costs that don't show up until later.

The E.C.A. Arceus range is available as a combination boiler, system boiler or heat-only boiler in 12 kW and 15 kW outputs. To talk through the right option for your home, call our UK team on 0800 640 9988 or explore the range on our website.

Figures quoted are taken from current E.C.A. Arceus manuals and published documentation. All electrical and heating installations should be designed and carried out by competent, qualified engineers in line with Building Regulations and BS 7671. Warranty terms and conditions apply.