We have installed 12 mains powered smoke alarms in the last 12 months, so we feel that we have the authority on telling you what works and what doesn't!

Before we give our 5 best hard wired smoke alarm systems, we're going to reveal an overall winner, a runner up and one that you should probably avoidCheck out the table below.

Aico Ei141RC
Kidde Firex KF20
aico ei141rc
Kidde FireX Hardwire Smoke Detector

"Easy to install, 9V battery backup"

"Battery back up, low cost alternative"

"Terribly expensive for what it is"


Our preferred mains smoke alarm is the Aico Ei141RC, due to the fact that is well priced, is easy to set up and install and has a 9V battery back up in case of the mains power going down.

If you've got more time to read, then we're happy to tell you that we're going to now reveal 5 of the best interlinked smoke alarms. We base our rankings on:

  • Price
  • Ease of install
  • Quality

Naturally, all the systems we have installed has been professionally done by a suitably qualified electrician that is NICEIC qualified.

If you're needing something similar installing into your property, make sure the tradesperson you use is registered with NICEIC, Elecsa, Napit or another recognised body. You can read more about competent persons here.

Now that you have our preferred option, what about the rest? Sometimes referred to as an interlinked smoke alarm system by those in the trade, we now give our opinion on the 5 best mains powered units available on the open market.

1. Aico Ei141RC Mains Ionisation Smoke Alarm

Amazon's Choice for "Mains Smoke Alarm"
  • Manufacturer: Aico
  • Weight: 349g
  • Size: 18 x 15.4 x 6 cm
  • Cost: £
  • Quality: Excellent
  • Installation: Easy 

This one is our favourite. Easy to find, easy to install and very well priced. You can connect up to 20 of these smoke alarms, meaning they're really good for very large properties. This can be done easily by hard wiring all the detectors or by using the wireless capability.

It comes with a 9V battery back up in case the mains power goes down.

We also made a mistake (or our electrician did) by putting an AICO heat detector in the bedroom instead of a smoke detector. Fortunately, you can keep use of the base and just change the head, so it was a five minute fix.

(Tip:  Read our guide on maintenance to combat potential fires.)

  • Excellent value for the price
  • Available to buy from almost all hardware stores
  • Can fit up to 20 of these together
  • Not a well recognised brand internationally
  • A bit bulkier than other brands

2. Kidde FireX Mains Powered Smoke Detector

Kidde FireX Hardwire Smoke Detector
  • Manufacturer: Kidde
  • Weight: 340g
  • Size: 8.3 x 7.4 x 2.9 inches
  • Cost: £
  • Quality: Very Good
  • Installation: Easy 

Installation with this Kidde Firex detector is very easy. As long as you position the baseplate mounting appropriately, it goes straight on. In fact, if you have an older baseplate from Kidde, the baseplate screw positions are still the same, so you can do a like for like

Simply attach it on and then it locks in to place with a quick twist.

It comes with the 9V replacement battery and the device won't allow you to mount it unless you put the battery in. Very smart.

  • Can be interconnected with up to 11 FireX alarms
  • Unique “battery missing” lockout
  • Green light signal indicates it's receiving AC power
  • Some have complained of a chirping noise
  • It can be limiting if you have a bigger home
  • Kidde should supply a conversion matrix

3. Nest Protect 2nd Generation Smoke (Wired)

Nest Protect 2nd Generation Smoke
  • Manufacturer: Nest
  • Weight: 460g
  • Size: 5.3 x 1.5 x 5.3 inches
  • Cost: ££££
  • Quality: Excellent
  • Installation: Difficult 

We've talked about this one in our guide to the best carbon monoxide detectors and it deserves a place here too. Yes, it is expensive and it can be costly once you start connecting several units, but it is the most advanced smart device for home safety.

A major plus point if you're looking to upgrade is that the wired Nest system can be wired into the previous electrical wired system. The only difference is that the thermostat will need an additional wire installed. All you need is the 120V hot (black) and neutral (white) wires in the electrical box connecting to the plug-in pigtail on the Nest.

  • Very advanced, can be used with Alexa
  • You can interconnect and unlimited number
  • Constantly receives updates internally
  • Very expensive
  • Traditional systems can do the same job mostly
  • Will need a qualified person to install

4. First Alert SCO5 Smoke Alarm 

First Alert hardwired Smoke Detector
  • Manufacturer: First Alert
  • Weight: 295g
  • Size: 8 x 7 x 2.5 inches
  • Cost: ££
  • Quality: Very Good
  • Installation: Easy 

This is a combined smoke and CO alarm which also includes a battery back up. We used this model when we first started refurbishing houses. However, we were asked to supply the CO alarm separately, hence why we started using AICO ones instead.

It's a really good one for homes and larger HMOs as you can hook up 18 compatible devices.

In addition to electrochemical sensors, the device can pick up on smouldering fires though its photoelectric sensor.

As a bonus, it comes with an 'end-of-life' battery signal meaning you can replace the entire unit with a brand new one.

  • Can connect to other BRK or First Alert detectors
  • 10-year limited warranty
  • Can be heard by those with hearing issues
  • It's quite expensive compared to others
  • Some users complain of false alarms

5. First Alert BRK 9120B Hardwired Smoke Alarm

First Alert Hardwired Smoke Alarm
  • Manufacturer: First Alert
  • Weight: 180g
  • Size: 8.5 x 7.5 x 6 inches
  • Cost: £
  • Quality: Very Good
  • Installation: Easy 

Very much like the ones above, these are easy to install.

Be careful that you don't buy an older model. These tend to be the ones that people have been complaining about which gives off a false alarm. The current model (9120B) replaced the older model of the same smoke detectors.

You simply unscrew the old base plate, and install the new ones. After that,  just plug in the existing wires to the new detectors and twist them into place.

  • Tamper locking pins
  • Very light and easy to handle
  • Can fit up to 10 of these interconnected
  • Backup batteries don't come supplied
  • A few have complained of false alarms

Interlinked Smoke Detectors - where to place Them

As mentioned at the beginning of this page, we've done about 12 Houses in Multiple Occupancy (HMO) this past year. One of the main legal requirements when doing something like this is to install an interlinked smoke alarm system.

We always put smoke detectors in living rooms and bedrooms. Very rarely do we put a heat and smoke detector into a bedroom as we normally don't offer cooking facilities in the bedroom i.e. we run our HMOs on a shared amenities basis. This means that it is almost always in the kitchen that we have a heat detector instead of a smoke detector.

smoke detector placement

Smoke detector installed in the middle of a room

Naturally, as the wording suggests, these two types of detectors are interlinked, so if a fire starts in one room and sets of a detector, then the ones in every single other room will start beeping as well.

heat detector in the kitchen

Heat detector is installed in the kitchen

What's important is to locate a suitably qualified electrician that can offer this service for you. We've been paying between £1100 and £1800 including labour and materials for a full system installation. The larger the property, the more detectors are needed.

As per our suggestion at the very top, we bought some AICO Ei141RC ionisation smoke alarm from Screwfix. Remember though, once you've bought some of these, it's not the end of it. It's important that know how to maintain smoke alarms, wired or otherwise.