Mira Sport Max 10.8kW Review: The Most Power Most Homes Can Wire For
The Sport Max is one of the best-selling electric showers in Britain, and the 10.8 kW version is about as much heat as a domestic shower circuit is asked to carry. Buyers love it. The catch is not the shower — it is whether the cable behind your wall can take it, and what 10.8 kW really buys you on a January morning.
Where the reviews line up
The evidence comes from three different places: the electric-shower roundup at Expert Reviews, six tradespeople answering a homeowner's upgrade question on MyBuilder, and 123 buyer ratings at Screwfix. They answer different questions, and between them they cover the decision.
On the shower itself the verdict is consistent. It is strong for an electric shower — Expert Reviews calls it outstanding and Screwfix buyers average 4.7 out of 5. Airboost, which mixes air into the spray, makes the flow feel heavier than the litres alone would suggest. Two honest negatives from Expert Reviews: it is loud with Airboost on, and some owners have reported reliability problems.
On fitting, the tradespeople agree on one thing above all: a 10.8 kW shower usually needs heavier cable than older 7–9 kW installations have. Several say 10 mm² where many older homes have 6 mm². Mira specifies a 45 amp supply rating for this model. Whether your circuit qualifies is an electrician's judgement on site, not something any review — or we — can tell you.
The physics sets the limit. By our arithmetic, 10.8 kW warms roughly 4.4 litres a minute to 40°C from winter mains water at 5°C, and about 6.2 in summer. That is the best an electric shower can do on a normal domestic supply. If it still sounds thin, the answer is a different kind of shower, not a different electric one.
The three reviews this summary is built from
- Expert ReviewsEditorial roundup by Stuart Andrews, September 2024. Calls it outstanding; flags noise and reliability.
- MyBuilder tradespeopleSix answers from electricians and plumbers on moving up to 10.8 kW. The cabling reality check.
- Screwfix4.7/5 from 123 buyer reviews, checked 4 October 2026 — on a page that sells it.
Before the review: which Sport Max is this?
The listings mix two generations. Mira's current single-outlet 10.8 kW is product number 1.1746.828 (with the 9.0 kW as 1.1746.827), per the Mira data sheet Wickes hosts. The older 2012-on 1.1746.008 is marked discontinued at Victorian Plumbing, though spares sites still list it. Both carry Airboost. There is also a Sport Max Dual (1.1746.830) with a rainfall head — a different product. Check the product number on the box you are buying.
Specification at a glance
| Spec | Figure | Confidence |
|---|---|---|
| Power rating | 10.8 kW at 240 V; 9.9 kW at 230 V | Mira data sheet (1.1746.008 issue) |
| Flow to 40°C, winter (5°C mains) | About 4.4 l/min at 240 V; about 4.1 at 230 V | Our arithmetic from Mira's kW figure — Mira does not publish a seasonal table we could find |
| Flow to 40°C, summer (15°C mains) | About 6.2 l/min at 240 V; about 5.7 at 230 V | Our arithmetic, as above |
| Flow as retailers list it | 4–8 l/min (Screwfix); 12 l/min maximum (Toolstation); 4.89 l/min (Victorian Plumbing) | Three retailers, three figures, none with stated conditions |
| Minimum maintained pressure | 1.0 bar (10 m head) | Mira data sheet. Screwfix lists 0.7 bar — Mira's figure for the 9 kW. Victorian Plumbing lists 0.2 bar static |
| Maximum pressure | 5.0 bar maintained; 10.0 bar static | Mira data sheet |
| Supply rating | 45 amp | Mira data sheet. Cable and MCB to be sized by an electrician |
| Terminal block | Takes cable up to 16 mm² | Mira data sheet |
| Water inlet and cable entry | Left side only: rising, falling or rear | Mira data sheet. No right-hand entry |
| Water connection | 15 mm compression, brass inlet; mains cold supply | Mira data sheet |
| Temperature control | Pressure stabilised, ±6°C — not thermostatic | Mira data sheet |
| Dimensions | 358 × 215 mm (H × W); depth 89 mm (Toolstation) or 75 mm (Screwfix) | Mira's sheet shows both depths, at different points of the case |
| Weight | 3.48 kg (Screwfix) or 4.37 kg (Toolstation) | Neither says whether boxed or with the kit |
| Head and rail | 120 mm head, 4 spray patterns; rail 400–640 mm adjustable; 1.25 m hose | Screwfix, Toolstation, Mira data sheet |
| Guarantee | 2 years; register online or on 0800 561 4513. Registering does not lengthen it | Mira guarantee page |
| Price | £228.99 at Screwfix (was £269.99); £308.99 at Toolstation | Both checked 4 October 2026. Mira RRP not found |
Expert Reviews
This is a buying-guide entry rather than a long-form review, and the page does not make clear whether the shower was plumbed in and used, so weigh it as an informed editorial judgement rather than a bench test. It ranks the Sport Max with Airboost fourth and calls it an outstanding shower, crediting Mira's Opti-Flo and Airboost — the latter designed, Mira says, to lift the flow effect by up to 30% by drawing air into the water.
The two downsides it names are the ones worth carrying into the shop. It describes the Sport Max as a loud shower with Airboost on, and notes that some users have had reliability problems. It priced the 9 kW at £230 and the 10.8 kW at £250 in September 2024. Its general advice matches the tradespeople below: higher wattages need larger cables and different fuses, so you cannot simply swap a smaller shower for a bigger one without an electrician.
Watch: Mira Airboost™ technology - how it works
An explainer of the air-mixing feature Expert Reviews credits — and the likely source of the extra noise it mentions. Manufacturer-style content, so promotional.
Watch on YouTube ↗MyBuilder tradespeople
This is not a review of the Sport Max as such; it is six tradespeople — including AMD Electrical and two named plumbing and heating firms in Sheffield and Swansea — telling a homeowner what moving up to 10.8 kW involves. That is the decision that matters most with this model, because most people buying it are replacing something smaller.
The answers converge. If the existing circuit is 6 mm² cable, the answer is probably no; with 10 mm² it may be yes. Several mention that the fuse or MCB would change too, one says additional devices may be required, and one advises simply replacing like for like at the old rating. Quotes ran from about £60 to £90 where the cable was already adequate, more if it was not. Treat those figures as dated and indicative. And treat the whole thread as the reason the sizing must be done by an electrician who can see your cable run, how it is installed and what your consumer unit will accept — those details change the answer.
Two practical fitting points from Mira's own data sheet belong here. Water and cable enter on the left side only — rising, falling or from the rear — so if your old shower was fed from the right, the pipe and cable will need moving. And a ShowerDoc answer on replacing an older Sport notes the newer unit is a direct replacement except for the bottom fixing hole, so expect to drill at least one new hole.
Watch: Mira Sport Shower Air Boost Installation
A short installation clip. Useful for seeing the left-hand entry positions before booking an installer; not a substitute for one.
Watch on YouTube ↗Screwfix
These are customer ratings hosted by a shop selling the product, so cite the number rather than lean on the tone. Toolstation shows a larger count — 220 reviews on the 10.8 kW and 248 on the 9 kW, with a five-star display — but we could not read an exact average there, so we have not used it as a score.
Screwfix buyers praise the power of the shower, say Airboost delivers a stronger-feeling flow without using more water, and describe installation as straightforward. The criticisms are about limescale upkeep despite Mira's Clearscale feature, and temperature needing careful adjustment — which is what you would expect from a pressure-stabilised rather than thermostatic unit. Older owner questions on ShowerDoc add a pattern worth knowing: 10.8 kW units that trip the circuit on the hottest setting, where the answers point to either an element fault or a circuit that is not up to the load.
Watch: Screwfix - Mira Sport Max with Airboost Manual Electric Shower 10.8kW
A retailer product film for this exact model and rating. Promotional, but a clear look at the controls and the kit.
Watch on YouTube ↗Strengths and weak points
What holds up
- 10.8 kW is at the top of the domestic electric range, so it gives about as much hot water as an electric shower can.
- Airboost makes the spray feel heavier than the litre figure suggests.
- Strong buyer ratings: 4.7/5 from 123 at Screwfix.
- Mira's own figures are clear: 45 amp supply, 1.0 bar minimum pressure, terminals up to 16 mm².
- Separate temperature and flow controls, four spray patterns, rub-clean nozzles.
- Widely stocked, so replacement and spares are easy to find.
What people complain about
- Loud with Airboost on, according to Expert Reviews.
- Some reports of reliability problems, and older owner threads about tripping on high.
- Winter flow is around 4.4 l/min at best. That is physics, not a fault.
- Needs 1.0 bar — more pressure than the 9 kW version's 0.7 bar.
- Left-side entry only; a right-fed old shower means moving pipe and cable.
- Two-year guarantee, and registering does not extend it.
Who it actually suits
Buy it if you have mains pressure of at least 1 bar, a shower circuit an electrician confirms will take 10.8 kW, and you want the strongest flow an electric shower can give. For a family bathroom where the shower is the main way anyone washes, the extra kW is worth having.
Look elsewhere if your circuit is 6 mm² and you do not want new cable run — the 9 kW Sport Max needs a 40 amp supply and 0.7 bar, and is often the sensible swap — or if you want thermostatic control or a quiet shower. Also look elsewhere if 4–5 litres a minute in winter will disappoint you. No electric shower fixes that.
On Part P: in England a new shower circuit, a consumer unit change and most new electrical work in a bathroom are notifiable under Part P of the Building Regulations. A registered competent person self-certifies and notifies the council for you, as Ribble Valley Council's guidance explains. Replacing a shower like for like on an existing, adequate circuit is generally not notifiable — but whether your circuit is adequate for 10.8 kW is exactly what you need an electrician to confirm.
What we could not check
- Cable and MCB size for your house. Mira gives a 45 amp supply rating; the tradespeople talk of 10 mm² cable. The correct size depends on cable length, how it is installed and grouped, and your consumer unit. A Part P registered electrician must confirm it.
- Mira's own seasonal flow table. We could not find one for this model, so the winter and summer figures are our arithmetic from the kW rating. Three retailers list three different flow figures with no conditions.
- The minimum-pressure conflict. Mira says 1.0 bar for the 10.8 kW; Screwfix lists 0.7 bar and Victorian Plumbing 0.2 bar static. We have used Mira's figure.
- Noise in decibels. Expert Reviews says it is loud with Airboost on; nobody publishes a figure.
- Whether Expert Reviews used the shower. Its entry reads as a buying-guide judgement; the page does not say it was installed and tested.
- Individual Screwfix review text. The review section did not load for us, so the themes above come from the page summary, not from reading every review.
- Toolstation's average score. We saw the review counts but not a numeric average.
- Mira's RRP for the current 1.1746.828 — not shown on the pages we could read.
- The videos. YouTube would not open for us, so each video was confirmed by appearing with the same title in two or more separate search listings. The listings did not name the channels.
- No Which? result. Which? tests electric showers, but its results are behind a paywall and we could not see a score for this model.
Sources last checked 4 October 2026. Prices, ratings and stock change — check them against the listing in front of you before ordering.