First, identify your water system
Combi boiler: no hot water cylinder, no tanks in the loft. Mains pressure hot and cold, flow limited by the boiler output.
Unvented cylinder (such as a Megaflo): a large insulated cylinder, no cold tank in the loft. Excellent mains pressure both sides.
Gravity-fed: a hot water cylinder in an airing cupboard plus a cold tank in the loft. Pressure depends on the height difference, and it is usually low.
Heat pump or thermal store systems behave differently again and are worth checking individually.
Everything below follows from which of these you have. If you are not sure, look for a cold water tank in the loft, which is the fastest way to tell.
The shower types side by side
Supply-and-fit ranges assuming the shower area already exists and no major pipework rerouting is needed.
| Type | Supply cost | Fitted cost | Typical flow | Works with |
|---|---|---|---|---|
| Electric shower | £90-£400 | £280-£650 | 4-6 l/min | Any system, cold feed only |
| Manual mixer | £70-£250 | £250-£500 | System dependent | Combi, unvented, gravity + pump |
| Thermostatic bar mixer | £120-£450 | £300-£700 | System dependent | Combi, unvented |
| Concealed thermostatic valve | £200-£700 | £550-£1,200 | System dependent | Combi, unvented |
| Digital shower | £450-£1,400 | £900-£2,000 | System dependent | Most, with processor sited correctly |
| Power shower (integral pump) | £250-£600 | £450-£900 | 10-14 l/min | Gravity-fed only |
| Shower pump added to system | £200-£550 | £500-£1,100 | Doubles typical gravity flow | Gravity-fed only |
The compatibility traps
A power shower on a combi boiler does not work and can damage the boiler. Combis are already mains pressure and must not be pumped.
A big rain head on a combi will disappoint. A 250 mm head wants roughly 12 to 15 litres per minute, and many combis simply cannot deliver that hot.
An electric shower is unaffected by your hot water system because it heats cold mains water itself. That makes it the reliable option in a poor-pressure house, at the cost of flow.
Two showers running at once on one combi means neither performs. If that is your household pattern, an unvented cylinder is the real answer.
Old gravity systems can be transformed by a twin-impeller pump, which is far cheaper than changing the whole heating system.
Rain heads, handsets and dual outlets
A fixed rain head looks superb and is poor for washing hair quickly or rinsing a child. A dual outlet with a rain head plus a handset solves both and costs surprisingly little more.
Ceiling-mounted heads need pipework in the ceiling void, so they need planning before boarding rather than choosing at the end.
Concealed valves look cleanest but put the working parts inside the wall. We fit them with serviceable access in mind because a valve you cannot reach is a problem waiting to happen.
Thermostatic is worth the money regardless of type. It holds temperature when a tap runs elsewhere in the house, which matters most in homes with children.
What we recommend, by house type
Modern home with a combi: thermostatic bar or concealed valve with a sensibly sized head, matched to the boiler's actual hot water flow rate.
Larger home with an unvented cylinder: anything you like. This is the system that supports a big rain head and dual outlets properly.
Older home with a loft tank: either add a pump and fit a mixer, or fit an electric shower if you want simplicity and no pump noise.
Rental property: electric shower. It is independent of the heating system, cheap to replace and keeps working when the boiler does not.
Frequently asked questions
Can I fit a power shower with a combi boiler?
No. Combi systems are already at mains pressure and must not be pumped. A thermostatic mixer matched to the boiler's flow rate is the right answer.
Why is my shower weak even though the taps are fine?
Usually a gravity-fed system with insufficient head height, or a mixer trying to blend mains cold with tank-fed hot. Both are fixable, but the fix depends on the system.
Are digital showers worth the money?
They give precise, repeatable temperature control and neat wall plates. Whether that justifies the cost is personal, but they need the processor sited somewhere serviceable.
What flow rate does a rain head need?
A 200-250 mm head generally wants 12-15 litres per minute to feel right. Below that it feels like standing in drizzle.
Will you check my system before quoting?
Yes. The free survey includes checking your water system and pressure, because that determines which showers will actually perform in your house.