Is It Cheaper to Use a Timer for Your Hot Water Cylinder?

If you’ve ever opened your energy bill and thought, “Where’s all this going?”, hot water is likely a big part of the answer.

In many UK homes, the hot water cylinder is one of the most energy-hungry appliances. But is keeping it running all day necessary? Or can a timer help reduce your bills without leaving you with cold showers?

We’ll explore what you need to know in this blog post.

What a Hot Water Timer Actually Does

A hot water timer controls when your immersion heater or boiler heats the water stored in your cylinder. Instead of running constantly, the heater turns on during set periods, like early morning or evening, when you actually use hot water.

Timers come in various types:

• Mechanical (manual dial)
• Digital programmable
• Smart (Wi-Fi enabled, controllable via app)

They can be added to both electric immersion heaters and boiler-fed cylinders.

How Much Energy Do You Actually Save?

When you leave your cylinder “always on,” it keeps water at a set temperature (usually around 60°C) all day. Even with good insulation, hot water cylinders lose a small amount of heat over time. This is known as standing heat loss.

Every time the water cools, the heater kicks in to reheat it, even if you’re not using any. That’s energy you’re paying for without getting anything in return.

Using a timer helps you limit those unnecessary reheating cycles. Instead of maintaining temperature 24/7, the system only heats water when you need it. That can save you 10–30% on water heating costs, depending on your usage and cylinder insulation.

Real-Life Example

Let’s say you use 3 kWh per day to maintain your cylinder temperature without using a timer. At an average rate of 24p per kWh (electric), that’s:

• 3 × £0.24 = £0.72 per day, or £262.80 per year

If a timer reduces this by just 20%, that’s over £52 saved annually, and likely more in households with irregular or lower hot water use.

When Timers Make the Most Sense

Timers are especially helpful if:

• You have predictable usage patterns (like showers in the morning or washing up in the evening)
• You’re on a standard or time-of-use tariff
• Your cylinder is older or poorly insulated
• You’re not home all day

However, if you’re on an Economy 7 tariff with cheaper nighttime electricity, you’ll want to set the timer to heat water during off-peak hours, usually overnight.

Bonus Tip: Combine with Other Savings

Using a timer is even more effective when paired with:

• Good insulation: Jackets for older cylinders can reduce heat loss dramatically
• Thermostat adjustment: Lowering from 65°C to 55°C (if safe) cuts heating time
• Low-flow fixtures: Reduce how much hot water you use in the first place

Cheaper, Easier, and Better

Yes, using a timer for your hot water cylinder is often cheaper and it’s one of the easiest changes you can make. It helps match your energy use to your actual needs, instead of wasting heat when no one’s around to use it.

Think of it like turning off lights in rooms you’re not in. It’s a small act, but it adds up, especially when it comes to heating dozens of litres of water each day.