Pumped Showers Vs Instantaneous Showers

There are two main kinds of electric shower used in Ireland, and they work in very different ways:

  • Pumped showers are fed with both hot and cold water. They use a mixing valve to blend them together to provide water at a comfortable temperature for the user.
  • Instantaneous Electric Showers are fed with cold water only. They use electrical heating elements to heat the water as it passes through the shower unit.

So which is better?

It depends. Let’s start with the instantaneous electric shower. The advantage of instantaneous electric showers is that they minimise waste because they heat only as much water as the user needs. Contrast this with a pumped electric shower – if you’re turning on the immersion just to heat some water for a shower it’s impossible to know exactly how long to leave the immersion on for to heat just the right amount of water for your shower. Too long and you’re wasting electricity; too short and the water will run cold before you’ve finished rinsing the shampoo out of your hair! On top of this, some heat is wasted as the water cools on its way from your hot water cylinder to your shower. All in all, instantaneous showers are the clear winner when you’re using the same power source for both your shower and your hot water tank.

The Case for Pumped Showers

The advantage of pumped electric showers is that your hot water cylinder can act as a storage vessel to store cheaper forms of energy for use later. For example, you can use discount-rate night time electricity to fill your tank with hot water and then use it in your pumped shower during the day. This works especially well if you have a well-insulated hot water cylinder that hods the heat in. Other options are to use kerosene or gas (usually as part of the central heating system) to heat the water. These fuels generally work out cheaper per unit of energy than daytime electricity (see image below). Best of all, you could use a heat pump, solar thermal, or surplus solar PV energy to heat your water. In the long run, these will be by far the cheapest options of all.

Heat Source		Cost (€/kWh of useful energy, Ireland)
Immersion (Day)		22.91
Instantaneous Shower (Day)		20.62
Immersion (Night)		10.66
Kerosene Oil		10.21
Natural Gas		9.8
Instantaneous Shower (Night)		9.6
Heat Pump (Day)		5.89
Heat Pump (Night)		2.74
Pumped showers are generally more cost-effective than instantaneous electric showers. The exception is when hot water is supplied by an immersion using day rate electricity. Data from https://www.seai.ie/publications/Domestic-Fuel-Cost-Comparison.pdf.*

Conclusion

If you’ll be using daytime electricity to heat your water one way or the other, then an instantaneous shower will be more efficient and more economical. However, pumped electric showers are the winner if you can find a cheaper source of energy to provide hot water for them.

Whatever kind of shower you have, you can save make big savings by changing the way you use it. Check out this post to learn how.

*Assumptions: Electricity Band DD; Natural Gas Band D2; Kerosene typical discounted price; Heat Pump Seasonal Performance Factor 3.5; Efficiency of 70% for kerosene and gas; 100% for instantaneous electric showers; 90% for immersion heaters.

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