Instant hot water taps in a renovation

14 Jul 2016
Reaction score
United Kingdom
Some feedback. About two years ago I bumped into an old colleague, who was to totally renovate a 2 up 2 down terraced house in in nice part of south west London. He asked me some things as he wanted to save space inside the house. He was heavily insulating the house. It was to be all one room downstairs with two beds upstairs, the bathroom in the loft facing rear with dormer, and a single floor kitchen extension out the back. A small longish garden at the rear.

I suggested:
  • going all electric saving on gas meter space and the standing charge for the meter
  • Remove the mains gas pipe from the house.
  • A boiling water tap in the kitchen;
  • A 11kW instant water heater to go into a cupboard; next to the bathroom. 11KW-11.5kW is the highest KW on single phase;
  • An aerated Raindance shower head for the shower (no bath);
  • A normal aerated tap for the bathroom basin regulated to 4 litres/min, fed off the instant electric water heater;
  • Electric underfloor heating with stats (Heatmiser) in the living room and one in each bedroom;
  • An electric kickspace heater in the kitchen with an above worktop mounted switch;
  • An electric towel rail in the bathroom;
  • LED lights all around.
  • Of course low energy appliances.
  • I told him it would be far cheaper to install than a piped CH system with a gas combi boiler, enabling the money saved to be used on thicker insulation.
  • I told him it would be maintenance free, saving a lump each year to spend on electricity.
  • A combination oven/microwave to save space.
As the house was to be heavily insulated with low heat loss, heating demands would be low. The Raindance shower head would give a decent shower, with the boiling water tap eliminating a kettle in the kitchen, which takes up valuable worktop space.

I met him briefly a few weeks back. He showed me some pictures with the renovation being top class, looking cavernous for such a small house. He had thick foam insulation under the solid ground floor with electric heating under a wooden floor. The front of the house had internal insulation against the walls. Highly insulated front and rear doors. Triple glazing all through. The rear of the house had high performing external insulation, inc' the extension, with render over. The roof was not vented with very thick insulation. The ventilation was heat recovery. The electric meter and CU was over the front door in a fireproof cupboard that blended in.

He is delighted with the heating, only ever having to be on once or twice in 18 months for a short period, never upstairs, except the bathroom every now and then for heating towels. Also no wall rads which he loves. He says the Raindance shower is great with no waiting. The boiling water tap (not a quooker) he says is superb with no waiting for hot water. The taps cost was offset by not buying an electric kettle - he is the sort who would buy a top rated designer brand, so a real saving I suppose. he would buy a Quooker type of tap anyhow as he likes the latest sort of stuff (he could have had a normal tap with a cheaper, £110 or so, instant electric heater under the sink). There is no space taken up by boilers, cylinders or a gas meter, which is a great advantage.

The electric running costs? He said so low it is not worth mentioning. He doesn't keep a tag on the costs. When it is ouch he notices. The water is on a meter so low water bills as no dead leg pipe.

So, in some situations going all electric can work out better all around, especially where space is needed.
Last edited:
Sponsored Links
The electric running costs? He said so low it is not worth mentioning. He doesn't keep a tag on the costs.
Very interesting but you have found someone who doesn't care too much about money, lives in a small terrace house in a posh area of London and they said they haven't noticed the electric bill. For all we know the electric bill could be 1k a year!
£1K a year? You are having a larf now.
He does care about money. He saved in not installing a combi and piped heating system. He also has very low heating and DHW bills.

The heating is rarely on. An aerated shower head using little water and consuming little kW. Not much difference in hot water usage in the kitchen as the boiling tap merely replaced the electric kettle. Use of other kitchen hot water is minimal as the dishwater is piled up. Water usage is down so lower water bills. Also:
  1. About £100 saved a year from no gas meter standing charge.
  2. Savings on annual maintenance bills, as all is maintenance free.
  3. Lower water bills as less run-off as DHW dead-leg pipe is eliminated and use of an aerated shower head and basin tap.
That pays for a lot of electricity.

He is in a posh area, but is in a cheapish house for the area of course. He made the maximum use of space and ensured lower bills. He did say he ran cable to under the roof in case he puts on solar panels in the future. He ran cable from the CU and roof to a point in the rear garden in case the PV panels are connected and/or a Tesla type of Powerwall battery is fitted. So far he has no intention of fitting solar panels or a Powerwall battery. Depending on bills in the future he has the option.

In highly insulated homes where space is needed, all electric is worth considering, but using the right equipment.
Last edited:
Is there a question or something you want to debate?
It's good that what you've speced has worked. In the UK we need more people to insulate to a much higher level than regs. Electric heating is one of the best ways to use renewable energy as long as your provider is honest.

However many people don't have the budget to renovate their houses spending 10k on ewi to gain 100 a year on their bills.

Sadly as the mafia construction has so much say in policy nothing will change in the new build area either.
Sponsored Links
Without knowing his annual electric bill, it's difficult to understand the savings. I'm sure, certainly vs my drafts 1930s semi, they are significant, but I for one would love to know the saving, so a payback period could be calculated
Oh I'm sure you're correct, but talking about reducing energy bills and replacing gas with electric heaters, without knowing the annual spend means it's difficult to know whether he has made the correct design (I'm sure he has) and what the net benefit is financially
He did not live in the house prior to renovation, so no comparison of bills. External wall insulation was installed as the external wall needed work anyhow - it was only the back of a terraced house and the kitchen extension. It was a full renovation, so a new approach was looked at. As I highlighted in in my second post.
  • He saved in not installing a more expensive combi and piped UFH system, using the savings to spend on more insulation.
  • He saves valuable space within the house.
  • He has very low heating and DHW bills.
  • The heating is rarely on.
  • An aerated shower head using little water lowering water bills
  • Shower consuming little kW to other electric showers
  • Not much difference in hot water energy consumption in the kitchen as the boiling tap merely replaced the electric kettle.
  • Use of other kitchen hot water is minimal as the dishwater is piled up.
  • Water usage overall is down because of dead-leg pipes so lower water bills.
  • About £100 saved a year as no gas meter standing charge. That £100 pays for a lot of electricity.
  • Savings on annual gas/unvented cylinder maintenance bills, approx £100, as all is maintenance free, which pays for a lot of electricity for heating and DHW.
  • Approx £200 per ann saved to spend on electricity.
  • Lower water bills as less run-off as DHW dead-leg pipe is eliminated as instant DHW taps are used
  • Lower water bills by use of an aerated shower head and basin tap.
  • He has a confection hob which are about the same to sun as gas hob. Gas hobs in well insulated homes are not a good idea.
Those who have gas heating and DHW generally have electric appliances and electric kettles, as he has. The difference is:
  1. He has an air-tight and well insulated house, reducing heating demands.
  2. The air-tight and well insulated house gives greater comfort conditions, as drafts and cold spots are eliminated.
  3. His DHW consumption is reduced because of aerated shower head and taps and instant DHW outlets.
  4. Any difference in gas v instant electric water is negated, or maybe equalled, as no dead-leg DHW pipe is heated to then go cold. It is a long way from the ground floor to the bathroom two floors above.
He also has underfloor heating and no rads, a great boost when it is on of course, which appears very little.
Last edited:
I saw that, and understand the potential savings, however as already mentioned above, without knowing whether he is spending £100 or £1000 per month on electricity, it makes, at least for, it difficult to fully grasp the full financial benefit.

I understand you maybe don't have that info, but the point is still valid. At least to my mind it is.

Interesting information regardless though.
Thanks. Overall looking at it, he is better off all around from many angles - even having an ecoish type of house. I thought the 11.5kW electric shower would give poor performance, however he says it is fine using the aerated Raindance shower head. I did say leave space for another smaller instant electric heater in the cupboard with a cable(s) big enough to cope. He then could parallel up two electric heaters for the shower giving better performance. He could also switch one off in summer, isolating it electrically and water-wise. He did make provision, but so far he is happy.

The point is that I am bringing to people's attention that there is another way, instead of blindly going down the gas heating & DHW route. But the conditions have to be right:
  1. mainly a highly insulated house;
  2. installation of solar panels & powerwall type of battery if the insulation is not that great.
  3. Or both of above.
Last edited:
If it was a well insulated family house then I think it would be worthwhile installing PV solar panels and a PowerWall battery. A two bed terraced for two people? probably not worth solar panels and Powerwall. Those items may increase the value of the place though.
Last edited:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links