Modern night storage heaters - how do they compare with a combi gas boiler?

cashferret · 24 May 2019 at 4:56PM

I'm about to get a combi boiler to replace my dying backboiler but someone just suggested to me that modern night-storage radiators might be an alternative, given that Ovo Energy have a scheme promoting them (albeit one that isn't in my area), which seems to be a vote of confidence.

Given the climate crisis I'd like to have an ecologically responsible system but I live in a 200-year-old flat which isn't possible to insulate to any great degree. I've been told that electricity (which is currently three times the price of gas) will be way too pricey and I've also been told that even the modern night storage heaters are glitchy and unreliable.

I use to have night-storage heaters 30 years ago and they were awful - I'd wake up at 4am too hot and by 5pm all the heat would be gone.

Has anyone got the new ones? Any thoughts?

Owain_Moneysaver · 24 May 2019 at 6:05PM

Modern night storage heaters with electronic controls (like Dimplex Quantum) might be less reliable long-term than the older sort. They should be better at heat retention. However, modern combi boilers probably won't last much more than 10 years.

Personally I'd go for a gas combi boiler if possible. It's the most controllable option, adds most value to the property, and gives instant hot water so you don't need a hot water cylinder - which in a flat can be a valuable space saving.

And burning gas in an A rated combi boiler is probably more environmentally friendly than charging storage heaters from gas-generated electricity, due to electricity distribution network losses (about a third) - and photovoltaics don't charge storage heaters overnight. The cost/eco balance might change if you had your own solar panels and could use a daytime charge to top up the heaters for the evening.

In an old flat, you might need to check that your electricity supply in the building can cope with storage heaters.

Martyn1981 · 24 May 2019 at 6:23PM

How big is your flat, and would you possibly consider air sourced heat pump heating (ASHP). If they don't heat water (you have a hot water tank), then they are relatively cheap. At their least efficient they are simply electric heaters, so no different to your heat storage idea (except no storage), and when the temps outside are higher, they can be 300-400% efficient*, with a UK average of a COP of 2.9 (for every kWh in of leccy, you'd get 2.9kWh of heat).

*300%+ efficient is misleading, they don't make heat, they move it, so 1kWh of leccy might shift 3 or 4kWh's of heat, so as far as you are concerned you get more bang for your buck, and that's all that matters.

From an environmental point of view, heating via leccy will only get cleaner every year as the carbon intensity of the grid steadily comes down.

cashferret · 24 May 2019 at 6:38PM

Hi Martyn - I'm partway up the building and none of my walls are accessible for a heatpump and I've also been advised that without my flat being well-insulated (which it never can be, given its nature), I'd put as much energy in as I'd get out.

Disappointing!

Martyn1981 · 25 May 2019 at 7:21AM

cashferret wrote: »

Hi Martyn - I'm partway up the building and none of my walls are accessible for a heatpump and I've also been advised that without my flat being well-insulated (which it never can be, given its nature), I'd put as much energy in as I'd get out.

Disappointing!

Fair enough, worth a try. But, regarding the insulation, that will be the same, hence why I was suggesting leccy heating (ASHP) at 3x the efficiency of storage heaters (also leccy heating).

How much gas do you use per year normally, that might be an interesting starting point?

cashferret · 25 May 2019 at 4:36PM

Last year I used 19,000 kWh with my inefficient, old back-boiler.

Martyn1981 · 25 May 2019 at 4:39PM

cashferret wrote: »

Last year I used 19,000 kWh with my inefficient, old back-boiler.

Holy frickin cow Batman!

I was not expecting that.

Martyn1981 · 25 May 2019 at 4:50PM

cashferret wrote: »

Last year I used 19,000 kWh with my inefficient, old back-boiler.

OK, I'm starting to get over my shock. I can think of one solution:

About 10yrs ago I asked my elderly neighbour (about 85) what was the quickest and cheapest way to get rid of the Mare's Tail* in my garden. He gave a funny smile/grin and said that as a younger man he'd asked a friend the exact same question, and the friend said ...... move!

*Turns out it's actual name is Horsetail, Mare's-tail is a wetland version, but the name typically used.

Back to numbers, so assuming the old unit is say 60-70% efficient, and a new unit is closer to 90%, then you'll be looking at around 13,000 kWh's gas, or 11,400kWh leccy.

Do you like your flat?

Owain_Moneysaver · 25 May 2019 at 5:33PM

Martyn1981 wrote: »

Back to numbers, so assuming the old unit is say 60-70% efficient,

It might be 60% efficient on paper but the true efficiency of a room-vented gas back boiler is much less due to the required combustion vent in the wall letting in cold air to compensate for all the hot air going up the chimney.

They were brilliant in their day and they lasted forever. Sadly their day has now passed.

I think I saw gas consumption halve when I swapped my Baxi Bermuda for an A-rated combi, and not having a draught whistling across the lounge made the whole house more comfortable. Also upgrading to a programmable thermostat was part of that - the house need never get freezing cold, but the heating doesn't need to be on daytime temps in the middle of the night.

Owain_Moneysaver · 25 May 2019 at 5:41PM

If you do want to consider heat pump / air conditioning, there are all-in-one air-con systems that don't have a separate outside unit. They work through two duct holes in the wall and can be installed with no outside access if necessary. Eg

https://www.airconco.com/buy/all-in-one-air-conditioner/
https://www.appliancesdirect.co.uk/p/air8sf/electriq-air8sf-air-conditioner

Martyn1981 · 25 May 2019 at 6:15PM

Owain_Moneysaver wrote: »

If you do want to consider heat pump / air conditioning, there are all-in-one air-con systems that don't have a separate outside unit. They work through two duct holes in the wall and can be installed with no outside access if necessary. Eg

https://www.airconco.com/buy/all-in-one-air-conditioner/
https://www.appliancesdirect.co.uk/p/air8sf/electriq-air8sf-air-conditioner

First off, thanks for that post, I'd never heard of this, so please don't think I'm being rude next.

But, secondly, if the unit is wholly inside, then presumably the huge volume of air also has to be processed inside, making it noisy. I note that the db figures given are similar to the outside unit I've got, which is akin to 'background daytime suburban noise'.

Also the price is scary, my 3.5kW unit was about £500 inc VAT and delivery (but not install).

But, negatives aside (sorry), thanks for introducing me to something new today, and based on your guesstimate about the boiler, then heating demand (v's gas consumption) might be closer to 10,000kWh, or possibly 3,500kWh of leccy via a ASHP (plus leccy for DHW heating).

Modern night storage heaters - how do they compare with a combi gas boiler?

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