[Closed] Electric water heater vs gas in 2020

I think gas is still about 3x cheaper than electricity so unless you can generate it all yourself it will still cost you a lot

I am going down this route. Just using the immersion as is at the moment but the grand plan is to be able to take advantage of off peak prices, PV etc using weather data and learned useage patterns / demands.

Edit: no mains gas, don't want to install oil seems short sighted.

What data are you getting and what system are you using to switch between gas and leccy?

I think gas is still about 3x cheaper than electricity so unless you can generate it all yourself it will still cost you a lot

I don't mind paying a bit more in overall terms for reducing CO2 emissions. I don't know how much of our usage goes on water heating but I might be able to model it because I know how many baths/showers people have and I could calculate the heat loss from the tank because I can measure how the water temperature drops with time.

I am building my own control system. Early stages of the software as little time but data wise I have loads of thermocouples, thermostats etc around the system. I will pull weather data from met office then use use usage patterns for how much energy I have to put into heat water each day. How far and complex I get depends on time.

Tank is unvented indirect. I don't have a gas boiler linked up (as not on mains) but if I did I would be using gas price Vs electric price Vs likely p.v. power available due to weather forecast and past data on PV output for given weather conditions / time of year. I would possibly also add a weighting to prefer electric over gas for the upto a cost margin.

Hmm. My hot water programmer simply operates a relay to turn the gas water heating on. So it would be easy as pie to attack that to a smart relay instead. And do the whole thing in software.

Coupled with a temperature sensor on the tank this would be much more useful than the current timer based system even if it were only on gas.

I have an Earthwise Solic 200 box that detects when i'm generating more power through PV than i'm using (most of the time at the moment, even with two working from home) - it offers that excess to the immersion heater so it keeps up with hot water use without using the gas boiler.

Jeff

At some point it will flip, we're not there yet but gas reserves are dwindling and I can see gas being a target for higher taxes as other sources of fossil fuel taxation reduces (e.g. car fuel). Ultimately gas will price it's self out of the market.

Not sure if gas might be more efficient though (despite the CO2 ramifications), lots more losses in generating the electricity, transporting it and reconverting it back into heat. Plus are electric systems on demand like a combi boiler or are they keeping the water up to temperature that way incurring more losses. Also don't forget we may be generating without coal at the moment (and long may it last) but there's still a lot of gas fired power stations out there.

I don't have a combi boiler, I have a tank. It's very well insulated though and doesn't lose much over 24 hours. Sometimes the gas boiler controller doesn't click on to heat it (replacement is ordered) and it takes a couple of days to notice.

Also my leccy is allegedly backed by renewable generation. Of course the actual electrons weren't necessarily energised by actual solar photons but the more money I give Ecotricity the bigger they get and the more renewable energy they can install. Obviously we wouldn't waste it, but if we pay them for renewable electricity then that's money that's not being spent on gas.

Hmm. My hot water programmer simply operates a relay to turn the gas water heating on. So it would be easy as pie to attack that to a smart relay instead. And do the whole thing in software.

I'm currently in a halfway house system. Still have the main central heating controller for timer etc but added in some relays and extra thermostat to spoof the controller on and off at different times. Best to get it all into software but the problem with many cheap muc or single board computers is the limited IO you soon end up multiplexing and with a wiring mess if your not careful. I have taken a step back and am trying to sort the electronics to make the software easier.

Our electricity mix is more and more renewable these days. So at some point the CO2 emissions from using the immersion heater to heat water would become lower than burning natural gas.

It could well be lower already. Average carbon factors for electricity and gas are now roughly the same, and you have to allow for a 10-15% loss in a gas boiler.

Average carbon factors for electricity and gas are now roughly the same

That's interesting - do they calculate that in terms of X tons of CO2 per MWh generated at the power station, or consumed at the home?

Also - you say average, is that per year or month? If it's roughly average over the year then there are bound to be periods where electric heating is greener.

That’s interesting – do they calculate that in terms of X tons of CO2 per MWh generated at the power station, or consumed at the home?

Also – you say average, is that per year or month? If it’s roughly average over the year then there are bound to be periods where electric heating is greener.

For electricity, there are separate factors for generation and for transmission/ distribution losses. It's normal to practice to add them when calculating a corporate emissions inventory. Not sure about gas.

They're annual averages so as you say there will be periods when electricity is lower. This year will be particularly low due to reduced demand and a consequent higher % of renewables.

As mentioned by ffej above I heat water with electricity, either diverted from solar PV system or using low cost overnight electricity.
My electricity tarrif is 5p/kwh for 4 hours overnight, making the cost similar to gas.
Electricity demand is generally lower overnight so if there is any wind then it will be high % renewable.
My motivation for electric heating was also CO2 reduction rather than £.

My energy supplier, Octopus, claims fully renewable electricity so apart fron cold showers that is about as good as it gets.

I don’t have a combi boiler, I have a tank. It’s very well insulated though and doesn’t lose much over 24 hours

I have a modern 125L unvented tank in my flat, compared to the old poorly insulated tank I had before it’s way more efficient.
I only use the nighttime immersion (economy 7 so cheaper) and it’s still very hot for a bath after a sink of washing up and some hand washing during the day.
Only ever turn the daytime immersion on if I know I’m using more water.

As someone has already said, unprecedented times at the moment for electric if you're on the right tariff. Ive seen people claiming around 3ppkwh average over a bill period in May 2020 and I've seen Octopus Agile as low as {minus} -10ppkwh in May. Not sure how it works with electric water heaters, but if you can do it overnight to draw off during the day then 5-6ppkwh for overnight water heating should have been achievable in normal pricing before all the coronavirus lockdown and excess electric (Octopus Agile}. Part of the requirement of Agile is that you have to be proactive pretty much every day, which most people won't want to be especially if they have a family who'll want electric on demand rather than constantly price watching.