Electric Combi Boiler

Empzurg

I've got Solar panels and battery being installed next week but was also looking at replacing our gas combi boiler. Intially I was just going for a new gas boiler but have started to think about getting and electric combi instead. One benefit of this would be we could loose gas all together and no longer face the standing charge.

However I'm not sure how it will work out with running cost, yes I'll be able to partially run it off the solar but of course I mainly want the heating at the points of the year when solar generation is at the lowest.

I don't have a hot water tank so that option isn't avaialble to me, what do people think think is it a wise economical decision?

QrizB

An electric combi boiler is not a good match to solar PV. A larger-than-average domestic solar PV installation might put out 6kW on a good day, but an electrix combi boiler will pull 18kW or more so even on a bright sunny day you'll be buying 2/3rds of your electricity from the grid.

Also, your main demand for heat is in the winter when it's cold and dark, not in the summer when it's wearm and sunny.

The energy costs for an electric combi are roughly 4x as much as for a gas boiler. For an "average" house with a 12000kWh/yr gas heating demand when burned in an 85% efficient gas boiler, gas (at the current cap) costs about £900 while the equivalent amount of electricity would cost £2900. Additional cost £2000.

I did some calcs a while ago for gas, E7 storage and single-rate electric heat here; the sums for an electric combi boiler will be similar. (I'll update them again when the October cap is published.)

Your savings will complrise the annual gas standing charge (£100) plus the annual biler service (say another £100). You're still £1800/yr out of pocket.

markin

If your a low Gas user and in a well insulated house you could follow this guy and try to store the heat under the house in 2 500L water tanks, The key difference being the 3kwh elements that can use the solar better and use off peak power.

https://forums.moneysavingexpert.com/discussion/6377030/ditching-gas-going-electric-immersion-only-a-wee-project/p1

Spies

An electric combi boiler would be the single biggest mistake you could ever make in your life time. 

Don't do it. 

70sbudgie

Empzurg said:

I've got Solar panels and battery being installed next week but was also looking at replacing our gas combi boiler. Intially I was just going for a new gas boiler but have started to think about getting and electric combi instead. One benefit of this would be we could loose gas all together and no longer face the standing charge.

However I'm not sure how it will work out with running cost, yes I'll be able to partially run it off the solar but of course I mainly want the heating at the points of the year when solar generation is at the lowest.

I don't have a hot water tank so that option isn't avaialble to me, what do people think think is it a wise economical decision?

Is ASHP an option for you? It would at least be more efficient than even the most efficient electric boiler.

Empzurg

Thanks for the info, thats definitely and electric boiler out of the equation.

As for an ASHP, the cost at the moment is just to prohibitive, even with the Government subsidy.

Patrol

My ground source heat pump uses something like 15-20kW on a winters day to heat my house (hard to be more accurate as my meter covers the entire household use, and the heat pump runs at 1.4-1.7kW per hour so I can't easily convert hours to kW). My house is a 2007 build with 150mm blocks instead of 100mm, has foil insulation under the roof tiles, 100mm underfloor insulation, andunderfloor heating downstairs so reasonably energy efficient. Other GSHP users on these forums almost invariably use more than the 3500-4000kW a year I think my heating consumes.

From what I have read well designed/installed air source heat pumps are less efficient than well designed/installed ground source heat pumps, and an electric combi is less efficient again.

Solar, as stated here, I find it does little to offset my winter heating costs. Batteries charging from economy 7 might be a better fit but I am guessing you'd need more than 20kW of storage to timeshift the bulk of your heating costs.

It would be interesting to know your daily electric kW use, how many kW of battery you are getting and your peak daily gas kW. That would help to validate the replies above?