ELectric boilers with PV

[grandfortune]

HI all,

just installed a 3.5Kw system on a friends house, his Gas boiler has packed up for the second time now and now he has his PV on he is wondering about having a Electric boiler.

they are a 50yr old couple who will be retiring in 10 yrs time and have a 3 bed semi.

just thought id post here before i look into it as i know you lot can probably answer better than me googling.


so does he get another gas boiler or go down the electric route?

Cheers Grand

 

[BruceB]

He/you need to do the sums. PV will not be generating much when space heating is being demanded from the electric boiler. Have a look at gas kWh provided in a year. I would be surprised if electric works out cheaper if there is already gas at the property. Better to have the diversity of gas CH + electric immersion + immersun I should think.

 

[TedM]

When you say "electric boiler" do you mean the sort that does central heating rather than just the DHW immersion? Those I have seen are usually in the 8kW range.

PV would make a very small direct contribution to this as the highest generation and demand will be at different times of year.

 

[FB.]

New boiler: £2500 = £250 per year with a 10yr lifespan.
Cost of annual service: £100.
Cost of parts/repairs at annual service: £100.
Cost of 12500kWh of gas @ 6p per kWh @ 90% efficiency to deliver 11250kWh of heat: £750.
Annual cost of electric to run pumps, fans and electronics: £50

Total annual cost of ownership of a gas boiler: £1250 per year, for ten years.

Cost of 11250kWh of electric per year (100% efficiency), @ 14p per kWh = £1575.

Annual difference: £325 in favour of gas. That doesn't even include the cost of the electric "boiler".

How much the solar could save is questionable, but if teh heating runs during daylight then I'd guess at half of each day's solar production in aurumn/winter/spring - so about £200 per year .

It'd probably be dramatically cheaper to run half a dozen (£25 each) 1.5kW convector heaters on timers (£3 each) and continue with the immersion element, than to fit an electric boiler. Just watch the maximum socket load in the property - mine's limited to 32A (7.5kW).

When my old Potterton finally gives up, I'm going to have to think very carefully about what I'll do because I would have problems with getting rid of the condensate because there are serious obstructions to adding a drainage pipe. I'd have to go for a soakaway and accept the risk of the condensate pipe freezing in winter and causing the boiler to do an emergency shutdown due to ice blockage - a problem which wreaked havoc on many thousands of people in the last two winters.

 

[Worcester]

This is where heat pumps come in - they are electrcicity multipliers (in the crudest sense) that 's the COP (Coefficient on Performance) put in 1 kWh get out 3-4kWh

Even then these still don't stack up against mains gas....

Daikin and Pnasonic both do high temperature output heat pumps that can retro-fit to existing CH radiators systems, their CoP is slightly reduced though.

@grandfortune, these people seem to the ideal 'TARGET' for the Green (raw) Deal :cowboy:

 

[grandfortune]

Thanks very much guys as always I flurry of answers and information. I'll advise them that they are best to stick with gas. Thru the green deal of course

 

[Vegelen]

Use a boiler manufacturers preferred installer to install a replacement boiler with 5 years free breakdown cover.
Viessmann, Worcester Bosch & Valiant manufacture excellent high efficiency condensing boilers.
Install your new boiler alongside a storage cylinder with an electric immersion heater connected to an Immersun.
Excess generated solar pv electricity can then be used to heat water in the storage tank, in preference to using gas or sending it to the grid, helping reduce your gas bills.

 

[The Launderer]

When my old Potterton finally gives up, I'm going to have to think very carefully about what I'll do because I would have problems with getting rid of the condensate because there are serious obstructions to adding a drainage pipe. I'd have to go for a soakaway and accept the risk of the condensate pipe freezing in winter and causing the boiler to do an emergency shutdown due to ice blockage - a problem which wreaked havoc on many thousands of people in the last two winters.

There are many things that can be done to help prevent freezing, including ensuring discharge pipe is big enough, decent insulation, trace heating, the new Worcester Bosch Condensesure looks like a decent product.

In any event a condensate line should be installed with a tundish so that the water cant back up into the boiler.

 

[The Launderer]

Use a boiler manufacturers preferred installer to install a replacement boiler with 5 years free breakdown cover.
Viessmann, Worcester Bosch & Valiant manufacture excellent high efficiency condensing boilers.
Install your new boiler alongside a storage cylinder with an electric immersion heater connected to an Immersun.
Excess generated solar pv electricity can then be used to heat water in the storage tank, in preference to using gas or sending it to the grid, helping reduce your gas bills.

Worcester Bosch Accredited installers will provide 7 year parts and labour warranties on most of the Worcester range

 

[SprintST]

Have you considered a solar PV switch connected to the immersion heater. The ECO 2 water heater system senses when there is any export curent and diverts it to your immersion heater. It therfore only ever uses the free (un used) solar pv power to heat the water.
You can get a system on ecoenergyproducts.co.uk on a paypal account

 

[grandfortune]

they have a combi boiler and its on its way out, they were wondering if an electric boiler would be more suitible,

Cheers
grand

 

[John Allen]

Have they considered a biomass boiler for CH and DHW?

 

[Gavin A]

they have a combi boiler and its on its way out, they were wondering if an electric boiler would be more suitible,

Cheers
grand

no. not for instantaneous hot water and heating, as the power draw when operating would be far higher than the PV can ever supply. They'd be far better off in money and carbon terms with a new combi. The only way they can benefit from the PV in this way is via a hot water tank and something like an Immersun (or indeed an Immersun) to power the immersion, or using an ASHP.