So now I have a solar PV system how do I make the most of it???

stone248

First post so go easy...….hopefully having solar installed and going for a 6.8kw system with tesla powerwall. We have an old house which requires a complete overahaul from an old single pipe gas central heating new boiler etc etc cost £7000. we were just wondering if anyone has installed the above system and gone completely gas free (apart from cooking, im not losing the gas for that) so the house will be heated and run via the solar PV system and the grid.  Also any other comments that might be relevant are always welcomed 

cannonballdaze

Hi, I'm assuming that your 6.8 Kw system will generate around 5,000 KwH pa (my 4 Kw generates 3,000 KwH)
My well insulated (EPC B+) house uses 10,000 KwH of gas pa for heating only (no cooking).
You're going to have to have super-duper insulation to have a chance of heating the house with the 5,000 KwH from the panels.

ABrass

stone248 said:

First post so go easy...….hopefully having solar installed and going for a 6.8kw system with tesla powerwall. We have an old house which requires a complete overahaul from an old single pipe gas central heating new boiler etc etc cost £7000. we were just wondering if anyone has installed the above system and gone completely gas free (apart from cooking, im not losing the gas for that) so the house will be heated and run via the solar PV system and the grid.  Also any other comments that might be relevant are always welcomed 

Why gas for cooking? Presumably for the gas hobs, but induction is just as good as Gas, easier in many ways. That way you could drop the gas entirely.

Are you planning a heat pump or resistive heaters? As mentioned earlier you're looking at a lot of electricity to heat a house and whilst your solar panels will make a dent in that, it'll be mostly at the wrong time of year.

Coastalwatch

Good post!

Apart from an old house requiring a complete overhaul we've just completed the path you are now embarking upon. As to what we arrived at would suit your situation is another matter entirely.

We've a fifty year old cavity walled bungalow, but suspect much of the path we've travelled will apply to your situation as well, like maximising insulation together with researching what system for heating  might prove most suitable.

Great that you've a sizeable PV array and a powerwall battery so half way there already!

Being a two bed dwelling we were able to replace our GCH system with two air to air heat source pumps for space heating, circa £3k. Hot water via an emersion thermal store, circa £1k.

The last gas item replaced was the hob for an induction version so the gas supply will be capped just as soon as can be arranged and ditch the daily standing charge for this.

Along with Air Source Heat Pumps there are also Ground Source Heat Pumps as options for heating. The latter being more costly but covers for hot water too and is generally eligible for RHI subsidy (If that's the right phrase)!

I'm sure others will join in with useful advice and there are several threads with oudles of information and opinion on here to explore should you wish. This one should be interesting.

https://forums.moneysavingexpert.com/discussion/6145030/gas-combi-boiler-needs-replacement-i-have-pv-what-options-are-there#latest

Enjoy the ride.

Richmc

Gas for cooking is always best, we have the usual electric oven with gas hob, now the good bit it runs on FloGas propane a 19Kg cylinder lasts around two years so is very economical (don't go for Calor it's much more expensive), and obviously there is no standing charge to pay, just the initial cylinder deposit. Most hobs now come with propane jets for the switch over.
If you intend using the power wall for heating I'm afraid you will be disappointed, Trouble is during the winter when you need the heating most you won't generate enough power, short and dull days will see to that. Air or ground source heat pumps are the real alternative, and they work best with under floor heating systems. Alternatively go for a gas tariff that has no early cancelation charge and only have it from September to May, you won't need it during the summer so just cancel it if you get an unseasonal cold snap you can fall back on electric heaters.
Have fun!

Exiled_Tyke

Richmc said:

Gas for cooking is always best, we have the usual electric oven with gas hob, now the good bit it runs on FloGas propane a 19Kg cylinder lasts around two years so is very economical (don't go for Calor it's much more expensive), and obviously there is no standing charge to pay, just the initial cylinder deposit. Most hobs now come with propane jets for the switch over.
If you intend using the power wall for heating I'm afraid you will be disappointed, Trouble is during the winter when you need the heating most you won't generate enough power, short and dull days will see to that. Air or ground source heat pumps are the real alternative, and they work best with under floor heating systems. Alternatively go for a gas tariff that has no early cancelation charge and only have it from September to May, you won't need it during the summer so just cancel it if you get an unseasonal cold snap you can fall back on electric heaters.
Have fun!

But this isn't green is it?  A modern induction hob is relatively efficient and will be powered by some proportion of greener/renewable energy which is surely an important aim?    

I also query whether gas is always best - the amount of energy which is wasted is very significant. A few years ago (so yes the price difference will not be valid now) I compared the cost of boiling a litre of water in my electric kettle to that of my (gas) stove top kettle. Even though gas was around four or five times cheaper (I can't remember the numbers) I found that the stove was less than 10per cent cheaper to run.   So there is a fair chance that there will be circumstances where gas isn't best (particularly say if you cook in the middle of the day and can make good use of Octopus Agile)

On another note, I'm glad you've raised the issue of heating (especially in winter). Sadly most houses still need vast amounts of heating (I still have major insulation issues in my house which are yet to be sorted e.g a bedroom over the garage with minimal insulation between the two) and so for most of use this will be far and away the higher proportion of energy used.  I consume around 2500kWh or electricity a year but nearly ten times that on gas for heating, hot water and cooking.  Even with very efficient heat pumps to reduce the heating energy consumption to say around a third of gas CH,  PV (as you correctly point out) will barely touch this need especially when it's needed most in winter. 


Finally to go back to the original question here, I don't know how much Powerwalls are at the moment but when I was looking they were one of the more expensive battery options and nowhere near financially viable.  I figured there was no way it could ever pay for itself. 

Richmc

"I also query whether gas is always best" - Ask any chef.
"But this isn't green is it?" - Nope, just gives better results.
Powerwall is defiantly NOT green and lithium ion is evil, first the raw materials come from third world countries mined under very poor working conditions, it's poisonous and the workers have very little protection. Next the processing has to be carried out at many different locations resulting in the product traveling twice around the world, lots of fuel miles there. Thirdly lithium ion batteries are dangerous, the Texas fire fighters (my nephew is one) have been ordered NEVER to attempt to extinguish a fire involving them (car or domestic) they burn at temperatures similar to burning magnesium and give off deadly toxic fumes so imagine the cost of insuring a Tesla car that can be written off after suffering very minor damage. Lithium ion batteries cannot be recycled as yet and have zero scrap value. And to produce one ton of lithium uses 1 million gallons of water! Compare this to lead acid batteries, made from common chemicals and materials not that pleasant ones but handled correctly totally safe. Sealed gel acid batteries will not give off inflammable or corrosive vapours. They will not last as long as lithium ion batteries but here's the rub they can be 100% recycled and you will get a very good price for them, offsetting the shorter life by miles.

Guess what I have in my Wattstor system :-)

edit - Forgot to say propane is the most environmentally friendly fuel available zero greenhouse gas production, apart from transport contributions.

Exiled_Tyke

Richmc said:

"I also query whether gas is always best" - Ask any chef.

For much (not all) of my professional 'cheffing' life I used gas but I wouldn't insist on it now especially as how improved electric hobs have become. 

Richmc

But is your electricity 100% green generated? And could you imagine using induction in a professional kitchen?
I'm sure that in a domestic environment it suits you well, I can't work with it.

orrery

Richmc said:

"I also query whether gas is always best" - Ask any chef.

That's just out of date. An induction hob is just as fast and is much more controllable than gas. And way, way cleaner.