Should I go off-grid?

HertsLad

Here is info from the EON quote I received last year. I have now asked them to update the quote, without a battery.
I have removed battery data from the text copied here.

12 x 330 W panels giving a system size of 3.96 kW,

Tier 1 330W all-black panel

Your Energise solution is predicted to generate 3,659 kWh in the first year, saving 845 kg of carbon dioxide and enabling you to become 72.2% energy independent.

Installed Capacity 3.96 kWp

Orientation (degrees from South) -44°

Inclination (angle of the roof) 29°

Postcode Region 1

Yield Factor (kWh/kWp) 924

Shade Factor 1.00

Estimated Annual Output 3,659 kWh

Benefits in Year 1: £368.24

Energy independence: 72.21%

I don't know where the £368.24 for year 1 benefits comes from. As it was a battery based system (8.2kWh), I'm not sure they were assuming any feedback to the grid. But if it's a meaningful figure, the payback period is far too long. My so-called energy independence will presumably fall if I don't have a battery fitted. If they send a revised quote, I will be interested to read it.

HertsLad

matelodave said:

Bear in mind that you have to generate enough power during the day to not only supply your daily needs but also to replensih what you've used overnight from the batteries. You only need a day or two of minimal sunshine and you will deplete the batteries but also have no energy available for your daily consumption. 

3kwh at 240v = 12.5amps which translates to 150a/h at 12v or 75a/h at 24v. As lead acid batteries shouldn't be discharged below around 50% you'd need so store at least twice as much as you think you'll use plus you need to take into account all the inefficiencies that are involved. 

Running a generator to deliver enough energy to provide for your daily consumption could well be more expensive than paying your daily standing charge - especially now petrol is around £1.50 a litre and diesel even more and it's not the most efficient way to charge batteries unless you are prepared to run it every time you want some leccy.  Would you neighbours be happy with one clattering away for several hours to recharge the batteries - I dont think so.

I also noticed that you were thinking of using propane the cost of which becomes disproportionally expensive as the cylinder size reduces, so you'd need to contemplate 47kg cylinders to make that viable although it might work out cheaper to use a propane powered generator rather than petrol.

It may sound like fun to try and beat the system but TBH the cost and hassle probably outweighs any advantage that you might gain from not paying the standing charge.

You make some very good points and have correctly realised that I am having fun trying to beat the system.

You calculate I need 75ah at 24v. So in ball park terms, leaving out inefficiencies, that's presumably what my first two 12v batteries can almost supply, if drained flat (they are 70ah each). But I can only drain them to 50% and that's where the second pair of batteries come in, wired in parallel to the first pair. In drawing 70ah or 75ah from the array of 4 batteries, they will all be around 50% flat. If so, it is not far out. And it gets 'better' because this first array of batteries will only supply half the needs of the house. So they don't need to supply 75a/h but only 37.5ah. As a result, the first array of batteries will be only (roughly) 25% flat.

Is my thinking correct, or am I missing a trick?

I bought a 47kg cylinder of propane when the price was £89. I fear a refill will be far more expensive so am looking into the possibility of using LPG from a filling station. Is there a risk of prosecution or is it only fuel station regulations, one has to worry about?

QrizB

HertsLad said:

I bought a 47kg cylinder of propane when the price was £89. I fear a refill will be far more expensive so am looking into the possibility of using LPG from a filling station. Is there a risk of prosecution or is it only fuel station regulations, one has to worry about?

I've got a small refillable propane bottle. As far as I know it's not illegal to fill them and fuel stations are usually OK but sometimes you'll get someone who is paying attention and doesn't like you doing it.

Hopefully the £89 included the initial hire charge, as a refill should be about £65 to £70?

Do bear in mind that a litre of LPG (as sold for motor fuel) is only half a kilogram. Your 47kg bottle contains about 95 litres of LPG, and at £65 for a refill you're paying around 68p/litre.

theoretica

I have a friend who lives off grid with no power nearby - it does not save them money!  They have a gas powered fridge, something you might want to add to your consideration.  I believe there is risk of prosecution if you refill the wrong type of gas bottle at filling stations, but there are special bottles sold intended for this with built in failsafes - you might want to talk to the filling stations first to explain matters or check they are on a refill list.

HertsLad

QrizB said:

Hopefully the £89 included the initial hire charge, as a refill should be about £65 to £70?...Your 47kg bottle contains about 95 litres of LPG, and at £65 for a refill you're paying around 68p/litre.

I fear Flogas may have been expensive, then, at £89. First, I had to buy an empty 47kg cylinder on eBay, so they could exchange it for the full cylinder. Where can one buy refills for £65? And do you mean taking the cylinder somewhere for them to top up? Or exchanging the cylinder?

HertsLad

Verdigris said:

As they say in the army, "any fool can be uncomfortable".

A key group, some of whom I hoped to reach, are in a group suffering 'Fuel Poverty'. Would you make that comment to them? I suggest they are not foolish but more likely lacking the information on what they could wear to be warmer and more comfortable. And second the awareness of where one can purchase these garments at quite low prices.

QrizB

HertsLad said:

QrizB said:

Hopefully the £89 included the initial hire charge, as a refill should be about £65 to £70?...Your 47kg bottle contains about 95 litres of LPG, and at £65 for a refill you're paying around 68p/litre.

I fear Flogas may have been expensive, then, at £89. First, I had to buy an empty 47kg cylinder on eBay, so they could exchange it for the full cylinder. Where can one buy refills for £65? And do you mean taking the cylinder somewhere for them to top up? Or exchanging the cylinder?

A quick Google shows:

• Flogas refills for £80 (London or Scotland)
• Flogas refills for £70 (Essex)
• Harris Gas refills £65 (Lancashire)
• Calor Gas refills £58 (Cambridgeshire)

I haven't phoned any of these people so I'm going by their published prices.

Verdigris

I was responding to RR's remark about possibly making your house an unattractive proposition to potential purchasers. Saving £140 a year from not having standing charges might not look like good financial sense if the value of the property is substantially reduced.

As I said before, the standing charge is remarkable value for money, if you use it to best advantage by having a smart meter to take advantage TOU tariffs and make best use of self-generated power. You are also more likely to be comfortable.

HertsLad

Verdigris said:

I was responding to RR's remark about possibly making your house an unattractive proposition to potential purchasers. Saving £140 a year from not having standing charges might not look like good financial sense if the value of the property is substantially reduced.

As I said before, the standing charge is remarkable value for money, if you use it to best advantage by having a smart meter to take advantage TOU tariffs and make best use of self-generated power. You are also more likely to be comfortable.

I'm really sorry for thinking your comment was made on the thread for living without heating. I would not have made my comment if I had realised. I wish I could delete it but I don't think MSE allows any editing. For such a leading forum, it's poor. Are there moderators one can ask to make changes like that? 

I agree it's a bit of a risk in terms of the house value and saleability. But I could not be more comfortable than I am at present so there's no improvement to be made there!

Verdigris

Don't worry. I'm not mortally wounded!