what about running your house off a DC supply possibly 4 large car batteries

why ? As in why not store heat as heat and if you want batteries at something closer to the voltage of a solar string so the same inverter can be used?

I can see the advantage of a car battery in a caravan, I have even taken one camping - but only to a site I could drive onto - but for a house there are probably better energy storage schemes.

As I see it freezers and maybe hot water are the only loads that cannot wait for generation to come on line.  Prior to 1935 my grandparents had a house without electricity,  prior to the mid 70s they had no fridge, eventually getting a gas one,  part of the solution is that we need to be less needy.

mapj1 said:

As I see it freezers and maybe hot water are the only loads that cannot wait for generation to come on line.

I am not sure I agree.

If you have a well-insulated house then you need to keep inside structures at a minimum of 12°C to inhibit the development of mildew. Mildew is bad for respiratory health, although Brits have typically ignored the issue. (The presence of mildew in rented accommodation in Germany is sufficient grounds both for reducing rent and for exiting a rental agreement without notice.)

Keeping the inside air temperature at least at 14°C, and keeping air circulating and moderately dry, seems to be sufficient to avoid mildew (bathrooms generally have more such problems than other rooms). 

But human beings consume oxygen and expirate water vapour and CO2, so to keep internal climate livable there needs to be an air filtration and management system - the VAC part of HVAC. Also, you don't want all occupants to succumb to every airborne infectious disease that comes marching through the door, so your VAC may be well-advised to include an enclosed UV-C disinfectant  capability. The house walls are maybe not going to suffer much with regular intermittent cold phases when electricity is not available, but you do need to keep your VAC running.

That entails some kind of internal UPS. 

Just to throw a spanner in the works.

I contemplated buying an Ego inverter that runs off their cordless power tool batteries, then changing the SFCU unit to a plug and socket so if there’s a power cut I can still fire the central heating up.

https://www.ronsmith.co.uk/ego-pad1500e-nexus-escape-150w-power-inverter.html

But my understanding is it won’t work because the flame failure device in my gas boiler completes its electrical circuit through earth and won’t run off that inverter.

So I need to rethink that plan.

We also have a bedroom over an integral single garage, so I looked at the price online of bags of loose fill insulation to put between the floor joists to insulate between the bedroom and unheated garage, that came in around £650 so I had better phone a couple of builders merchants to see if I can get a better price.

However I have just added a blind and a curtain to a window in our porch that’s never been covered, my wife said it’s a bit OTT having both on the same window, but at £35 for the blind plus another £35 for the curtain and £15 for the curtain track I’m sure that the investment of around £85 is a sound one that will soon save that the way things are going with fuel prices.  

I have been experimenting with the settings on the hot water cylinder heated by a old gas boiler.

Earlier this year I replaced the hot water cylinder insulation jacket and I have bought an indoor/outdoor thermometer with a wireless remote temperature sensor that can measure up to 60 degrees that I have pushed under the cylinder jacket near the top of the cylinder.

The thermometer cost me just over a tenner through EBay, it now shows the temperature of the hot water cylinder, also the temperature and humidity level on our coffee table along with the maximum and minimum readings.

Along with this I have the in home display for the Smart meters allowing me to easily monitor the gas used.

I have the hot water set to come on in the morning and evening, two people shower and wash plus some hot water is used in the kitchen but we do have a dishwasher.

On days we both shower in the morning I have cancelled the evening heating period, cost wise it makes no real difference to having the boiler coming on twice when one of us has showered in the morning and the other in the evening. Basically having replaced the the insulation jacket the boiler is topping up the hot water remaining in the cylinder when it comes on twice a day and any saving by cancelling a heating period is lost having to reheat from a lower temperature.

My conclusion is that it’s insulation that makes the savings not fiddling with the time clock settings.

Remember, thermostatic mixer showers have a maximum preset of 38 degrees that you have to manually override.

In the winter I shower at 38 degrees, cooler in the summer, so if the hot water cylinder is a 38 degrees or above the thermostatic mixer is blending hot and cold water to achieve the required temperature, so that 47.6 degrees at lunchtime after one person showered this morning indicates there will be enough hot water for someone to shower this evening without the boiler kicking in again.

So I could now cancel tonight’s heating period, but I’m finding the actual cost saving isn’t significant, the lost heat is in the boiler and pipework rather than the well insulated cylinder.

Andy Millar said:

Can a put in a shout for solar water heating.

You certainly can Andy! We've been thinking of installing solar water heating in our house out in France. We have a huge due south facing roof that is perfect for some pipes.

While we were putting up some of the blockwork we left a black hosepipe on the ground one afternoon and the water that was coming out of it was red hot! It's certainly something we're seriously considering. For our French residence anyways.... 

Sparkingchip  I've recently cancelled my morning water heating period as I'm not always there during the day to use any of the hot water anyway. Mine comes on around 4pm so there's hot water for the evening wash up and shower etc. If I am working from home that day I just leave the washing up until later (I don't own a dishwasher or should I say I do have a dishwasher but it's called having a sink and using hands... ) 

I would love to replace my hot water cylinder with something similar to what we have installed in our French home. We find that we can turn off the element 3 days before we're due to return to the UK and the water is still plenty hot enough after those 3 days for us both to have showers and washing up etc. 

Unfortunately in the tank in my UK home, even though it is both foam insulated and has an additional jacket on it too, the water seems to cool off very quickly. 

I think when it comes to replacing the boiler, it may be Combi time... 

Sparkingchip said:

We also have a bedroom over an integral single garage,

Yes, insulate the floor. I take it you have a wooden floor. You don't say what the m^2 is, but if I guess 20 m^2 then the rock wool needed doesn't come to anything near the price you quoted. 

I have an 80 m^3 room sitting over the cellar. When I had the floor insulated the difference in warmth retention was immediately noticeable, but I didn't measure it.

The most efficient winner overall is insulating between upper floors and roof space. Rule of thumb is 25% savings (that is what more elaborate calculations get, also, +/- a couple per cent). That is almost exactly what I saved in gas kWh's when I had it done.

The easy way is to clear out the roof space and just roll the rock wool out on the floor. That cost me well under €1000 for about 150 m^2 in January 2010 and it saved me that in gas costs that very year.  A couple of years ago, I had the floorboards removed and laid it between the joists, so I could use the roof space for storage again. Probably works just as well, but I don't have the gas bills for enough years yet to confirm that more precisely. 

Effective insulation on any water storage which is 10° or more above ambient is essential (unless you just like burning gas to heat up the world). (Or you could install it in the living room without the insulation, but summers might become unbearable.) Also, swapping out that "old gas boiler" for an energy-efficient one may well save you half the cost or more of gas.

A note to the comments about fiddling with the time controls on the hot water, some older central heating programmers only allow you to set the hot water at the same times as the heating, so over the winter the hot water can be on for many hours a day and the boiler can cycle unnecessarily.

Swapping an old programmer for one that allows different time settings for heating and hot water makes significant savings by reducing excessive  boiler cycling.

I grew up in a house where it wasn't possible to have heating without hot water.  The boiler heated the hot water tank, and the heating system took the heat out of the tank.