Sunday, December 13, 2009

Install Gas/Oil or use Night Rate for underfloor heating?My cold damp house is

My stone and earth, cold, damp house is heated by two wood (and occasionally a bit of coal) fired stoves. The wood has so far come from felling 40 year old Sitka spruce on the property and I have some willow and other copice trees growing. But unless I keep both fires going full pace all day, most of the house sticks at 5 degrees C through the winter. Miserable. I have underfloor heating installed, but rarely have enough hot water for it to make a difference and the cost of running the 12KW of immersions in the water tank is high.

Having been purist about using only wood for the first 7 winters, I gave in and started putting the odd bucket of coal in the stove and I have to say it makes a HUGE difference. Even one bucket of coal a day gives enough extra heat for the UFH to kick in a bit and at least one room is positively warm for most of the day. Having looked at the cost of installing more biomass solutions - a ceramic stove or gasification boiler, both costing over €10k, and the extra work and wood required, I've also had to consider gas or oil at an installation cost of only 2-3k.

But what I have been holding out for is real time pricing. The electricity companies buy from a pool supplied by the generators. When it's windy that price is low because wind companies can sell at whatever price they can get, their costs are the same if they sell or don't. If it's a still cold afternoon in winter, the price can be very high as extra gas fired power stations are fired up. So the electricity companies buy at variable prices and sell to us at fixed prices. I want to buy my electricity at a fixed premium above the pool price, so when it's windy I get cheap electricity and can turn on my UFH at a couple of cents and hour and when it's not, I put an extra few logs on the fire. You can read more about Real Time Pricing at Jerry Sweeney's blog at, it's coming but we need smart metering etc.........

So in the meantime, should I bow to pressure to get a programmable fossil fuel solution to my heat problem, get some heated fingerless gloves or use night rate electricity? I've experimented with turning on the immersions during the night - the UFH kicks in automatically when the water reaches a certain temperature. By using 60kw a night at a cost of €5.22, I can rise the temperature of the whole house from 5 to 10 degrees and the rooms with the stoves in maintain a toasty 12 degrees overnight. A huge difference in the quality of life of the inmates.

Here is the cost calculation:

Price of Night Rate Electric kw


Price of Gas per kw


Units per night


Cost per night electric


Cost per night gas


Gas saving/night


Installation of Gas boiler/tank


Worst case - 200 nights/year


Payback period years


Ignoring maintenance costs for the gas/oil boiler and assuming the ratio between electricity price and gas/oil price remains unchanged, 4.7 years before I'm saving by putting in another solution! And my bet is that electricity will become, relatively, cheaper as we increase the proportion of wind. And Once the real time pricing kicks in, I could be heating the house for €1 a night on renewables and helping to balance the load on the grid. Then I would be smug and snug!


Nathaniel said...

Great Info!!!

nuheat said...

I think everybody in the season is having the same problem of under floor heating. I have using nuheat’s under floor heating tiles. I suggest it to everybody.

Phoebe Bright said...

My original hot water system was from nuheat - nearly 10 years old now and I'd happily recommend the company - good service and good product.

swae said...

Under floor heating systems may be an excellent source of heating a home but if you already have a fuel efficient source of heating your home, you may still find a way to use an under floor heating system. Suntouch floor warming keeps the warm home for you in winter.