Cheapest Electric Central Heating?

zbiggy

Desperately need help understanding what are my cheapest options for heating my house. Currently have old night storage heaters and 2 open fires. South facing roof shaded by chimneys so Solar PV not an option. No gas in village and no garden access for oil or LPG or to dig for ground heat pump. Air heat pump is an attractive option apart from the very high initial purchase and installation cost. My heat load has been assessed as 18Kwh though I'm not exactly sure what this means! My gut feel is to keep some storage heaters + overnight immersion heater (5.1p per Kwh) to warm the house and provide hot water in the morning and the have an undersized air heat pump (say (14Kw output) to take over for late afternoon and evening. Gut feel again is to have the pump drive underfloor heating in at least the main living areas. As you can see there is far too much gut feel and not enough hard empirical data! Does anyone know of any standardised benchmarked running cost comparisons that can help me? Specifically:-

1. Running costs of Air Pump(£12k) to Underfloor(£12k) v Radiators (£5k)
2. Running costs of Electric Boiler/Thermal store (£2.5k) to Underfloor v Radiators
3. Night Storage Running costs v the above

Note the numbers in brackets are the approx purchase/install costs.

Help:eek::eek::eek:
3.

albyota

Hi zbiggy, I would be interested to know what size your house is to have been caculated at 18kw heat load, as for running costs, the heat pump is the most cost effective option with under floor heating, but higher capital cost, not sure if your figures are correct though.....£24K for heat pump and UFH? Whichever option you go for, make sure the insulation levels are as good as they can be, same for double glazing.

Running costs for an electric boiler with a thermal store on economy 7....hmm....difficult to gauge, how much room do you have to fit a large thermal store, large enough to provide all the stored overnight cheap rate heating to last all day and night in the winter, without the need to boost with the daytime rate?

Storage heaters...well.....depending on your lifestyle, if they are sized correctly, and the house is well insulated, installation costs are minimal, running costs not too bad. make sure you get a free crystal ball thrown in.

I too am in a village, no gas, used to be on oil, got rid of that, and now my 200 M2 house has the 8.5kW Air source heat pump connected to UFH to both floors, and provides all our heating and domestic hot water for family of four, OH & 2 x teenage daughters, including electric cooking, tellys, washing machine 4 x wk, dishwasher everynight, computers, 3 x hairdryers every morning (not me) so all electric house with total annual running costs of £840.

paceinternet

Do be careful with your running cost calcs if you have a system that uses E7 overnight and large amounts of day rate electricity (which is more expensive on E7 tariffs).
You will most likely find it is better to NOT have E7 and benefit from lower day rates. Then you will find storage heating is not cost effective.

As albyota has said, find out what can be done insulation wise to reduce that 18kw.
An air source heat pump solution with some direct electrical heating backup must also be considered instead of trying to size the heat pump to provide all the heat at the lowest winter ambient temperature.
If your property is of a size that requires 2 zones, maybe consider separate solutions so the area used most gets the lowest running cost kit.

zbiggy

Thanks for replies and informative figures. However, it would still be very useful if any one knew of, or could work out a theoretical model that compared different solution running costs on a like for like basis. I know so little about this that I'm struggling to define the assumptions one would have to make but here's a starter: Outside Temp 5 (all temps degrees C), desired House Temp 21 from 6am -10am and 4.00pm - 8.00pm, 100 litres hotwater required in each of these periods )total 200l), Heat Load 15Kwh (does this tell us all we need to know about the property's energy efficiency/insulation?). What other assumptions do we need to make to construct a SIMPLE model?

I'm particularly interested in the running cost of a electric boiler system given the much lower capital cost v Heat Pump. Albyota's points above are well made: is it possible to quantify them? Al, do you know roughly how much water circulates in your system and what the return temperature is after circulating through the underfloor system? If we assumed a 300l tank heated overnight at 5p per KWh, how much energy would we use during the day to maintain adequate CH/Hot Water Temperatures? Sorry if I'm asking the impossible; I'm just hoping there's a boffin out there who could work this out.

(Albyota, all numbers come from a number of quotes from authorised heat pump installers)

albyota

OK zbiggy, lets start from the beginning, what size is the house? how many floors?, is it very well insulated? Why has the heat load gone from 18kW down to 15kW?
why only 5 degrees outside temp....are you in the UK?....try minus 8, Remember February 2010

The total water capacity of my underfloor heating system is about 240 litres, however, only a couple of circuits operate at any one time due to each heating zones actuator valves on the UFH manifolds. Due to the thermal mass, it acts like a large storage heater, the flow temperature is 38 degrees, the return is 28 degrees.

The average hot water requirements are 65 litres/person/day.

" If we assumed a 300l tank heated overnight at 5p per KWh, how much energy would we use during the day to maintain adequate CH/Hot Water Temperatures? "

As for direct electric heating, what temperature is the store going to be heated to? if you can get it to 70 degrees on economy 7, you might stretch it for underfloor heating (40 degrees) for between 6 & 8 hours, I would go for a 600 litre tank with an external domestic hot water heat exchanger arrangement. Two 6 kW elements going full chat for 7 hours at 5p/kWh should just about get there and it is going to cost about £4.20 per night.
Would this heat your house in the depth of the winter????