Estimating energy savingd from insulation

oldwiring

Have just had cavity wall insulation put in and an additional 8" of loft insulation. House is already double glazed. Annual energy used
Gas 18350kwh Elec 3455. CH is gas. Oven elec with gas hob. Elec mainly for lighting and occasional heater in smal conservatory, where sometimes we eat lunch even in winter.

What should I use as a best guesstimate of potential energy consumption reduction?

mech_2

A 3500kWh to 4500kWh reduction in gas usage perhaps?

The Energy Saving Trust has some information on savings from insulation, but their figures rarely agree from one page of their website to the next and they don't tell you how they arrive at them, so it's all a bit of a guessing game really.

http://www.energysavingtrust.org.uk/

oldwiring

Used their costs to work out supposed kWh reduction at the price they used. It seems unrealistically high, but then they use those magic words "up to". Those two little words are so loved by salesmen or folk on a mission:rolleyes:

mech_2

Yeah, their figures are all in pounds which isn't helpful as they don't say what size of gas bill they assume you started with.

If I assume cavity wall insulation makes a saving of 15% and saves £120 using a price of 3.06p per kWh (all from their website), then they're assuming a gas consumption of 26,143kWh which is well above average. In fact it would still be above average after the savings, so I think it's a bit on the optimistic side. The same probably applies for the loft insulation.

lu_lu_2

If you have already switched your CH on and you are running it on a time clock take a meter reading now & again in a months time compare the usage to the same period last year and you will see what the KW reduction is you can then calculate your bill & cost reduction.