This example is based on the requirements of a typical family home where hot water is required to heat seven radiators and supply hot water to taps. During the winter, which we will assume covers half the year (180 days), heating and hot water is required for 8 hours each day. During the summer (180 days) water heating is only required for 1 hour each day.

The heating is on as follows;

Winter: 7-11am & 5-9pm

Summer: 5-6pm

THERMAflow Boiler
The Thermaflow storage boiler range are able to operate on the Scottish Power Economy 2000 tariff which will give 18 hours of constant electricity supply at half price.

This example is based on a 210 litre Thermaflow with an output of 9kW

The shut down periods are:
00:00 - 02:00
08:00 - 10:00
16:30 - 18:30

If the boiler is used at maximum, (heating and hot water), for 180 days a year - consuming 9kW/hr, and used for hot water over 180 days - consuming 3kW/hr, the total annual consumption is 13500kW/hrs.

This is Off-Peak electricity and the rate at 01/01/2007 is 5.5 pence per kW/hr.

Flow type boiler using economy 10 tariff
'Flow' or 'Direct Acting' boilers can only operate on meters that provide 10 hours of Off-Peak electricity per day provided by Scottish Hydro Electric.

This example is based on a 9kW boiler and a 3kW hot water element.

Off-Peak times are:
04:30 - 07:30
13:30 - 16:30
20:30 - 00:30

If the boiler is used at maximum, (heating and hot water), for 180 days a year - consuming 9kW/hr, and used for hot water over 180 days - consuming 3kW/hr, the total annual consumption is 13500kW/hrs.

This will have to be based on 7 hours of On-Peak and 1 hour Off-Peak per day in winter and 1 hour at peak rate per day in summer.The On-Peak rate at 01/01/2007 is 9.1 pence per kW/hr.

As demonstrated above the THERMAflow boiler offers a saving on cost of electricity used of £507 over the first year compared to using the equivalent direct acting boiler based on electricity tariffs available in Scotland May 2007.