Economics

MICRO CHP

the big picture

By Jeremy Harrison

IS MICRO CHP WORTH THE MONEY?

Many people interested in micro CHP are unsure whether it is economically worthwhile to install such a system. This simple calculator is intended as a tool for you to calculate your potential energy savings, based on your current fuel bills. From this you can work out how long it will take to pay back the investment in micro CHP.

Please note that this spreadsheet is provided only for you to undertake an estimate and that each home and household is different. You should satisfy yourself that the result is reasonable. You will not be asked for your personal details. If you want more information on the product you have selected, please contact the manufacturer (or other supplier) via the links on the products page.

Download the MS Excel spreadsheet and then enter your details to work out how much you can save.

Clicking on the "calculator" button will take you to a Microsoft Excel spreadsheet. You need to have MS Excel installed to run this calculation.

This calculation assumes that you are considering replacing your boiler (which has reached the end of its useful life) with either a micro CHP unit or a new 88% efficient condensing gas boiler. It is based on replacing the boiler with a WhisperGen micro CHP unit; other products may be evaluated if you know the respective heat and power outputs. You will need to know your gas and electricity costs for a complete year, which you can obtain from your annual energy bills.

Simplified Example

An example of a simplified calculation is shown below for illustration only. It assumes that the system is installed in parallel with the existing power supply and that surplus generation is exported to the grid and any shortfall in requirements is imported from the grid. It is based on the WhisperGen (1.0kWe/7kWt) micro CHP unit in a family home with annual heat demand of 28,000 kWh, all of which is met from the engine (not the auxiliary burner).

It is based on a residential installation in the UK eligible for FiT (Feed in Tariff) payments. Other financial incentives including tax relief, grants and subsidies are available in other regions.

Annual heat demand	28,000	kWh
Running hours	4,000	hours
Electricity generated	4,000	kWh
Own use of generation	67	%
Unit cost of avoided import	15	p/kWh
Value of avoided import	400	£
Unit value of export	5.4	p/kWh
Value of export	72	£
Value of FIT (UK only)	500	£
Total value of generation	972	£
Additional gas consumed (compared with new condensing boiler)	4,000	kWh
Cost of additional gas consumed @4.5p/kWh	180	£
Net saving = £972-180	792	£
Marginal cost of unit	5000	£
Simple payback	6.3	years

Page updated 9th March 2015

MICRO CHP

the big picture

By Jeremy Harrison

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Contact : info@microchap.info

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