Starting the load list

So we knew that the most important place to start with the solar system for the house was to work out what our electrical load was going to be, in both summer and winter, and what compromises we were prepared to make to our day to day living.

We use approximately 12 kWhr/day at the moment. We have gas central heating, hot water and cook top, adding significantly to our overall energy usage. We have an evaporative cooling system.

Living without external services means we need to add electrical power to cover off our gas usage potentially, but also to cover the waste water treatment system and water supply pumps.

To develop the load list, we needed to work out how we were going to heat and cool our house, and what the extra services loads were going to be. We also needed to decide what our peak energy usage needed to be to ensure our off-grid equipment was sized appropriately – did we want to boil the kettle, while running the toaster, dishwasher, washing machine and dryer while ironing? This can impact inverter sizing and battery selection.

The heating and cooling seemed like the first thing to sort out, since it has a fundamental impact on house design. New Victorian houses need to be built to a minimum of 6 stars energy rating, and while this is much better than older housing stock, it’s still not great. There’s lots of information around passive house design, and designing for a very high star rating. It’s difficult to do, seems to require specialist builders, and would be exceptionally expensive for a house our size.

We made the simple, relatively low cost decision to improve our energy performance – double glazed windows. We also opted for “light bridge” windows – double glazing incorporating low e glass. This took us to a 7.5 star house without really trying.

Beyond that, we started looking for the most efficient way to heat and cool our house.

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