So what can you do about it? Some say use all the appliances you can during the day. Sure dishwashers and ironing etc. but how often to you need to run these? A better way is to use the export electricity to heat water. A Heatpump hot water system uses very little power to heat water and store it; in a way the Heatpump hot water tank becomes a big battery, storing the energy that would have been lost to the grid as hot water for you to use when it suits you. Installing a timer on the Heatpump hot water system so that it runs during the day when your PV plant is producing free energy is a logical solution. The Heatpump hot water system runs off a standard power point or 10 amp circuit so nothing special needs to be installed. As the PV plant is sending power into the house the Heatpump hot water system will heat up and store the hot water.
The timer prevents the Heatpump hot water system from turning on during the night keeping it quiet and ready for the next morning’s free energy. You have a big family, or you have gusts staying for the weekend? The timer can be manually operated or adjusted if you need it to run longer. 30-40% of a household’s energy goes to heating water. If you have a gas storage/instant hot water system. OK during the warmer months 80% of you gas bill is hot water during the colder months (if you have gas heating) will be more like 30% averaged out 55% of you gas bill is hot water (without heating 75%)
If you have an “Off peak” electric hot water system which is on average about 12c kWh and will use 16-25kWh per night to heat up. Export electricity is between 6c and 21c kWh and a Heatpump will use 4-6 kWh to heat the same amount. Or in layman’s terms about 25% of the kWh’s used.