4. Energy from renewables

The overall contribution of renewables (for instance Photovoltaic (PV) panels) to energy savings is dependent on many factors but in our climate a significant issue is that supply and demand are not well matched.

Solar energy is often most plentiful at times when it is least needed in the home. Around 75% of electricity generated by the solar PV system occurs between April and September. Whereas most heating systems are on between the beginning of October and the end of March. Taken as an average over a whole year a PV system might generate as much energy as is needed by the home but the excess in the summer cannot be used at the time and has to be exported to the grid. The price that a consumer will get for exported energy is less than 25% of the price that it costs to purchase imported energy.

In the past there has been some miss-selling of the financial benefits of renewable energy systems and pay-back periods and economics are further clouded by ‘feed-in’ tariffs and subsidy schemes which credit the consumer for all energy produced regardless of whether it is used in the home. Although these incentive schemes have helped the uptake of renewables, they have generally been funded by increases in the cost of energy for everybody including the less well-off. The various incentive schemes that distorted the pay-back and running costs of renewable systems have largely come to an end. 

The efficiency of panels has increased and their cost has decreased substantially over the last decade. So, providing the maintenance costs and pay-back periods are accurately predicted, this reliable technology has a role. A home with a large hot water cylinder can also make better use of the summer energy by diverting it to the hot water system and supplementing the heat pump, helping somewhat with the seasonal imbalance.

Things that can go wrong:

• Consumer expectations not fulfilled;
• Mistrust of non-certified renewables installers; 
• Running and maintenance costs not fully explained (inverter replacement, pay-back period etc);
• Consumer backlash and delayed up-take.

Future-proofing recommendations:

• DESIGN: Systems designed for specific house types and orientations – it is good practice to follow Microgeneration Certification Scheme (MCS) design standards even though these have been devised for retrofit;
• INSTALL: Avoid product substitutions and deviations from the design;
• COMMISSION: Commission all components and the completed system;
• MAINTAIN: Provide supporting information with the home - BREL guide to promote an understanding of home energy usage including daily and seasonal ‘load shifting’.