Last year Martin and Debra Myhill invested in solar panels for free energy! Read on to find out why they took the plunge, and how it’s worked out for them. A year ago we used the Devon County Council scheme to install 16 solar panels, a 5.2KWh battery and 5 KWh inverter. Already I can see your eyes glaze over but welcome to the wonderful world of solar electricity. Our main driver was to reduce our carbon footprint and consume less grid energy. Financially, it’s a considerable investment –– anywhere between £6000–£8000. Energy savings and export payments typically pay this back in around 10 years, though given the recent energy price hikes, ours might do so somewhat earlier. Those who have visited us will know that we have a large house. It has a 10 year old eco gas boiler, 16 original radiators, an extremely efficient wood burner, and everything else runs on electricity. Our house was built in 1987 and is timber–framed which provides considerable insulation. Although there are clear energy spikes when our families visit, mainly it’s Debra and I who consume the energy and, in general, we’ve always been ‘careful’ although not miserly with it (said Debra sitting under a warm throw). The way the system works is relatively simple. The rooftop panels convert energy from the sun into electricity. It doesn’t have to be full sun – even rainy days generate some power. A clever box called an inverter manages the electricity so that it’s converted into alternating current suitable for the electricity network in the house and also prioritises it for our consumption, battery charging and/or export to the National Grid. The battery cuts in when the inverter asks it to provide or boost electricity available in the house. It can charge very quickly (often within 30 minutes). Excess electricity is sold to the National Grid. Clearly the concept of ‘free’ energy consumption is a myth. Although we had some problems with our system during the winter, eventually fixed remotely (from China!), we do have a full and extensive set of data covering our ‘before and after’ consumption, in as much as any two years are comparable.

  • Financially we saved around 50% of our gas and electricity bills
  • The panels provided 65% of our electricity and 35% of our total energy use (despite largely being out of action between December and February)
  • A quarter of our own ‘panel’ consumption came from our battery system (i.e. during the night when there’s no panel output but appliances still operate, and to boost lower panel power in early mornings and later evenings).
  • We exported nearly 50% of our electricity to the National Grid.
  • Some considerations:
  • Given ready access to a panel phone app and smart meters, it is easy to become obsessive about energy use. Debra (eyes rolled) will tell you that conversations regularly commence with ‘we’re generating 5KWh of electricity’. Actually, careful monitoring of data can be extremely productive (that’s my excuse). It does pay to know a little about KWh (kilowatt hours) and have awareness of your own energy use and costs.
  • All systems have a capacity. Our main shower uses 9 KWh and our inverter limit is 5 KWh so the shower will always draw from the national grid. In that case it helps to keep usage brief and, where possible, during sunnier parts of the day. However, everything else (kettle, washing machine etc.) uses no more than 3 KWh. It pays to use these efficiently (e.g. full washing loads) and to stagger their use rather than run everything at the same time.
  • During the sunnier months we heat water from our panels, boosted occasionally in the early mornings by our gas boiler. We installed a timer to maximise use of ‘spare’ electricity based on consumption patterns but you can buy a device to do this automatically.
  • The Smart Export Guarantee payment is absolutely derisory. It is government policy to open this up to market forces but basically that means energy companies pay as little as they can get away with. Like many things, you can shop around but there are often strings attached. One of the best deals pays around 7p per exported KWh but we get 1.5p per KWh from EDF (noting that I pay 32p per KWh to buy their electricity – or you do, to buy the electricity I generated for them). I am in a direct dialogue with the Energy Minister about this ‘imbalance’ but don’t expect anything to change.
  • We already have well insulated loft space and an eco boiler. However, many of our radiator valves had become inefficient. One of the most significant winter savings has come from replacing those and simply zoning the heat. It’s worth reviewing what you already have.

Perhaps the next most effective step will be to increase the size of our battery so that it provides electricity for longer during dull spells of weather (it copes well anyway for about eight months of the year). After that, it might be that we dispense with gas altogether, although almost total reliance on electricity.