Storing electricity from solar panels

This is HKDE director Chris Handel’s diary of his own project – a solar battery installation.

“After much deliberation, the exciting day has arrived that should unlock the power of our solar array: a battery storage system is being installed by local firm PDP.

Four medium sized boxed have been opened, to reveal the latest battery technology on offer to householders. Tom our installer is now connecting them up to our power supply.

The system has been carefully matched to our 3 Kw PV array, with 7.2 Kwh of electricity storage which should ensure that for 9 months a year we’re pretty much be running on our solar power alone.

How much electricity can be stored depends on a whole load of factors, but roughly speaking you should be able to at least double the % of PV power you consume in the home (on average from about 25% without storage to 50%). This won’t affect the FIT payments you receive (which assume you use 50% of the power you generate, though most people don’t use that much).

So the battery storage should at least halve the electricity you take from the grid. For example, the average UK household uses 3,600 kWh per year, and if you have solar panels you might get a third of this from your solar panels and pay for c. 2,400 kWh. With a home storage battery this might fall to 1,200 kWh. At 17p per kWh you’d save c. £200 a year.

At current battery prices that’s a long payback of over 10 yrs, but given likely upward trajectory of electricity prices the saving could increase and payback time shorten. Soon power companies will offer us cheaper tariffs for off-peak power: a battery would enable you to draw on this cheaper electricity and avoid paying peak prices. This would reduce your bill and increase savings further.

I’ll post again when we’re up and running with how the system is performing.”

Chris Handel

HKD Energy director