PV panels on Penlands houses and others

Suitability of PV on Penlands houses.

Nice steep south facing roof?  Dormer potentially giving shadow problems? It could still work.

The roof is about 11 metres long so with panels 1650mm long you can fit 2 rows of 6 along the unshadowed top. Place one more under each end to make 14 total.

How much power?

14 panels at 330W each makes  a 4.6kWp array producing 4,000+ kW.hrs annually or about £500 worth of electricity. This will easily exceed your annual consumption but that extra power is needed to make the system useful on cloudy days. As the power only comes in daylight you’ll soon acquire the habit of running appliances when the power meter gives you the nod.

Total parts cost about £2,500 (£3,000 fitted?)…. See Bimblesolar.com

The rest of your total energy consumption is gas – about 17,000kW.hrs.

At current prices £500 worth of electrical power is matched by £100 worth of gas. Clearly the value you derive from PV depends on how you use them. A heat pump multiplies up the power by about 3 times so that becomes worth £1,500 of electricity but £300 of gas. Sadly it’s the gas figure that’s relevant because that’s mainly what a heat pump will be defraying. It might seem obvious to charge a car but you can buy late night car charging power from Octopus for 5p making those 4,000 kW.hrs worth only £200. Car charging is not a particularly good use of your power.

4.6kW array

The production curve would be like this

(data 4.6kW array – Gatwick area)

The steep roof angle is good for a winter biased production curve and explains why the main peak is not mid summer.

Fattening out the shoulder months is a good thing.



Augmenting your heating with a mini split – a hot and cold blower thingy completely separate from existing heating system. It is a heat pump.

…. Front hall mounted maybe?

e.g.  Panasonic double head unit (for 2 rooms) chucks out about 5.8Kw but, being a heat pump, consumes about 2kW. The cost is £900 and quite easy to fit as it is already gassed up.

A simpler single unit for half the power is only £510 and would definitely run free almost all day.

Mini splits do air conditioning and dehumidifying too…. Good for the laundry room for sure.

A £200 Solic 200 immersion heater controller can divert any unused energy to your immersion heater. NB Gas heats the water tank cheaply already so electric heating is not a bargain but free is always worth having. SMA are bringing out an inverter that does the same thing but is aimed at electric car charging.

Bottom line     Spend £4,000 and get back about £450 a year but not more than £500.

The utility value is high though with at least 2kW available on most days and the hot water tank often fully charged. In summer there will be a surplus which makes the aircon idea look sensible.

From a financial point of view it’s not exactly a no brainer but it’s not necessarily a bad idea either especially when inflation etc keeps raising energy costs. PV prices will continue to fall so this will make more sense each time you look at it again.

Without the mini-split extras the payback drops to about 6 years if you use all the electricity made.  Grid parity is here.