Can putting Solar panels on your house save you money?
Quick answer is YES.
Can they pay back what they cost in a reasonable time?
Well, this isn't as straight forward. This depends on how much energy you use and how much cost per unit it is. Having a 4kw system on the house it took around 7 years to pay for itself, and energy costs was around 16p per kwH. Things have changed since having the panels installed. Cost of electric is over double what it was. Also any new systems you dont get paid for selling back to the grid(I'll cover this later)
How much can it save?
The 4kw system on the house generated around 3600kWh over the year. Say if our energy costs is 48p per unit, that 'could' save you £1728 per year. The reason I say 'could' is if you dont use the energy you generate, it is lost. The summer months it can generate over 20kWh in a day, but if you only use 4kWh in a day, then the 16kWh left over is lost(unless you store it). So really you are only saving electric when you are using electric when the sun is out. Ideal to cook the roast dinner while the sun at mud day, as it would be totally free. Often seeing 3kw being generated. So boiling a kettle would be free at that time.
Before solar panels I was using 2200kWh from the grid. After installing panels I was buying in 1200kWh. The house is using power overnight, fridge, things on stand by etc, boiling the kettle when the sun wasn't out. Having a shower is 10kWh for however long you take. So there is plenty of energy being used that solar isn't helping with.
The cost of panels are fairly cheap, around £150 for a 400w panel which is 1mx2m. 10 of these for £1500 gets you 4kw. Then you need an inverter, these are around £1000. You would also need an electrician. So not including electric costs/cable etc, £2500 for a 4kw system that could save you £1728 a year if you are a heavy user of electric 24/7, that pays for itself in under 1.5years
How can we make this better?
Mentioned earlier, if we dont use the electric generated then it is lost. However if you have battery storage you can use everything you generated. The batteries are the really expensive part. £1500 for 5kwh of storage. 4 of these would store a whole day of summers energy. If your house is only using 4kwH a day, then you can run the house for 5 days with no sun. The system would keep itself topped up when ever the sun comes out. Certainly a very good thing to add to the solar system, however the cost is a real draw back. The price I put was for a Lithuim rack mountable battery, has temprature control built in, communications with the inverter. you can actually use a stack of car batteries instead as the inverters can charge lead-acids too.
On new installations this cannot be applied for. However I wanted to pop this in here for completness. Every 1/4 of the year I need to give the solar meter reading to the energy suplier that I signed up for FIT payments with. Over the year I get around £700 back for the energy I have generated. This is from a generation meter, I could have used all that energy and not put any back in the grid, but still get paid the same.