It’s been 1 year since we had the solar PV panels installed on the front roof of our house. It’s been a really inspiring and life-changing experience in many ways and we’re more aware now of how much energy we’re using and what times of day it’s best to use certain energy-intensive appliances.
So, over the year, the panels produced nearly 1250 units of electricity, which will give us around £540 from the feed in tariff (at 43.3p per unit) and equaled 43% of the electricity we used.
The types of fuel we’ve been using are wood, gas and electricity. For gas, there is an equation which the gas companies use to convert the metric units of gas which is burned in the boiler or oven/hob to a KW/h ‘unit’.
units used x calorific value x volume correction / conversion to KWh = gas used in KWh
This is… X units x 39.3 x 1.022640 / 3.6 = X KWh
This allows you to compare the actual energy that is used for gas and electric, in a comparable unit, in this case KWh. This is a bit geeky but the figures below (even for what turns out to be our very low usage) are pretty big, especially when the gas and electric consumption is compared with what our solar panels are generating. Here are our figures for the last year…
(01/01/2011 to 01/01/2012)
Gas = £249.18 or 3371 KWh
Electric = £374.52 or 2923 KWh
(01/02/2011 to 01/02/2012 – our 1st full month generating was February 2011)
Solar panels = £540 (income) or 1248.9 KWh
So, £623.70 spent on gas and electric for the whole year. Add to this the £360 for the 6M3 of firewood for the space heating of the living areas gives £983.70, which is the total spent on fuel/energy for the year.
The total in energy terms (KWh) was 6294 for gas and electric. I’m not sure how to work out the KWh provided by the wood though??
From the cost of £983.70, the income from the solar panels should be deducted (£540), giving a grand total spent on energy for the year of £443.70!
Two really important issues come out of this. The first is the comparison of KWh totals for generated and used, as follows.
Total generated = 1,248.9 KWh
Total consumed = 6,294 KWh
There’s obviously a bid difference there and even with the solar panels, with the consumption roughly 5 times more than the generated (or even more if you add in the unknown energy value for the wood). Solar panel efficiency has got a long way to go before it’s able to claw back some of this difference.
The second thing to highlight is the ‘average’ figures for 3-bed semis, which all the price comparison websites use for their standard figures. These are their figures for consumption per year.
- Average electricity usage of 3,300 kWh for standard single rate electricity that’s averaged across all regions and
- Average gas usage of 20,500 kWh per household
Assuming 8p per KWh unit of gas and 10p per KWh unit of electricity would give…
Gas: £0.08 x 20,500 KWh = £1,640
Electric: £0.10 x 3,300 KWh = £330
Combined total = £1,970
If this total figure is used as a comparison, our total of £443.70 is amazing. This is 22% of the average and i’m proud that all the combined features we’ve installed and the way we live has led to this figure. It makes all the chopping of the fire wood much more appealing!