Saturday 23 March 2013

The first year of Solar

We have today arrived at our solar panels' anniversary. so here are the figures:

2605.87 kWh (as read on the sunny beam yesterday) although Mike would like me to add half of the 22nd of this year as we got the meter turned on at lunchtime on 22nd last year! This makes the absolute total for the year 2607.14 kWh. Our meter for sending readings to the electricity board is only reading 2591 kWh, I am therefore going to round to 2600 anyway for all the rest of the calculations.

The original estimated generation figure given to us by Hereward Solar was 2190 kWh for the year so we have far surpassed that :) Mike then used an estimating site to generate some monthly amounts - he thinks it was the European Commission Joint Research Centre of the Institute for Environmental Sustainability, Renewable Energies Unit so we then plugged these into pvoutput.org and are using these to see if we are running to target.



Month
Estimate
Actual
Above or Below estimate
April ’12
261
255
below
May
305
328
above
June
295
301
above
July
311
336
above
August
284
326
above
September
226
278
above
October
171
181
above
November
101
104
above
December
63
75
above
January '13
89
68
below
February
129
123
below
March
195
93 in 2012
above total for both part months


116 in 2013
likely to be below for rest of March




Total
2430
2607




so we have surpassed their estimates as well :)

The more techie toys and monitoring ability Mike gets for me, the more OCD I get about looking at trends, and we started using pvoutput.org to graph our usage as well as our generation in December. So I worked out what we use as a baseline amount over the day. There is an interesting waggle approximately every hour which seems to be the freezer or fridge turning on and off, but basically our low point now is approx 150watts of always on stuff, most of which can be accounted for by the always-on server and hub, router, and WiFi points.

There is an interesting note from one of the points in the office which if you plug a 4-way with a light on it in and leave it on, it seems to use about 30 watts of electricity! - we have turned this off now.
I will put 2 graphs up for the hours from midnight to 6am to show this. The first is from 29/12/12 giving a total usage for 6 hours of 1.73kWh, with a low point of 189W and a high point of 490W:


and the second is from 23/03/13 giving a total usage for 6 hours of 1.46kWh with a low point of 153W and a high point of 450W:


so using a calculation of 1.5kWh for 6 hours, this makes 6kWh for 24 hours or the whole day, assuming we are not in and therefore no kettles, washing machines or televisions are being used.

Given a reasonable sunny day in March - well we did have ONE this year ;) - we can get levels above 400W from 8am till 5pm or 9 hours saving us 2.25kWh during daylight. If I can also arrange for washing machines and tumble driers to be matched up with the really sunny times then I can reasonably ensure free electricity for these items as well, but it does take guesswork and sometimes I am not so good at that, or the weatherman is not specific enough. Now a simple money note is that 1 watt always on is £1 per year and 1kWh costs 12.5p to buy so we were spending 75p per day on baseline or £275 per year, now we have saved 28p per day that it is sunny enough - say 300 days per year or £85 just on having sunshine. 

We appear to have used 3864 units of electricity in 1 year to today. and the year before we used 5708 so all our (my) OCD turning off of unnecessary power/lights etc PLUS the solar has saved us 1415 units or £177 assuming direct translation from units read on the meter into kWh charged on our bill. 

5 comments:

  1. at £177 per year, how long would it take you to pay for the installation?

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    Replies
    1. It isn't £177 a year, though. There's also, if you check Anne's previous post, about 800 a year in Feed in Tariff. Which makes the answer 'about 8 years'.

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  2. A good day in June will get us above maintenance levels for 12 hours making 3kWh saving in the sunshine or 37.5p per day
    Of course this is not the point of having solar -it is for the karma after all, but the savings do help.

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  3. Very cool summary! I'm very pleased for you with how well this is working! *hugs* :)

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  4. Very cool. And by the way, "how long to pay for it" might be the wrong question. We went geothermal a few years back and whenever anybody asks me that question, I tell them "zero". We took out a loan to pay for the system, and the payments on the loan are less (by a couple of hundred dollars a month) than the cost of running the old system. So the system is cash-flow positive from day one (and will be more positive when the loan is paid off). There's really no downside at all.

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