iMeasure used the 2007 emission factor guidance from DEFRA: gas is 0.206kgCO2/kWh and electricity is 0.523kgCO2/kWh (5-year rolling average).
2009 | Electricity | Gas | |||
---|---|---|---|---|---|
Month | Consumed kWh (/d) | Generated -kWh (/d) | Consumed kWh (/d) | Period | Notes |
2009-01 | 214 (6.9/d) | -23 (-0.75/d) | 1285 (41/d) | 20081231T18:09Z to 20090131T18:05Z (31d) | Import meter unratcheted, so reading of ~191kWh shown with ~23kWh of the PV generation added back on. HDD12=266 vs 140 last January (temperatures ~1.5°C lower) but ~10% less heating/gas demand, so roughly doubled heating efficiency. Heating is now set to come on for about two 15-minute slots during the night if the house temperature drops below ~15°C since our little one's thermoregulation still needs some help: this keeps the night-time temperature more stable than it might otherwise be on very cold nights. That's somewhat less than we have had in the previous couple of months, and it does not seem to increase gas consumption enormously. This is a frugal form of 'setback' temperature. I note that we used exactly the same amount of electricity as last January, so an efficient fridge seems to have exactly compensated for a newborn! |
2009-02 | 178 (6.3/d) | -73 (-2.6/d) | 1046 (37/d) | 20090131T18:05Z to 20090228T18:03Z (28d) | Import meter unratcheted, so reading of ~105kWh shown with ~73kWh of the PV generation added back on. PV system expanded (tripled in size) early this month, nominally making us net exporters/generators over the course of a year. HDD12=203 vs 172 last February, but much less gas used. |
2009-03 | 177 (5.7/d) | -254.5 (-8.2/d) | 778 (25/d) | 20090228T18:03Z to 20090331T16:40Z (31d) | Import meter unratcheted, so reading of -77kWh shown with ~255kWh of the PV generation added back on. Upgraded to more efficient washer/dryer that can wash in cold/unheated water which may thus save us ~0.5kWh/day depending on laundry soiling/mix. HDD12=140 vs 157 last March, but disproportionately less gas used. |
2009-04 | 149 (5.0/d) | -356 (-11.9/d) | 265 (8.8/d) | 20090331T16:40Z to 20090430T20:23Z (30d) | Import meter unratcheted, so reading of -207kWh shown with 356kWh of the PV generation added back on. Central heating has been off for most of this (unusually warm) month. HDD12=57 vs 105 last April. |
2009-05 | 147 (4.7/d) | -458 (-14.8/d) | 226 (7.3/d) | 20090430T20:23Z to 20090531T17:33Z (31d) | Import meter unratcheted, so reading of -311kWh shown with 458kWh of the PV generation added back on. HDD12=25 vs 22 last May. |
2009-06 | 130 (4.3/d) | -485 (-16.2/d) | 144 (4.8/d) | 20090531T17:33Z 20090630T18:06Z (30d) | Import meter unratcheted, so reading of ~-356kWh shown with 485kWh of the PV generation added back on. HDD12=8 vs 6 last June. (Adjusting for the 7 days that we were on holiday, with base electricity consumption of 2kWh/d for fridge/freezer and Internet server, daily gross electricity consumption while we were here was 5.0kWh/d and gas 6.3kWh/d, ie down from a baseline of ~8kWh/d gas for cooking/washing last year.) The gas meter was changed to a metric (m^3) model this month, with much finer resolution than before, nominally down to 0.001m^3 but with some effort probably 0.0001m^3 or about 1Wh (at ~11.1kWh/m^3)... |
2009-07 | 163 (5.1/d) | -447 (-14.0/d) | 203 (6.3/d) | 20090630T18:06Z to 20090801T13:26Z (32d) | Import meter unratcheted, so reading of -284kWh shown with 447kWh of the PV generation added back on. HDD12=1 vs 3 last July. Single-glazed front door replaced with double-glazed unit, and internal door fitted between living-room and corridor. (I was not at home for the time-honoured month-end meter-reading ceremony, so there is just short of an extra day's flows, with the extra gas being ~0, electricity consumption ~2kWh, and generation ~7kWh.) I'm not sure why our electricity consumption is apparently up a little, though July was fairly damp and dull. |
2009-08 | 143 (4.8/d) | -374 (-12.5/d) | 166 (5.5/d) | 20090801T13:26Z to 20090831T18:00Z (30d) | Import meter unratcheted, so reading of -231kWh shown with 375kWh of the PV generation added back on. Gas 14.933m^3 (so 165.8kWh @ 11.1kWh/m^3). HDD12=2 vs 1 last August. |
2009-09 | 154 (5.1/d) | -256 (-8.5/d) | 189 (6.5/d) | 20090831T18:00Z to 20090930T17:03Z (30d) | Unratcheted import meter replaced during the month with an import/export meter pair (both initially reading 1.6kWh). We lost about 1kWh of generation while our mains was disconnected, and thus our grid-tie was off-line, while the replacement took place. Up until the meter replacement the old meter reading was -84kWh, and generation was 182kWh, thus making for a net consumption of 99kWh for the month until then. Since the replacement we exported 51.5kWh of the generated 73.3kWh, and imported 33.3kWh, making net consumption 55.1kWh. (That is, net consumption = generation - export + import.) We directly consumed in the house 30% ((gen-exp)/gen) of our PV generation. Or, another way, we avoided importing 40% ((con-imp)/con) of our consumption. Total consumption for the month was 154kWh. Gas 17.031m^3 (so 189kWh @ 11.1kWh/m^3). HDD12=7 vs 11 last September. |
2009-10 | 155 (5.0/d) | -126 (-4.1/d) | 300 (9.7/d) | 20090930T17:03Z to 20091031T17:20Z (31d) | Meter readings: electricity generation 125.9kWh, export 91.4kWh, import 120.2kWh (thus net consumption (I+G-E) 154.7kWh); gas 27.071m^3 (so 300kWh @ 11.1kWh/m^3). Replaced 24x7 Internet laptop/server with entirely off-grid-solar-powered SheevaPlug (@~4W) which I believe has caused mains electricity consumption to drop. HDD12=32 vs 83 last October. (We started using central heating mid-month.) |
2009-11 | 161 (5.4/d) | -61.5 (-2.1/d) | 558 (19/d) | 20091031T17:20Z to 20091130T17:26Z (30d) | Meter readings: electricity generation 61.5kWh, export 36.1kWh, import 135.7kWh (thus net consumption (I+G-E) 161.1kWh); gas 50.245m^3 (so 558kWh @ 11.1kWh/m^3). Battery got very low so SheevaPlug back on mains for some of this wet and windy month. HDD12=78 vs 128 last November (cumulative HDD=812, gas 5160kWh this year; HDD12=828, gas 7689kWh last year). |
2009-12 | 169 (5.5/d) | -42.7 (-1.4/d) | 1043 (34/d) | 20091130T17:26Z to 20091231T18:07Z (31d) | Meter readings: electricity generation 42.7kWh, export 21.0kWh, import 147.4kWh (thus net consumption (I+G-E) 169.1kWh); gas 93.919m^3 (so 1043kWh @ 11.1kWh/m^3). SheevaPlug back on mains for getting on for half of this month. HDD12=250 vs 233 last December. |
2009 total (Jan--Dec) | 1942 (5.3/d) | -2958 (-8.1/d) | 6201 (17/d) | 20081231T18:09Z to 20091231T18:07Z (365d) | Electricity consumption down ~5% on last year, generation up ~3x; now ~50%/1MWh net exporters. Gas consumption down ~30% on last year. HDD12 for the year 1068 (vs 1061 for 2008). |
kgCO2 | 835kg (2.3/d) | -1272kg (-3.5/d) | 1178kg (3.2/d) | ~0.74tCO2 (~2.0kgCO2/d) gas/electricity emissions total for 4 people, based on 0.43kgCO2/kWh for electricity (netted) and 0.19kgCO2/kWh for gas. Note that we have not flown this year again, we still do not own a car and travel almost entirely by (usually-electrified) public transport (we drove ~80 miles in a hire/rental car in 2009). |