Earth Notes: Saving Electricity and Gas (2020)

Updated 2020-10-02 15:05 GMT.
Meter readings and energy-saving notes for dual fuel use at home in 2020.
gas meter m3 with Loop
2020 PV Output
Meter readings and analysis of our electricity and gas carbon footprint at home in 2020.


See the daily PV generation logs for 2020 as .csv and .png chart.

2020 kWh and HDD

See gas use kWh and heating degree days (HDD) by time for 2020 as .csv and .png chart.

2020 kWh vs HDD regression

See gas kWh vs heating degree days (HDD) regression for 2020 as .png chart.

See 2012 kWh/HDD estimates plus recent years' estimates from daily Loop data and HDD, with the linear regression fitting in gnuplot itself(!):

Estimates of heating efficiency by year, 2007 to 2012 and 2016 to 2020
YearBaseline (kWh/d)Slope ((kWh/d)/(HDD12/d))year kWhyear HDD12
2020p4.81.7(Note: Jan--Jun data only, lockdown from March, record sunny spring!)

Basic heating efficiency (kWh/HDD) has remained fairly stable at ~2.4kW/HDD since the Loop gas meter went in in 2016. Baseline gas consumption, only DHW since May 2013, is hovering around 3kWh/d, according to this computation. Both figures are reasonably true to life, I think, though gas consumption kWh/d data is very noisy for example.

2020 is an odd year starting with record spring sunshine and warmth, and the coronavirus lockdown from March pushing up occupancy and likely gas (eg for DHW) and electricity use (eg for baking, TV and Xbox).

2020-10-02: Price Freeze

As of October, Ecotricity emailed to say that prices are frozen for a year. Each of gas and electricity have a standing charge of a little over £100 per year. The unit (kWh) price is 20.79p for electricity and 4.8825p for gas, a ratio of 4.3:1. Using a heat-pump with a (S)CoP at least this would keep OPEX for space heating and DHW no higher than gas. For space heat this is plausible with a lowish rad flow temperature (eg 35°C), and a ground-source heat pump. For DHW that CoP at (say) 55°C would be hard, but eased if half the DHW was in fact provided by solar PV diversion, ie outside winter months. Our projected annual bills are ~£240 for gas (~3MWh) and ~£270 for electricity (~800kWh). Note that the standing charge is nearly half of each.

2020 Fuel Consumption Data
MonthConsumed kWh (/d)Generated -kWh (/d)Consumed kWh (/d) PeriodNotes
2020-01 230 (7.4/d) -63 (-2.0/d) 487 (16/d) 20191231T18:17Z to 20200131T18:15Z (31d) Meter readings: electricity generation 63.4kWh, export 13.1kWh, import 180.3kWh (thus net consumption (I+G-E) 230.6kWh, self consumption ((N-I)/N) 22%); gas ~43.7m^3 (so 487kWh @ 11.1kWh/m^3).
Unusually high electricity consumption possibly in part from extra use of dehumidifier in kids' bedrooms (which could really do with their own MHRV).
HDD12=142 vs 218 last January. (Warmest Jan since 2008.)
2020-02 197 (6.8/d) -127 (-4.4/d) 434 (15/d) 20200131T18:15Z to 20200229T18:15Z (29d) Meter readings: electricity generation 129.9kWh, export 49.9kWh, import 120.1kWh (thus net consumption (I+G-E) 197.1kWh, self consumption ((N-I)/N) 39%); gas ~39.1m^3 (so 434kWh @ 11.1kWh/m^3).
High electricity consumption possibly in part from extra use of dehumidifier in kids' bedrooms again.
HDD12=128 vs 132 last February. (Warmest Feb since 2008 barring 2014.)
2020-03 213 (6.9/d) -337 (-11/d) 359 (12/d) 20200229T18:15Z to 20200331T17:50Z (31d) Meter readings: electricity generation 337.3kWh, export 209.1kWh, import 85.2kWh (thus net consumption (I+G-E) 213.4kWh, self consumption ((N-I)/N) 60%); gas ~32.3m^3 (so 358.52 @ 11.1kWh/m^3).
Decent sunshine and thus solar gain on some days has reduced space-heat demand.
A lockdown for coronavirus started formally on the 23rd, meaning that all four of us are at home all the time other than Jean's lunchtime gig at school, and the odd walk. (Note that we had partial lockdown for a little before that as I was self-isolating and then the family had to stay in for a few days too, as rules changed.)
Being at home all day means possibly slightly more able to manually match electrical loads (eg the dishwasher) to PV generation, thus increasing self-consumption a tad. (53% last March to 60% this.)
PV generation is up a bit from March last year (9.1kWh/d to 11kWh/d).
If the heat battery project had been done, I'd basically expect gas demand to stop until September or later.
The Loop electricity monitor seems to have died on the 22nd.
HDD12=142 vs 89 last March.
2020-04 218 (7.3/d) -536 (-18/d) 171 (5.7/d) 20200331T17:50Z to 20200430T15:22Z (30d) Meter readings: electricity generation 536.0kWh, export 365.3kWh, import 49.9kWh (thus net consumption (I+G-E) 217.6kWh, self consumption ((N-I)/N) 77%); gas ~15.4m^3 (so 170.61kWh @ 11.1kWh/m^3).
Turned central heating off 2020-04-01T09:43Z; house occasionally a bit chilly!
Gross consumption of electricity is still on the high side, possibly from everyone being at home, and some extra baking, use of TV and games console and other electronics, etc.
Self-consumption is up from 69% to 77%; better manual load-timing opportunities and record sunshine/generation.
Record PV generation of 18kWh/d: cf last April's typical 15kWh/d. 17kWh/d has been seen twice in April. (April 2020 provisionally sunniest on record for UK.)
Gas is unusually high too, which could just be from extra DHW use.
Loop sent a replacement electricity monitor, back in service on 24th. Thanks!
HDD12=61 vs 89 last April (yes, same as March!).
2020-05 217 (7.0/d) -743 (-24/d) 163 (5.2/d) 20200430T15:22Z to 20200531T17:25Z (31d) Meter readings: electricity generation 743.2kWh, export 557.1kWh, import 30.7kWh (thus net consumption (I+G-E) 216.8kWh, self consumption ((N-I)/N) 86%); gas ~14.7m^3 (so 163.39kWh @ 11.1kWh/m^3).
Gross consumption of electricity is still on the high side, probably from everyone being at home under lockdown as for April.
Self-consumption is up from 75% to 86%; better manual load-timing opportunities and record sunshine/generation.
Record PV generation of 24kWh/d: cf last May's typical 18kWh/d in line with the original PVGIS prediction. (Historic kWh/d in May up to 2019, max 21: ... 17, 17, 19, 19, 17, 21, 18.)
Given that the import supply meter indicates very nearly 1kWh/d, the Enphase may be consistently somewhat overestimating avoided imports. (For example, the import meter shows 31kWh this month, Enphase 16kWh.) This is complicated by the fact that the import and export meters themselves may consume ~1W each or up to 50Wh/d, though I've put the Enphase supply clamp upstream of them to try to cover their consumption too (whether or not ethically I should have to!) so as to minimise all grid flows.
This month PV generation passed 33MWh on the first 3/4s of the system, and 10MWh on the remaining 1/4.
HDD12=31 vs 39 last May.
2020-06 196 (6.5/d) -576 (-19/d) 145 (4.8/d) 20200531T17:25Z to 20200630T16:51Z (30d) Meter readings: electricity generation 576.2kWh, export 416.4kWh, import 36.0kWh (thus net consumption (I+G-E) 195.8kWh, self consumption ((N-I)/N) 82%); gas ~13.0m^3 (so 144.74kWh @ 11.1kWh/m^3).
Gross consumption of electricity and gas are still on the high side, probably from everyone being at home under lockdown as for April and May.
Our 'stuck' sunshine weather pattern is gone, so no PV records.
HDD12=4 vs 4 last June.
2020-07 189 (6.1/d) -568 (-18/d) 125 (4.0/d) 20200630T16:51Z to 20200731T17:42Z (31d) Meter readings: electricity generation 568.3kWh, export 417.9kWh, import 39.0kWh (thus net consumption (I+G-E) 189.4kWh, self consumption ((N-I)/N) 79%); gas ~11.3m^3 (so 125.43kWh @ 11.1kWh/m^3).
HDD12=2 vs 0 last July.
2020-08 151 (4.9/d) -464 (-15/d) 76 (2.5/d) 20200731T17:42Z to 20200831T17:19Z (31d) Meter readings: electricity generation 464.4kWh, export 343.3kWh, import 28.5kWh (thus net consumption (I+G-E) 150.6kWh, self consumption ((N-I)/N) 81%); gas ~6.9m^3 (so 76.48kWh @ 11.1kWh/m^3).
Only one week away from home on holiday this August, so dips in daily consumption less dramatic than usual.
Residual electricity consumption when away same as last year. (No imports at all while away (<0.1kWh) according to the supply meter.) ~1.8kWh/d of which ~1.1 fridge/freezer, remainder networking (~10W?), security lighting and monitoring/control equipment such as Enphase.
HDD12=1 vs 0 last August.
2020-09 157 (5.2/d) -376 (-13/d) 119 (4.0/d) 20200831T17:19Z to 20200930T17:16Z (30d) Meter readings: electricity generation 376.3kWh, export 288.1kWh, import 68.7kWh (thus net consumption (I+G-E) 156.9kWh, self consumption ((N-I)/N) 56%); gas ~10.7m^3 (so 119.21kWh @ 11.1kWh/m^3).
This shoulder month would probably benefit from an expanded Enphase battery, increasing self-consumption markedly.
HDD12=12 vs 6 last September.
~1347 words.