Earth Notes: Saving Electricity and Gas (2022)

Updated 2024-02-26.
Meter readings at home. #4kWhDHWClub
2022 PV Output
Meter readings and analysis of our electricity and gas carbon footprint at home in 2022.


See the daily PV generation logs for 2022 as .csv and .png chart.

2022-01: Heat Battery On The Way

A Combimate went in at the end of last year to deal with hard water for the whole house (except the kitchen tap) including the Sunamp heat battery.

At the end of this month a myenergi eddi and hub solar diverter arrived as an early part order from Sunamp.

I'm hoping to get the electrics done very soon, then the Sunamp Thermino and plumbing next month or March.

I started devising some of the control software split, and lashed together the first significant part.

20220205 heatbatterytarget
Heat target % max fill from grid, vs actual grid intensity and top-up limit threshold, for 2022-02-05.

See the heat-battery top-up control live data page.

2022-02: Eddi In

This was the mildest February that I have recorded since/including 2008.

The myenergi eddi solar diverter and other electrics were installed on the 23rd.

I continued to tweak the Thermino top-up algorithm and captured regular (10-minute) logs from the eddi, even though the Thermino is not in yet. That is capturing some interesting data such as mains frequency, and when it's sunny enough that the eddi would divert.

20220228 heatBatTarget
Heat target % max fill from grid, vs actual grid intensity, top-up limit threshold and eddi state, for 2022-02-28.

2022-03: Generation Up, Thermino In

Screenshot 20220306 Enphase Enlighten flows today good balance
2022-03-06 screenshot of Enphase Enlighten showing generation (blue), consumption (orange), import/export (black) and battery (green).

2022-03-09: the Sunamp Thermino was installed today, by ~4pm.

Screenshot 20220312 Enphase Enlighten flows constant small exports after 1pm as Thermino heat battery fills by diversion
2022-03-12 screenshot of Enphase Enlighten with constant low exports from ~1pm as Sunamp Thermino heat battery is filled by diversion.

2022-03-28: Diversion Week

In the 7 days to ~6pm BST today, the Eddi diverted ~28kWh to the Thermino. (One sunny day the Thermino covered two showers and one bath!)

Over that week, we still used ~3.5kWh gas, or ~0.5kWh/d. Normal DHW use is ~4kWh/d, ie 7 or 8 times more. (Last March's daily consumption including space heat is ~15kWh/d.)

2022-04: Storage Works!

May2022 bill graph savings

The diversion stats for April are: heat battery mean kWh/d=4.1 (divert/d=4.0, boost/d=0.1).

This month compared with April last year, gas consumption is down from 5.6kWh/d to 0.38kWh/d, with gross electricity consumption up from 5.6kWh/d to 9.5kWh/d, which initially suggests some direct kWh efficiency savings even with resistive heating.

Our May Ecotricity dual-fuel bill covering to 29th April shows a marked reduction in both electricity and gas per day, which will be due in part to the expanded Enphase and the Thermino. Prices are now 36.85p/kWh for electricity and 8.16p/kWh for gas, with a standing charge of just over 31p/day each.

2022-08: Snapshot

As part of some third-party research, I took an electricity usage snapshot for the first five days of August.

2022-09: Cut and Capped

2022-09-15: Power out

At ~2:40pm: the power went off, but I did not even notice because my laptop was off-grid and the Internet router too. A neighbour came round to see what was going on because her power was out. Preemptive text messages from UK Power Networks (UKPN) explained the cut (emergency works, apparently a cable fault) to 105 properties, with power due back on between 4pm and 5pm. This is only about the third power cut since we moved in, so ~18 years, the previous two being about 30 minutes long as I recall. PV generation reported at 0 at 13:40Z; Enphase, Eddi, Thermino (and its monitoring RPi) all off safely as designed. The power came back on (and PV reported generating) at 15:04Z (~4pm), so out for ~1h24. At least briefly the Eddi saw the Thermino as 'full' even though the Thermino did not actually fill today.

2022-09-17: Capped

Ecotricity announced by email tonight its new prices from 2022-10-01 in the light of government intervention. Including VAT, 1kWh of electricity will rise to 40.74p, and gas 11.6025p. Standing charges will rise for electricity to 42.67p per day, but fall for gas to 28.48p per day.

Our annual bills from 2022-10-01 at these rates are projected to be a little under £400 for electricity and a little over for gas. Billed consumption over the last year was a little under 600kWh and 3000kWh respectively.

2022-09-23: Gasless

The combi was unwell and temporarily switched off as of the 23rd. So we are burning no gas, and are using more electricity to cover the DHW.

202209 heatBatteryInputDailyRecent
Boost (purple) takes over from divert (green) from the 23rd when the gas combi had to be turned off and the days were getting gloomier.

2022-10: Transition

202210 Ecotricity bill savings

October is the key month transition from summer to winter, at least in terms of moving from heat-battery fill from PV diversion to top-up boost from grid.

(Spoiler: almost no diversion and lots of high-wind / low-carbon grid top-up in the first week of November!)

Happily, even with the use of boost, the Ecotricity bill graphic shows slightly reduced electricity imports vs last October, along with hugely reduced gas. Though I'm seeing much less dramatic October-to-October falls than the graph, eg gas down from 4.5kWh/d to 0.9kWh/d! (The heating was not on this October nor last October; gas is all for DHW.) The enhanced Enphase capacity this October will probably have helped. What also happened is that exports more than halved, from 65.8kWh to 28.6kWh. So all grid flows (including gas grid) were reduced, which is generally good.

202210 heatBatteryInputDailyRecent
See PV diversion disappear and boost top-up from low-carbon grid come in.
2022 Fuel Consumption Data
MonthConsumed kWh (/d)Generated -kWh (/d)Consumed kWh (/d) PeriodNotes
2022-01 225 (7.3/d) -66 (-2.1/d) 676 (22/d) 20211231T18:16Z to 20220131T17:20Z (31d) Meter readings: electricity generation 66.2kWh, export 0.9kWh, import 160.0kWh (thus net consumption (I+G-E) 225.3kWh, self consumption ((N-I)/N) 29%); gas ~62.0m^3 (so 676kWh @ 11.1kWh/m^3).
We have had sunny days at the end of the month that have just pushed generation above 1kW and thus beyond the ability of the Enphase to absorb. That allowed a tiny bit of export.
Bathroom MHRV still not repaired — treating as an experiment.
The Enphase emailed monthly report for January (received 2022-02-12) says: produced (generated) 67.0kWh (max 5.3kWh on the 31st), consumed 208.8kWh (max 8.5kWh on the 10th), grid energy imported 157.9kWh and exported 0.5kWh, energy independence 24% (max 56% on the 30th).
HDD12=204 vs 241 last January.
2022-02 189 (6.7/d) -132 (-4.7/d) 441 (16/d) 20220131T17:20Z to 20220228T17:46Z (28d) Meter readings: electricity generation 132.1kWh, export 17.9kWh, import 74.3kWh (thus net consumption (I+G-E) 188.5kWh, self consumption ((N-I)/N) 60%); gas ~39.7m^3 (so 441kWh @ 11.1kWh/m^3).
The myenergi eddi solar diverter was wired in at the end of the month. and this was running part of the month. But the Thermino heat battery was not there to receive energy, so 0kWh/d electricity used for DHW of which 0kWh diverted and 0kWh boosted.
We have had very sunny days at the end of the month that have filled up the Enphase and allowed some export.
This month had the lowest February HDD12 at 16WW since/including 2008.
Bathroom MHRV still not repaired — treating as an experiment.
The Enphase emailed monthly report for February (received 2022-03-12) says: produced (generated) 132.0kWh (max 11.1kWh on the 27th), consumed 168.2kWh (max 8.6kWh on the 1st), grid energy imported 72.2kWh and exported 16.5kWh, energy independence 57% (max 98% on the 12th).
HDD12=116 vs 171 last February.
2022-03 302 (9.7/d) -313 (-10/d) 160 (5.2/d) 20220228T17:46Z to 20220331T16:24Z (31d) Meter readings: electricity generation 313.4kWh, export 68.3kWh, import 56.4kWh (thus net consumption (I+G-E) 301.5kWh, self consumption ((N-I)/N) 81%); gas ~14.4m^3 (so 160kWh @ 11.1kWh/m^3).
In the light of world affairs (war in Ukraine, rising gas prices, etc), we turned the heating off on the 7th to cut gas use ASAP.
The Sunamp Thermino was installed on the 9th, by ~4pm. There have been a couple of sunny weeks with good diversion (~78kWh), some manual boost to test things at install (~11kWh) and subsequently, and a tiny amount (~5 minutes' worth!) of auto top-up from grid on the 31st! During the sunny weeks, residual gas consumption was ~0.5kWh/d. Electricity gross consumption (though not import) has gone up as gas has gone down.
(According to the eddi, grid exports were ~58kWh and imports ~78kWh.)
The Enphase emailed monthly report for March (received 2022-04-13) says: produced (generated) 315.3kWh (max 17.9kWh on the 26th), consumed 280.6kWh (max 15.8kWh on the 9th — including over 10kWh testing and loading up the Thermino on boost), grid energy imported 52.5kWh and exported 64.4kWh, energy independence 81% (max 99% on the 26th).
HDD12=113 vs 138 last March.
2022-04 286 (9.5/d) -461 (-15/d) 12 (0.38/d) 20220331T16:24Z to 20220430T17:13Z (30d) Meter readings: electricity generation 461.1kWh, export 194.1kWh, import 18.5kWh (thus net consumption (I+G-E) 285.5kWh, self consumption ((N-I)/N) 94%); gas ~1.04m^3 (so 11.5kWh @ 11.1kWh/m^3).
The Thermino has eliminated over 90% of direct local gas burn. Some extra gas will presumably be being burnt for grid generation for electricity that we did not spill to grid or imported for boost. This month diversion (119kWh) and boost (3kWh) supplied essentially all DHW (4.1kWh/d) while reducing gas demand from 5.6kWh/d to 0.38kWh/d! There remains a bit of gas waste (maybe ~50Wh per time) when someone cranks a hot tap to full-on immediately, which forces the combi to fire up, then switch off again seconds later once the Intasol establishes that it can supply DHW direct from the Thermino.
(According to the eddi, grid exports were ~180kWh and imports ~35kWh.)
The Enphase emailed monthly report for April (received 2022-05-12) says: produced (generated) 463.9kWh (max 25.0kWh on the 30th), consumed 269.1kWh (max 14.1kWh on the 15th), grid energy imported 14.2kWh and exported 190.3kWh, energy independence 94% (max 99% on the 3rd).
HDD12=75 vs 141 last April.
2022-05 319 (10/d) -528 (-17/d) 20 (0.66/d) 20220430T17:13Z to 20220531T16:02Z (31d) Meter readings: electricity generation 528.3kWh, export 229.6kWh, import 20.6kWh (thus net consumption (I+G-E) 319.3kWh, self consumption ((N-I)/N) 94%); gas ~1.83m^3 (so 20.3kWh @ 11.1kWh/m^3).
Somehow this seems to be have been a gloomier month, though generation is up. This seems to have pushed up gas use a little, though it is still tiny.
The Enphase emailed monthly report for May (received 2022-06-14) says: produced (generated) 532.0kWh (max 27.7kWh on the 27th), consumed 303.2kWh (max 15.6kWh on the 16th), grid energy imported 16.3kWh and exported 225.8kWh, energy independence 94% (max 99% on the 22nd).
HDD12=14 vs 54 last May.
2022-06 273 (9.1/d) -624 (-21/d) 15 (0.49/d) 20220531T16:02Z to 20220630T16:29Z (30d) Meter readings: electricity generation 623.5kWh, export 361.3kWh, import 10.8kWh (thus net consumption (I+G-E) 273.0kWh, self consumption ((N-I)/N) 96%); gas ~1.33m^3 (so 14.7kWh @ 11.1kWh/m^3).
The Enphase emailed monthly report for June (received 2022-07-13) says: produced (generated) 627.9kWh (max 30.2kWh on the 14th), consumed 258.6kWh (max 14.7kWh on the 7th), grid energy imported 7.8kWh and exported 359.5kWh, energy independence 97% (max 99% on the 11th).
HDD12=3 vs 1 last June.
2022-07 229 (7.4/d) -628 (-20/d) 15 (0.49/d) 20220630T16:29Z to 20220731T17:15Z (31d) Meter readings: electricity generation 627.6kWh, export 405.5kWh, import 7.2kWh (thus net consumption (I+G-E) 229.3kWh, self consumption ((N-I)/N) 97%); gas ~1.37m^3 (so 15.2kWh @ 11.1kWh/m^3).
Passed 40MWh generation on meter 1 (recently passed 12MWh on meter 2).
DHW ~3kWh/d, and was low even before the rest of the family took mini breaks. Record hottest day (19th) and nearby days may have had an effect! Mains inlet water was getting pretty warm (~24°C), (though not quite the hottest that I have recorded here), so reduced 'lift' as well as reduced demand for hot baths/showers in play.
The Enphase emailed monthly report for July (received 2022-08-12) says: produced (generated) 629.3kWh (max 27.7kWh on the 8th), consumed 214.5kWh (max 10.6kWh on the 2nd), grid energy imported 4.4kWh and exported 401.9kWh, energy independence 97% (max 99% on the 3rd).
HDD12=0 vs 0 last July.
2022-08 179 (5.8/d) -542 (-17/d) 17 (0.54/d) 20220731T17:15Z to 20220831T17:15Z (31d) Meter readings: electricity generation 541.6kWh, export 368.8kWh, import 5.7kWh (thus net consumption (I+G-E) 178.5kWh, self consumption ((N-I)/N) 97%); gas ~1.51m^3 (so 16.7kWh @ 11.1kWh/m^3).
Diversion to the Thermino with no actual DHW demand was, according to the eddi, a smidge over 1kWh/d.
Even though for the fortnight that we were away on holiday we used zero gas — I even turned the combi to off — (and imported 0.1kWh of electricity), we still managed to somehow eat up ~10kWh of gas in the last week of this month so averaged a little over 0.5kWh/d! Bah!
After some analysis, the eddi Export Margin was raised significantly so as to be more grid-friendly.
The Enphase emailed monthly report for August (received 2022-09-14) says: produced (generated) 554.2kWh (max 24.9kWh on the 6th), consumed 162.7kWh (max 11.2kWh on the 26th), grid energy imported 4.2kWh and exported 368.1kWh, energy independence 97% (max 99% on the 11th).
HDD12=0 vs 0 last August.
2022-09 256 (8.5/d) -306 (-10/d) 31 (1.0/d) 20220831T17:15Z to 20220930T17:15Z (30d) Meter readings: electricity generation 306.4kWh, export 82.8kWh, import 32.5kWh (thus net consumption (I+G-E) 256.1kWh, self consumption ((N-I)/N) 87%); gas ~2.83m^3 (so 31.4kWh @ 11.1kWh/m^3).
Generation is dropping fast, and on the 30th for the first time in a while the Enphase did not fully charge and had nearly fully discharged.
Our combi's expansion vessel was failing so on the 23rd we had that fixed with the intention of keeping the combi going until we leave. (There was some gas used while testing the DHW and radiator circuit.) But then the combi started misbehaving in a different way. So the combi is switched off and all hot water is coming from the Thermino heat battery. I have been tuning this alternate mode which I had only created as a thought experiment, but seems to have largely worked.
Thus, no gas use for the last week, and no space heating.
The Enphase emailed monthly report for September (received 2022-10-18) says: produced (generated) 307.4kWh (max 17.3kWh on the 17th), consumed 237.7kWh (max 12.5kWh on the 29th), grid energy imported 30.0kWh and exported 79.8kWh, energy independence 87% (max 97% on the 7th).
HDD12=13 vs 4 last September.
2022-10 249 (8.0/d) -202 (-6.5/d) 29 (0.9/d) 20220930T17:15Z to 20221031T17:57Z (31d) Meter readings: electricity generation 202.4kWh, export 28.6kWh, import 75.3kWh (thus net consumption (I+G-E) 249.1kWh, self consumption ((N-I)/N) 67%); gas ~2.65m^3 (so 29.3kWh @ 11.1kWh/m^3).
The combi was fixed on the afternoon of the 4th, and returned to being our primary source of DHW.
This month there has been little PV diversion to the Thermino as expected, but sometimes low-carbon grid electricity available in the wee hours. So electricity imports are up, still keeping gas imports down.
The Enphase emailed monthly report for October (received 2022-11-12) says: produced (generated) 203.1kWh (max 10.9kWh on the 6th), consumed 232.3kWh (max 11.8kWh on the 24th), grid energy imported 75.7kWh and exported 26.2kWh, energy independence 67% (max 94% on the 2nd).
HDD12=17 vs 23 last October.
2022-11 250 (8.3/d) -76 (-2.5/d) 58 (1.9/d) 20221031T17:57Z to 20221130T18:04Z (30d) Meter readings: electricity generation 75.8kWh, export 1.0kWh, import 175.6kWh (thus net consumption (I+G-E) 250.4kWh, self consumption ((N-I)/N) 30%); gas ~5.23m^3 (so 58.1kWh @ 11.1kWh/m^3).
The combi was thoroughly serviced on the afternoon of the 17th.
This month there has been essentially no PV diversion to the Thermino. There have been a fair few nights with low-carbon grid electricity, with 6kWh+ top-ups overnight. So gas demand for DHW has been about half what would be otherwise expected. Heating was not on this month.
The Enphase emailed monthly report for November (received 2022-12-14) says: produced (generated) 76.6kWh (max 5.0kWh on the 4th), consumed 234.4kWh (max 13.3kWh on the 24th), grid energy imported 174.1kWh and exported 0.6kWh, energy independence 25% (max 76% on the 12th).
HDD12=65 vs 121 last November.
2022-12 241 (7.8/d) -47 (-1.5/d) 600 (19/d) 20221130T18:04Z to 20221231T18:04Z (31d) Meter readings: electricity generation 46.7kWh, export 0.3kWh, import 195.0kWh (thus net consumption (I+G-E) 241.4kWh, self consumption ((N-I)/N) 19%); gas ~54.04m^3 (so 599.8kWh @ 11.1kWh/m^3).
December was cold (highest HDD12 since 2010 at 328; 2008 and 2009 also higher). So gas demand, even though reduced via low-grid-intensity heat-battery magic, was a moderately typical 19kWh/d. (From March to November gas consumption was well below typical.) HDD12=219 vs 134 last December.
2022 total (Jan--Dec) 2998 (8.21/d) -3925 (-10.8/d) 2074 (5.68/d) 20211231T18:16Z to 20221231T18:04Z (365d) HDD of 839 (vs 1029 for 2021), below the 2008 to 2020 mean of 984.
Gas consumption down to 2074kWh, lowest ever, reduced via the eddi/Thermino. Reasonable PV generation (3925kWh); better than 2021, but not up to 2020 record! Gross electricity consumption (minus heat, conexDHW) high ~2155kWh, close to 2020 lockdown record of 2365kWh, likely because of overhead of expanded Enphase and new eddi/Thermino systems. Imports at 832kWh are relatively low, in spite of heat-battery grid top-ups (201kWh, vs 642kWh diverted). Exports at 1759kWh are the lowest since 2010, because of diversion to DHW. Self-consumption calculated as (N-Imp)/N was 72%. Total grid flows (import+export) at record low of 2591kWh.
kgCO2 1289kg (3.5/d) -1688kg (-4.6/d) 394kg (1.1/d) ~-0.005tCO2 [though see below] (~-0.01kgCO2/d) gas/electricity emissions total for 4 people, based on fixed 0.43kgCO2/kWh for electricity (netted) and 0.19kgCO2/kWh for gas, ie slightly carbon negative.
We did not fly this year and still do not own a car.
With data from the Enphase metering and the FUELINST log I compute a potentially more accurate CO2 electricity balance, noting the relatively low carbon grid intensity when exporting summer PV and high intensity when importing in winter. (There is still the argument that any balancing at the moment may be done by a gas turbine in practice.) See below for the computations — the estimated figure is now a slightly positive 0.149tCO2 (-0.245(e) + 0.394(g)) overall for gas and electricity.

2022: ToD Carbon Calculation

(See calculation with workings from 2020.)

Calculating carbon emissions by time-of-day (ToD) involves the FUELINST data from Elexon / National Grid, and the locally sampled 16WW grid import/export flows using the Enphase system.

% sh script/analytic/ 2022
Created/updated out/yearly/Enphase-1h-2022.csv.gz
Created/updated out/yearly/FUELINST-1h-2022.csv.gz
Unique hours in data:     8760
Created/updated out/yearly/Enphase-join-FUELINST-1h-2022.csv.gz
Unique hours in joined data:     8678
Scale factor to allow for missing data: 1.00945
Raw 16WW electricity CO2 kg for 2022: -242.815
Adjusted 16WW electricity CO2 kg for 2022: -245.11

That seems to be an effective (weighted) grid intensity of 264gCO2/kWh.