Earth Notes: Saving Electricity and Gas (2022)

Updated 2022-08-12 10:11 GMT.
By Damon Hart-Davis.
Meter readings and energy-saving notes for dual fuel use at home in 2022. #4kWhDHWClub
20220215 heatBatTarget
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 myenegi 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 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've 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 myenergy eddi solar diverter was wired in at the end of the month. and this was running part of the month. But the Themino heat battery was not there to receive energy, so 0kWh/d electricity used for DHW of which 0kWh diverted and 0kWh boosted.
We've 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.
~1562 words.