Small suppliers continue to lead the way when it comes to customer service, taking four of the top five spots in our latest customer service poll rankings.

Gas-only supplier Zog Energy and Octopus Energy came in joint top, followed by fellow minnows Bulb and Tonik. Zog, which has around 9,500 customers - after adding around 2,500 in the last year, scored 94% 'great ' for service, while Octopus, with a 93% 'great' rating, has around 220,000, up nearly 100,000 in the last year.

The only big(ish) name in our top five is Ovo Energy, which came in fifth for the second time in a row after being knocked off second spot by the smaller suppliers.

If you're looking to switch energy providers you can do a full comparison via our Cheap Energy Club and filter results to show only those with a certain rating, based on our service polls.

Small suppliers outperform big six - but they're not always better

Our latest results show a mixed bag for smaller suppliers - with some offering top customer service, while others are clearly struggling to cope. Small suppliers took four of the top five spots in our latest poll, but at the other end also accounted for the bottom two spots.

At the bottom of the table, Green Star Energy - a new supplier in our rankings - took second-last place, just ahead of Iresa.

It's no real surprise Iresa took bottom spot - with only 19% rating in 'great' and a massive 67% 'poor' - given the issues many Iresa customers have experienced, leading energy regulator Ofgem to actually ban it from taking on new customers until its service improves.

With small suppliers currently offering much cheaper tariffs, for the most part, than the big names, it's important to check feedback when doing a comparison to avoid the worst offenders when it comes to customers service. You can use our 'Superb' and 'Good or Better' filters on our Cheap Energy Club to only see firms with decent service, based on these poll results.

When it comes the big six, most actually improved - at least in terms of rankings compared to our last poll. SSE performed the best, jumping three places to seventh in our list. Npower, Scottish Power and British Gas, clawed their way off the bottom of the table this time.

Despite this, SSE was the only big six supplier that actually saw an improvement in the 'great' service score - British Gas, EDF, and Npower all saw theirs fall, while E.on and Scottish Power's 'great' rating remained the same as last time.

MoneySavingExpert carries out an energy firm customer service poll twice a year, and ranks all providers attracting at least 100 votes. Over 4,000 users took part in our May 2018 poll.

The results in full

Here is the full table of results from our latest energy company service poll:

Energy company service rating, May 2018(results and ranking from November 2017 in brackets)

Rank Provider 'Great' 'OK' 'Poor'
1 (3) Octopus Energy 93% (90%) 6% (6%) 1% (3%)
1 (-) Zog Energy 94% (96%) 4% (2%) 2% (2%)
3 (2) Bulb 90% (95%) 8% (3%) 3% (2%)
4 (4) Tonik Energy 76% (86%) 17% (10%) 7% (5%)
5 (5) Ovo Energy 76% (80%) 16% (16%) 9% (5%)
6 (6) Avro Energy 66% (73%) 26% (20%) 7% (7%)
7 (10) SSE (i) 53% (44%) 31% (35%) 16% (21%)
8 (7) First Utility 53% (60%) 26% (24%) 22% (16%)
9 (9) EDF 43% (46%) 34% (34%) 23% (19%)
10 (11) Flow Energy 48% (44%) 20% (22%) 32% (34%)
11 (13) E.on 36% (36%) 42% (36%) 22% (28%)
12 (15) British Gas 28% (30%) 41% (33%) 32% (37%)
13 (16) Scottish Power 29% (29%) 30% (31%) 41% (41%)
14 (17) Npower 23% (27%) 31% (31%) 46% (41%)
15 (-) Green Star Energy 26% (-) 22% (-) 52% (-)
16 (14) Iresa 19% (39%) 14% (17%) 67% (44%)
Order calculated by 0 points for 'poor', 1 for 'OK' and 2 for 'great'. 4,305 votes in total – we've ignored providers with fewer than 100 votes. The percentages may not add up to 100% owing to rounding. (i) Includes Atlantic, Scottish Hydro, Southern Electric and Swalec.

What the energy firms say

A spokesperson for Green Star Energy said: "We are disappointed to appear in the lower rankings of this survey. We value our customers and remain committed to improving their experience when dealing with us. We are investing heavily in reducing call waiting times, training our call centre agents and making it easier for our customers to deal with Green Star Energy on their terms and within their timeframes.

"We are dedicated to listening to customers’ needs and plan to take ongoing action to ensure we reach a position at which we are exceeding their expectations."

We asked Iresa for a comment on our poll but have yet to hear back.